| Message ID | 20200629140938.17566-4-drjones@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | hw/arm/virt-acpi-build: Only expose flash on older machine types | expand |
On 6/29/20 4:09 PM, Andrew Jones wrote: > The flash device is exclusively for the host-controlled firmware, so > we should not expose it to the OS. Exposing it risks the OS messing > with it, which could break firmware runtime services and surprise the > OS when all its changes disappear after reboot. > > As firmware needs the device and uses DT, we leave the device exposed > there. It's up to firmware to remove the nodes from DT before sending > it on to the OS. However, there's no need to force firmware to remove > tables from ACPI (which it doesn't know how to do anyway), so we > simply don't add the tables in the first place. But, as we've been > adding the tables for quite some time and don't want to change the > default hardware exposed to versioned machines, then we only stop > exposing the flash device tables for 5.1 and later machine types. > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com> > Suggested-by: Laszlo Ersek <lersek@redhat.com> > Signed-off-by: Andrew Jones <drjones@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> > --- > hw/arm/virt-acpi-build.c | 5 ++++- > hw/arm/virt.c | 3 +++ > include/hw/arm/virt.h | 1 + > 3 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c > index 1384a2cf2ab4..91f0df7b13a3 100644 > --- a/hw/arm/virt-acpi-build.c > +++ b/hw/arm/virt-acpi-build.c > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker, > static void > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > { > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms); > Aml *scope, *dsdt; > MachineState *ms = MACHINE(vms); > const MemMapEntry *memmap = vms->memmap; > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > acpi_dsdt_add_cpus(scope, vms->smp_cpus); > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART], > (irqmap[VIRT_UART] + ARM_SPI_BASE)); > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > + if (vmc->acpi_expose_flash) { > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > + } > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]); > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO], > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS); > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > index cd0834ce7faf..5adc9ff799ef 100644 > --- a/hw/arm/virt.c > +++ b/hw/arm/virt.c > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1) > > static void virt_machine_5_0_options(MachineClass *mc) > { > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc)); > + > virt_machine_5_1_options(mc); > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len); > mc->numa_mem_supported = true; > + vmc->acpi_expose_flash = true; > } > DEFINE_VIRT_MACHINE(5, 0) > > diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h > index 31878ddc7223..c65be5fe0bb6 100644 > --- a/include/hw/arm/virt.h > +++ b/include/hw/arm/virt.h > @@ -119,6 +119,7 @@ typedef struct { > bool no_highmem_ecam; > bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */ > bool kvm_no_adjvtime; > + bool acpi_expose_flash; > } VirtMachineClass; > > typedef struct { >
On 06/29/20 16:09, Andrew Jones wrote: > The flash device is exclusively for the host-controlled firmware, so > we should not expose it to the OS. Exposing it risks the OS messing > with it, which could break firmware runtime services and surprise the > OS when all its changes disappear after reboot. > > As firmware needs the device and uses DT, we leave the device exposed > there. It's up to firmware to remove the nodes from DT before sending > it on to the OS. However, there's no need to force firmware to remove > tables from ACPI (which it doesn't know how to do anyway), so we > simply don't add the tables in the first place. But, as we've been > adding the tables for quite some time and don't want to change the > default hardware exposed to versioned machines, then we only stop > exposing the flash device tables for 5.1 and later machine types. > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com> > Suggested-by: Laszlo Ersek <lersek@redhat.com> > Signed-off-by: Andrew Jones <drjones@redhat.com> > --- > hw/arm/virt-acpi-build.c | 5 ++++- > hw/arm/virt.c | 3 +++ > include/hw/arm/virt.h | 1 + > 3 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c > index 1384a2cf2ab4..91f0df7b13a3 100644 > --- a/hw/arm/virt-acpi-build.c > +++ b/hw/arm/virt-acpi-build.c > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker, > static void > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > { > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms); > Aml *scope, *dsdt; > MachineState *ms = MACHINE(vms); > const MemMapEntry *memmap = vms->memmap; > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > acpi_dsdt_add_cpus(scope, vms->smp_cpus); > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART], > (irqmap[VIRT_UART] + ARM_SPI_BASE)); > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > + if (vmc->acpi_expose_flash) { > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > + } > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]); > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO], > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS); > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > index cd0834ce7faf..5adc9ff799ef 100644 > --- a/hw/arm/virt.c > +++ b/hw/arm/virt.c > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1) > > static void virt_machine_5_0_options(MachineClass *mc) > { > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc)); > + > virt_machine_5_1_options(mc); > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len); > mc->numa_mem_supported = true; > + vmc->acpi_expose_flash = true; > } > DEFINE_VIRT_MACHINE(5, 0) > > diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h > index 31878ddc7223..c65be5fe0bb6 100644 > --- a/include/hw/arm/virt.h > +++ b/include/hw/arm/virt.h > @@ -119,6 +119,7 @@ typedef struct { > bool no_highmem_ecam; > bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */ > bool kvm_no_adjvtime; > + bool acpi_expose_flash; > } VirtMachineClass; > > typedef struct { > Reviewed-by: Laszlo Ersek <lersek@redhat.com> Thank you! Laszlo
On Mon, Jun 29, 2020 at 04:09:37PM +0200, Andrew Jones wrote: > The flash device is exclusively for the host-controlled firmware, so > we should not expose it to the OS. Exposing it risks the OS messing > with it, which could break firmware runtime services and surprise the > OS when all its changes disappear after reboot. > > As firmware needs the device and uses DT, we leave the device exposed > there. It's up to firmware to remove the nodes from DT before sending > it on to the OS. However, there's no need to force firmware to remove > tables from ACPI (which it doesn't know how to do anyway), so we > simply don't add the tables in the first place. But, as we've been > adding the tables for quite some time and don't want to change the > default hardware exposed to versioned machines, then we only stop > exposing the flash device tables for 5.1 and later machine types. > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com> > Suggested-by: Laszlo Ersek <lersek@redhat.com> > Signed-off-by: Andrew Jones <drjones@redhat.com> So who's merging this? Mostly ACPI things so I guess my tree? If so can I get acks from ARM maintainers pls? Thanks! > --- > hw/arm/virt-acpi-build.c | 5 ++++- > hw/arm/virt.c | 3 +++ > include/hw/arm/virt.h | 1 + > 3 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c > index 1384a2cf2ab4..91f0df7b13a3 100644 > --- a/hw/arm/virt-acpi-build.c > +++ b/hw/arm/virt-acpi-build.c > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker, > static void > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > { > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms); > Aml *scope, *dsdt; > MachineState *ms = MACHINE(vms); > const MemMapEntry *memmap = vms->memmap; > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > acpi_dsdt_add_cpus(scope, vms->smp_cpus); > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART], > (irqmap[VIRT_UART] + ARM_SPI_BASE)); > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > + if (vmc->acpi_expose_flash) { > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > + } > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]); > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO], > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS); > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > index cd0834ce7faf..5adc9ff799ef 100644 > --- a/hw/arm/virt.c > +++ b/hw/arm/virt.c > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1) > > static void virt_machine_5_0_options(MachineClass *mc) > { > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc)); > + > virt_machine_5_1_options(mc); > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len); > mc->numa_mem_supported = true; > + vmc->acpi_expose_flash = true; > } > DEFINE_VIRT_MACHINE(5, 0) > > diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h > index 31878ddc7223..c65be5fe0bb6 100644 > --- a/include/hw/arm/virt.h > +++ b/include/hw/arm/virt.h > @@ -119,6 +119,7 @@ typedef struct { > bool no_highmem_ecam; > bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */ > bool kvm_no_adjvtime; > + bool acpi_expose_flash; > } VirtMachineClass; > > typedef struct { > -- > 2.25.4
On Thu, 2 Jul 2020 at 10:53, Michael S. Tsirkin <mst@redhat.com> wrote: > > On Mon, Jun 29, 2020 at 04:09:37PM +0200, Andrew Jones wrote: > > The flash device is exclusively for the host-controlled firmware, so > > we should not expose it to the OS. Exposing it risks the OS messing > > with it, which could break firmware runtime services and surprise the > > OS when all its changes disappear after reboot. > > > > As firmware needs the device and uses DT, we leave the device exposed > > there. It's up to firmware to remove the nodes from DT before sending > > it on to the OS. However, there's no need to force firmware to remove > > tables from ACPI (which it doesn't know how to do anyway), so we > > simply don't add the tables in the first place. But, as we've been > > adding the tables for quite some time and don't want to change the > > default hardware exposed to versioned machines, then we only stop > > exposing the flash device tables for 5.1 and later machine types. > > > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com> > > Suggested-by: Laszlo Ersek <lersek@redhat.com> > > Signed-off-by: Andrew Jones <drjones@redhat.com> > > So who's merging this? Mostly ACPI things so I guess my tree? > If so can I get acks from ARM maintainers pls? This is on my to-look-at queue but in theory I'm on holiday this week :-) -- PMM
On Thu, Jul 02, 2020 at 11:16:03AM +0100, Peter Maydell wrote: > On Thu, 2 Jul 2020 at 10:53, Michael S. Tsirkin <mst@redhat.com> wrote: > > > > On Mon, Jun 29, 2020 at 04:09:37PM +0200, Andrew Jones wrote: > > > The flash device is exclusively for the host-controlled firmware, so > > > we should not expose it to the OS. Exposing it risks the OS messing > > > with it, which could break firmware runtime services and surprise the > > > OS when all its changes disappear after reboot. > > > > > > As firmware needs the device and uses DT, we leave the device exposed > > > there. It's up to firmware to remove the nodes from DT before sending > > > it on to the OS. However, there's no need to force firmware to remove > > > tables from ACPI (which it doesn't know how to do anyway), so we > > > simply don't add the tables in the first place. But, as we've been > > > adding the tables for quite some time and don't want to change the > > > default hardware exposed to versioned machines, then we only stop > > > exposing the flash device tables for 5.1 and later machine types. > > > > > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com> > > > Suggested-by: Laszlo Ersek <lersek@redhat.com> > > > Signed-off-by: Andrew Jones <drjones@redhat.com> > > > > So who's merging this? Mostly ACPI things so I guess my tree? > > If so can I get acks from ARM maintainers pls? > > This is on my to-look-at queue but in theory I'm on holiday this week :-) > > -- PMM I picked up patch 1 for now :)
On Mon, 29 Jun 2020 16:09:37 +0200 Andrew Jones <drjones@redhat.com> wrote: > The flash device is exclusively for the host-controlled firmware, so > we should not expose it to the OS. Exposing it risks the OS messing > with it, which could break firmware runtime services and surprise the > OS when all its changes disappear after reboot. > > As firmware needs the device and uses DT, we leave the device exposed > there. It's up to firmware to remove the nodes from DT before sending > it on to the OS. However, there's no need to force firmware to remove > tables from ACPI (which it doesn't know how to do anyway), so we > simply don't add the tables in the first place. But, as we've been > adding the tables for quite some time and don't want to change the > default hardware exposed to versioned machines, then we only stop > exposing the flash device tables for 5.1 and later machine types. > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com> > Suggested-by: Laszlo Ersek <lersek@redhat.com> > Signed-off-by: Andrew Jones <drjones@redhat.com> > --- > hw/arm/virt-acpi-build.c | 5 ++++- > hw/arm/virt.c | 3 +++ > include/hw/arm/virt.h | 1 + > 3 files changed, 8 insertions(+), 1 deletion(-) > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c > index 1384a2cf2ab4..91f0df7b13a3 100644 > --- a/hw/arm/virt-acpi-build.c > +++ b/hw/arm/virt-acpi-build.c > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker, > static void > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > { > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms); > Aml *scope, *dsdt; > MachineState *ms = MACHINE(vms); > const MemMapEntry *memmap = vms->memmap; > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > acpi_dsdt_add_cpus(scope, vms->smp_cpus); > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART], > (irqmap[VIRT_UART] + ARM_SPI_BASE)); > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > + if (vmc->acpi_expose_flash) { > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > + } > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]); > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO], > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS); > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > index cd0834ce7faf..5adc9ff799ef 100644 > --- a/hw/arm/virt.c > +++ b/hw/arm/virt.c > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1) > > static void virt_machine_5_0_options(MachineClass *mc) > { > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc)); > + > virt_machine_5_1_options(mc); > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len); > mc->numa_mem_supported = true; > + vmc->acpi_expose_flash = true; we usually do not version ACPI tables changes (unless we have a good reason to do so) > } > DEFINE_VIRT_MACHINE(5, 0) > > diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h > index 31878ddc7223..c65be5fe0bb6 100644 > --- a/include/hw/arm/virt.h > +++ b/include/hw/arm/virt.h > @@ -119,6 +119,7 @@ typedef struct { > bool no_highmem_ecam; > bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */ > bool kvm_no_adjvtime; > + bool acpi_expose_flash; > } VirtMachineClass; > > typedef struct {
On Mon, Jul 13, 2020 at 10:49:07AM +0200, Igor Mammedov wrote: > On Mon, 29 Jun 2020 16:09:37 +0200 > Andrew Jones <drjones@redhat.com> wrote: > > > The flash device is exclusively for the host-controlled firmware, so > > we should not expose it to the OS. Exposing it risks the OS messing > > with it, which could break firmware runtime services and surprise the > > OS when all its changes disappear after reboot. > > > > As firmware needs the device and uses DT, we leave the device exposed > > there. It's up to firmware to remove the nodes from DT before sending > > it on to the OS. However, there's no need to force firmware to remove > > tables from ACPI (which it doesn't know how to do anyway), so we > > simply don't add the tables in the first place. But, as we've been > > adding the tables for quite some time and don't want to change the > > default hardware exposed to versioned machines, then we only stop > > exposing the flash device tables for 5.1 and later machine types. > > > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com> > > Suggested-by: Laszlo Ersek <lersek@redhat.com> > > Signed-off-by: Andrew Jones <drjones@redhat.com> > > --- > > hw/arm/virt-acpi-build.c | 5 ++++- > > hw/arm/virt.c | 3 +++ > > include/hw/arm/virt.h | 1 + > > 3 files changed, 8 insertions(+), 1 deletion(-) > > > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c > > index 1384a2cf2ab4..91f0df7b13a3 100644 > > --- a/hw/arm/virt-acpi-build.c > > +++ b/hw/arm/virt-acpi-build.c > > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker, > > static void > > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > > { > > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms); > > Aml *scope, *dsdt; > > MachineState *ms = MACHINE(vms); > > const MemMapEntry *memmap = vms->memmap; > > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > > acpi_dsdt_add_cpus(scope, vms->smp_cpus); > > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART], > > (irqmap[VIRT_UART] + ARM_SPI_BASE)); > > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > > + if (vmc->acpi_expose_flash) { > > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > > + } > > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]); > > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO], > > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS); > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > > index cd0834ce7faf..5adc9ff799ef 100644 > > --- a/hw/arm/virt.c > > +++ b/hw/arm/virt.c > > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1) > > > > static void virt_machine_5_0_options(MachineClass *mc) > > { > > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc)); > > + > > virt_machine_5_1_options(mc); > > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len); > > mc->numa_mem_supported = true; > > + vmc->acpi_expose_flash = true; > > we usually do not version ACPI tables changes > (unless we have a good reason to do so) Even when the change is to remove the exposure of hardware from the guest? Before this change, if a guest looked, it had a flash, after this change, if a guest looks, it doesn't. I'd feel much better versioning a change like that, than not. Thanks, drew > > > } > > DEFINE_VIRT_MACHINE(5, 0) > > > > diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h > > index 31878ddc7223..c65be5fe0bb6 100644 > > --- a/include/hw/arm/virt.h > > +++ b/include/hw/arm/virt.h > > @@ -119,6 +119,7 @@ typedef struct { > > bool no_highmem_ecam; > > bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */ > > bool kvm_no_adjvtime; > > + bool acpi_expose_flash; > > } VirtMachineClass; > > > > typedef struct { > >
On Tue, Jul 14, 2020 at 07:51:09AM +0200, Andrew Jones wrote: > On Mon, Jul 13, 2020 at 10:49:07AM +0200, Igor Mammedov wrote: > > On Mon, 29 Jun 2020 16:09:37 +0200 > > Andrew Jones <drjones@redhat.com> wrote: > > > > > The flash device is exclusively for the host-controlled firmware, so > > > we should not expose it to the OS. Exposing it risks the OS messing > > > with it, which could break firmware runtime services and surprise the > > > OS when all its changes disappear after reboot. > > > > > > As firmware needs the device and uses DT, we leave the device exposed > > > there. It's up to firmware to remove the nodes from DT before sending > > > it on to the OS. However, there's no need to force firmware to remove > > > tables from ACPI (which it doesn't know how to do anyway), so we > > > simply don't add the tables in the first place. But, as we've been > > > adding the tables for quite some time and don't want to change the > > > default hardware exposed to versioned machines, then we only stop > > > exposing the flash device tables for 5.1 and later machine types. > > > > > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com> > > > Suggested-by: Laszlo Ersek <lersek@redhat.com> > > > Signed-off-by: Andrew Jones <drjones@redhat.com> > > > --- > > > hw/arm/virt-acpi-build.c | 5 ++++- > > > hw/arm/virt.c | 3 +++ > > > include/hw/arm/virt.h | 1 + > > > 3 files changed, 8 insertions(+), 1 deletion(-) > > > > > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c > > > index 1384a2cf2ab4..91f0df7b13a3 100644 > > > --- a/hw/arm/virt-acpi-build.c > > > +++ b/hw/arm/virt-acpi-build.c > > > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker, > > > static void > > > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > > > { > > > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms); > > > Aml *scope, *dsdt; > > > MachineState *ms = MACHINE(vms); > > > const MemMapEntry *memmap = vms->memmap; > > > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > > > acpi_dsdt_add_cpus(scope, vms->smp_cpus); > > > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART], > > > (irqmap[VIRT_UART] + ARM_SPI_BASE)); > > > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > > > + if (vmc->acpi_expose_flash) { > > > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > > > + } > > > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]); > > > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO], > > > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS); > > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > > > index cd0834ce7faf..5adc9ff799ef 100644 > > > --- a/hw/arm/virt.c > > > +++ b/hw/arm/virt.c > > > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1) > > > > > > static void virt_machine_5_0_options(MachineClass *mc) > > > { > > > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc)); > > > + > > > virt_machine_5_1_options(mc); > > > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len); > > > mc->numa_mem_supported = true; > > > + vmc->acpi_expose_flash = true; > > > > we usually do not version ACPI tables changes > > (unless we have a good reason to do so) > > Even when the change is to remove the exposure of hardware from the guest? > Before this change, if a guest looked, it had a flash, after this change, > if a guest looks, it doesn't. It's up to the relevant maintainers who know what the semantics are. FYI ACPI tables only change across a reset though. So it's a question of whether guests get confused even if this changes after a reboot. Versioning is generally safer, but it's a good idea to document the motivation for it. > I'd feel much better versioning a change > like that, than not. > > Thanks, > drew > > > > > > } > > > DEFINE_VIRT_MACHINE(5, 0) > > > > > > diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h > > > index 31878ddc7223..c65be5fe0bb6 100644 > > > --- a/include/hw/arm/virt.h > > > +++ b/include/hw/arm/virt.h > > > @@ -119,6 +119,7 @@ typedef struct { > > > bool no_highmem_ecam; > > > bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */ > > > bool kvm_no_adjvtime; > > > + bool acpi_expose_flash; > > > } VirtMachineClass; > > > > > > typedef struct { > > > >
On Tue, Jul 14, 2020 at 04:57:50AM -0400, Michael S. Tsirkin wrote: > On Tue, Jul 14, 2020 at 07:51:09AM +0200, Andrew Jones wrote: > > On Mon, Jul 13, 2020 at 10:49:07AM +0200, Igor Mammedov wrote: > > > On Mon, 29 Jun 2020 16:09:37 +0200 > > > Andrew Jones <drjones@redhat.com> wrote: > > > > > > > The flash device is exclusively for the host-controlled firmware, so > > > > we should not expose it to the OS. Exposing it risks the OS messing > > > > with it, which could break firmware runtime services and surprise the > > > > OS when all its changes disappear after reboot. > > > > > > > > As firmware needs the device and uses DT, we leave the device exposed > > > > there. It's up to firmware to remove the nodes from DT before sending > > > > it on to the OS. However, there's no need to force firmware to remove > > > > tables from ACPI (which it doesn't know how to do anyway), so we > > > > simply don't add the tables in the first place. But, as we've been > > > > adding the tables for quite some time and don't want to change the > > > > default hardware exposed to versioned machines, then we only stop > > > > exposing the flash device tables for 5.1 and later machine types. > > > > > > > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com> > > > > Suggested-by: Laszlo Ersek <lersek@redhat.com> > > > > Signed-off-by: Andrew Jones <drjones@redhat.com> > > > > --- > > > > hw/arm/virt-acpi-build.c | 5 ++++- > > > > hw/arm/virt.c | 3 +++ > > > > include/hw/arm/virt.h | 1 + > > > > 3 files changed, 8 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c > > > > index 1384a2cf2ab4..91f0df7b13a3 100644 > > > > --- a/hw/arm/virt-acpi-build.c > > > > +++ b/hw/arm/virt-acpi-build.c > > > > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker, > > > > static void > > > > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > > > > { > > > > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms); > > > > Aml *scope, *dsdt; > > > > MachineState *ms = MACHINE(vms); > > > > const MemMapEntry *memmap = vms->memmap; > > > > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > > > > acpi_dsdt_add_cpus(scope, vms->smp_cpus); > > > > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART], > > > > (irqmap[VIRT_UART] + ARM_SPI_BASE)); > > > > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > > > > + if (vmc->acpi_expose_flash) { > > > > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > > > > + } > > > > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]); > > > > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO], > > > > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS); > > > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > > > > index cd0834ce7faf..5adc9ff799ef 100644 > > > > --- a/hw/arm/virt.c > > > > +++ b/hw/arm/virt.c > > > > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1) > > > > > > > > static void virt_machine_5_0_options(MachineClass *mc) > > > > { > > > > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc)); > > > > + > > > > virt_machine_5_1_options(mc); > > > > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len); > > > > mc->numa_mem_supported = true; > > > > + vmc->acpi_expose_flash = true; > > > > > > we usually do not version ACPI tables changes > > > (unless we have a good reason to do so) > > > > Even when the change is to remove the exposure of hardware from the guest? > > Before this change, if a guest looked, it had a flash, after this change, > > if a guest looks, it doesn't. > > It's up to the relevant maintainers who know what the semantics are. > FYI ACPI tables only change across a reset though. > So it's a question of whether guests get confused even if this > changes after a reboot. Yup, but it's still the same "machine", so a user may wonder why it changed. > Versioning is generally safer, but it's a good idea to document > the motivation for it. > Well, in this case, we could probably push this change to old machine types and nobody would notice. If a guest is using ACPI, then it must be using firmware, and if they're using firmware, then they can't be using the flash. So the user shouldn't care if it's there or not. The only justification for the versioning is because "it's safer". If people feel strongly about avoiding versioning when it's not obviously necessary, then I can respin without it. Thanks, drew
On Tue, Jul 14, 2020 at 11:23:25AM +0200, Andrew Jones wrote: > On Tue, Jul 14, 2020 at 04:57:50AM -0400, Michael S. Tsirkin wrote: > > On Tue, Jul 14, 2020 at 07:51:09AM +0200, Andrew Jones wrote: > > > On Mon, Jul 13, 2020 at 10:49:07AM +0200, Igor Mammedov wrote: > > > > On Mon, 29 Jun 2020 16:09:37 +0200 > > > > Andrew Jones <drjones@redhat.com> wrote: > > > > > > > > > The flash device is exclusively for the host-controlled firmware, so > > > > > we should not expose it to the OS. Exposing it risks the OS messing > > > > > with it, which could break firmware runtime services and surprise the > > > > > OS when all its changes disappear after reboot. > > > > > > > > > > As firmware needs the device and uses DT, we leave the device exposed > > > > > there. It's up to firmware to remove the nodes from DT before sending > > > > > it on to the OS. However, there's no need to force firmware to remove > > > > > tables from ACPI (which it doesn't know how to do anyway), so we > > > > > simply don't add the tables in the first place. But, as we've been > > > > > adding the tables for quite some time and don't want to change the > > > > > default hardware exposed to versioned machines, then we only stop > > > > > exposing the flash device tables for 5.1 and later machine types. > > > > > > > > > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com> > > > > > Suggested-by: Laszlo Ersek <lersek@redhat.com> > > > > > Signed-off-by: Andrew Jones <drjones@redhat.com> > > > > > --- > > > > > hw/arm/virt-acpi-build.c | 5 ++++- > > > > > hw/arm/virt.c | 3 +++ > > > > > include/hw/arm/virt.h | 1 + > > > > > 3 files changed, 8 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c > > > > > index 1384a2cf2ab4..91f0df7b13a3 100644 > > > > > --- a/hw/arm/virt-acpi-build.c > > > > > +++ b/hw/arm/virt-acpi-build.c > > > > > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker, > > > > > static void > > > > > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > > > > > { > > > > > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms); > > > > > Aml *scope, *dsdt; > > > > > MachineState *ms = MACHINE(vms); > > > > > const MemMapEntry *memmap = vms->memmap; > > > > > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > > > > > acpi_dsdt_add_cpus(scope, vms->smp_cpus); > > > > > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART], > > > > > (irqmap[VIRT_UART] + ARM_SPI_BASE)); > > > > > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > > > > > + if (vmc->acpi_expose_flash) { > > > > > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > > > > > + } > > > > > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]); > > > > > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO], > > > > > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS); > > > > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > > > > > index cd0834ce7faf..5adc9ff799ef 100644 > > > > > --- a/hw/arm/virt.c > > > > > +++ b/hw/arm/virt.c > > > > > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1) > > > > > > > > > > static void virt_machine_5_0_options(MachineClass *mc) > > > > > { > > > > > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc)); > > > > > + > > > > > virt_machine_5_1_options(mc); > > > > > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len); > > > > > mc->numa_mem_supported = true; > > > > > + vmc->acpi_expose_flash = true; > > > > > > > > we usually do not version ACPI tables changes > > > > (unless we have a good reason to do so) > > > > > > Even when the change is to remove the exposure of hardware from the guest? > > > Before this change, if a guest looked, it had a flash, after this change, > > > if a guest looks, it doesn't. > > > > It's up to the relevant maintainers who know what the semantics are. > > FYI ACPI tables only change across a reset though. > > So it's a question of whether guests get confused even if this > > changes after a reboot. > > Yup, but it's still the same "machine", so a user may wonder why it > changed. > > > Versioning is generally safer, but it's a good idea to document > > the motivation for it. > > > > Well, in this case, we could probably push this change to old machine > types and nobody would notice. If a guest is using ACPI, then it must > be using firmware, and if they're using firmware, then they can't be > using the flash. So the user shouldn't care if it's there or not. The > only justification for the versioning is because "it's safer". If > people feel strongly about avoiding versioning when it's not obviously > necessary, then I can respin without it. > > Thanks, > drew It's up to maintainers either way, but please do tweak the motivation in the commit log to include the above.
On Tue, 14 Jul 2020 11:23:25 +0200 Andrew Jones <drjones@redhat.com> wrote: > On Tue, Jul 14, 2020 at 04:57:50AM -0400, Michael S. Tsirkin wrote: > > On Tue, Jul 14, 2020 at 07:51:09AM +0200, Andrew Jones wrote: > > > On Mon, Jul 13, 2020 at 10:49:07AM +0200, Igor Mammedov wrote: > > > > On Mon, 29 Jun 2020 16:09:37 +0200 > > > > Andrew Jones <drjones@redhat.com> wrote: > > > > > > > > > The flash device is exclusively for the host-controlled firmware, so > > > > > we should not expose it to the OS. Exposing it risks the OS messing > > > > > with it, which could break firmware runtime services and surprise the > > > > > OS when all its changes disappear after reboot. > > > > > > > > > > As firmware needs the device and uses DT, we leave the device exposed > > > > > there. It's up to firmware to remove the nodes from DT before sending > > > > > it on to the OS. However, there's no need to force firmware to remove > > > > > tables from ACPI (which it doesn't know how to do anyway), so we > > > > > simply don't add the tables in the first place. But, as we've been > > > > > adding the tables for quite some time and don't want to change the > > > > > default hardware exposed to versioned machines, then we only stop > > > > > exposing the flash device tables for 5.1 and later machine types. > > > > > > > > > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com> > > > > > Suggested-by: Laszlo Ersek <lersek@redhat.com> > > > > > Signed-off-by: Andrew Jones <drjones@redhat.com> > > > > > --- > > > > > hw/arm/virt-acpi-build.c | 5 ++++- > > > > > hw/arm/virt.c | 3 +++ > > > > > include/hw/arm/virt.h | 1 + > > > > > 3 files changed, 8 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c > > > > > index 1384a2cf2ab4..91f0df7b13a3 100644 > > > > > --- a/hw/arm/virt-acpi-build.c > > > > > +++ b/hw/arm/virt-acpi-build.c > > > > > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker, > > > > > static void > > > > > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > > > > > { > > > > > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms); > > > > > Aml *scope, *dsdt; > > > > > MachineState *ms = MACHINE(vms); > > > > > const MemMapEntry *memmap = vms->memmap; > > > > > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > > > > > acpi_dsdt_add_cpus(scope, vms->smp_cpus); > > > > > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART], > > > > > (irqmap[VIRT_UART] + ARM_SPI_BASE)); > > > > > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > > > > > + if (vmc->acpi_expose_flash) { > > > > > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > > > > > + } > > > > > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]); > > > > > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO], > > > > > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS); > > > > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > > > > > index cd0834ce7faf..5adc9ff799ef 100644 > > > > > --- a/hw/arm/virt.c > > > > > +++ b/hw/arm/virt.c > > > > > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1) > > > > > > > > > > static void virt_machine_5_0_options(MachineClass *mc) > > > > > { > > > > > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc)); > > > > > + > > > > > virt_machine_5_1_options(mc); > > > > > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len); > > > > > mc->numa_mem_supported = true; > > > > > + vmc->acpi_expose_flash = true; > > > > > > > > we usually do not version ACPI tables changes > > > > (unless we have a good reason to do so) > > > > > > Even when the change is to remove the exposure of hardware from the guest? > > > Before this change, if a guest looked, it had a flash, after this change, > > > if a guest looks, it doesn't. > > > > It's up to the relevant maintainers who know what the semantics are. > > FYI ACPI tables only change across a reset though. > > So it's a question of whether guests get confused even if this > > changes after a reboot. > > Yup, but it's still the same "machine", so a user may wonder why it > changed. you can have a different firmware with the same machine type either and it might look differently to guest OS but don't bother versioning FW. APCI tables are also part of FW (but generated by QEMU), so the same usually rule applies. > > Versioning is generally safer, but it's a good idea to document > > the motivation for it. > > > > Well, in this case, we could probably push this change to old machine > types and nobody would notice. If a guest is using ACPI, then it must > be using firmware, and if they're using firmware, then they can't be > using the flash. So the user shouldn't care if it's there or not. The > only justification for the versioning is because "it's safer". If > people feel strongly about avoiding versioning when it's not obviously > necessary, then I can respin without it. From my pov if it doesn't break anything don't version it, since versioning adds complexity which cost time during review, so it would be nicer to reviewers and to future yourself if you can help to keep it as simple as possible. In this particular case I'd drop versioning. > Thanks, > drew > >
On Tue, Jul 14, 2020 at 04:41:41PM +0200, Igor Mammedov wrote: > On Tue, 14 Jul 2020 11:23:25 +0200 > Andrew Jones <drjones@redhat.com> wrote: > > > On Tue, Jul 14, 2020 at 04:57:50AM -0400, Michael S. Tsirkin wrote: > > > On Tue, Jul 14, 2020 at 07:51:09AM +0200, Andrew Jones wrote: > > > > On Mon, Jul 13, 2020 at 10:49:07AM +0200, Igor Mammedov wrote: > > > > > On Mon, 29 Jun 2020 16:09:37 +0200 > > > > > Andrew Jones <drjones@redhat.com> wrote: > > > > > > > > > > > The flash device is exclusively for the host-controlled firmware, so > > > > > > we should not expose it to the OS. Exposing it risks the OS messing > > > > > > with it, which could break firmware runtime services and surprise the > > > > > > OS when all its changes disappear after reboot. > > > > > > > > > > > > As firmware needs the device and uses DT, we leave the device exposed > > > > > > there. It's up to firmware to remove the nodes from DT before sending > > > > > > it on to the OS. However, there's no need to force firmware to remove > > > > > > tables from ACPI (which it doesn't know how to do anyway), so we > > > > > > simply don't add the tables in the first place. But, as we've been > > > > > > adding the tables for quite some time and don't want to change the > > > > > > default hardware exposed to versioned machines, then we only stop > > > > > > exposing the flash device tables for 5.1 and later machine types. > > > > > > > > > > > > Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com> > > > > > > Suggested-by: Laszlo Ersek <lersek@redhat.com> > > > > > > Signed-off-by: Andrew Jones <drjones@redhat.com> > > > > > > --- > > > > > > hw/arm/virt-acpi-build.c | 5 ++++- > > > > > > hw/arm/virt.c | 3 +++ > > > > > > include/hw/arm/virt.h | 1 + > > > > > > 3 files changed, 8 insertions(+), 1 deletion(-) > > > > > > > > > > > > diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c > > > > > > index 1384a2cf2ab4..91f0df7b13a3 100644 > > > > > > --- a/hw/arm/virt-acpi-build.c > > > > > > +++ b/hw/arm/virt-acpi-build.c > > > > > > @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker, > > > > > > static void > > > > > > build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > > > > > > { > > > > > > + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms); > > > > > > Aml *scope, *dsdt; > > > > > > MachineState *ms = MACHINE(vms); > > > > > > const MemMapEntry *memmap = vms->memmap; > > > > > > @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) > > > > > > acpi_dsdt_add_cpus(scope, vms->smp_cpus); > > > > > > acpi_dsdt_add_uart(scope, &memmap[VIRT_UART], > > > > > > (irqmap[VIRT_UART] + ARM_SPI_BASE)); > > > > > > - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > > > > > > + if (vmc->acpi_expose_flash) { > > > > > > + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); > > > > > > + } > > > > > > acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]); > > > > > > acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO], > > > > > > (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS); > > > > > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > > > > > > index cd0834ce7faf..5adc9ff799ef 100644 > > > > > > --- a/hw/arm/virt.c > > > > > > +++ b/hw/arm/virt.c > > > > > > @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1) > > > > > > > > > > > > static void virt_machine_5_0_options(MachineClass *mc) > > > > > > { > > > > > > + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc)); > > > > > > + > > > > > > virt_machine_5_1_options(mc); > > > > > > compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len); > > > > > > mc->numa_mem_supported = true; > > > > > > + vmc->acpi_expose_flash = true; > > > > > > > > > > we usually do not version ACPI tables changes > > > > > (unless we have a good reason to do so) > > > > > > > > Even when the change is to remove the exposure of hardware from the guest? > > > > Before this change, if a guest looked, it had a flash, after this change, > > > > if a guest looks, it doesn't. > > > > > > It's up to the relevant maintainers who know what the semantics are. > > > FYI ACPI tables only change across a reset though. > > > So it's a question of whether guests get confused even if this > > > changes after a reboot. > > > > Yup, but it's still the same "machine", so a user may wonder why it > > changed. > > you can have a different firmware with the same machine type either > and it might look differently to guest OS but don't bother versioning > FW. APCI tables are also part of FW (but generated by QEMU), so the same > usually rule applies. That makes sense. However, while users of real machines agree to update their firmware after determining what will change, or at least expect there could be a change that they'll need to adapt to, users of virtual machines simply reboot, getting new firmware and ACPI tables, and then possibly new surprises. Indeed, they may have opted to use a virtual machine precisely so they could keep the environment stable across updates of the real machine. IOW, since we can maintain a versioned machine, then maybe we should? > > > > Versioning is generally safer, but it's a good idea to document > > > the motivation for it. > > > > > > > Well, in this case, we could probably push this change to old machine > > types and nobody would notice. If a guest is using ACPI, then it must > > be using firmware, and if they're using firmware, then they can't be > > using the flash. So the user shouldn't care if it's there or not. The > > only justification for the versioning is because "it's safer". If > > people feel strongly about avoiding versioning when it's not obviously > > necessary, then I can respin without it. > > From my pov if it doesn't break anything don't version it, I don't see how we can be sure that we won't break anything. Although, in this case, we *probably* won't. > since versioning > adds complexity which cost time during review, so it would be nicer to reviewers > and to future yourself if you can help to keep it as simple as possible. I agree with all of that. > > In this particular case I'd drop versioning. > So it sounds to me like we have some flexibility in our versioned machine maintenance. We can choose to forgo the usual compat code when the risk is deemed low enough. And, if somebody screams, we can always fix it later. I can live with that. I'll go ahead and respin without the versioning. Thanks, drew
On Wed, Jul 15, 2020 at 08:36:48AM +0200, Andrew Jones wrote: > On Tue, Jul 14, 2020 at 04:41:41PM +0200, Igor Mammedov wrote: > > > > In this particular case I'd drop versioning. > > > > So it sounds to me like we have some flexibility in our versioned machine > maintenance. We can choose to forgo the usual compat code when the risk is > deemed low enough. And, if somebody screams, we can always fix it later. > I can live with that. I'll go ahead and respin without the versioning. > Actually this patch was already merged 2c1fb4d5c011 hw/arm/virt-acpi-build: Only expose flash on older machine types and I don't see much value in posting a patch to remove the compat code. Regarding the result of this discussion, my take is that unless the policy is to always or to never use versioning, then I think we should have guidelines documented which we can follow. Would one of the ACPI maintainers like to submit a document with the reasoning for when and when not to use versioning? And also for what's expected of the commit message justification when versioning is necessary? Thanks, drew
Hi Drew, On 07/15/20 08:36, Andrew Jones wrote: > So it sounds to me like we have some flexibility in our versioned machine > maintenance. We can choose to forgo the usual compat code when the risk is > deemed low enough. And, if somebody screams, we can always fix it later. > I can live with that. I'll go ahead and respin without the versioning. In that case, please don't simply remove the acpi_dsdt_add_flash() call from build_dsdt(), because then "git blame" won't be able to help later. Can you please replace the call with a comment instead, similar to the RTC comment from commit 67736a25f865 ("ARM: virt: Don't generate RTC ACPI device when using UEFI", 2016-01-15)? Thanks! Laszlo
On Wed, Jul 15, 2020 at 02:26:19PM +0200, Laszlo Ersek wrote: > Hi Drew, > > On 07/15/20 08:36, Andrew Jones wrote: > > > So it sounds to me like we have some flexibility in our versioned machine > > maintenance. We can choose to forgo the usual compat code when the risk is > > deemed low enough. And, if somebody screams, we can always fix it later. > > I can live with that. I'll go ahead and respin without the versioning. > > In that case, please don't simply remove the acpi_dsdt_add_flash() call > from build_dsdt(), because then "git blame" won't be able to help later. > Can you please replace the call with a comment instead, similar to the > RTC comment from commit 67736a25f865 ("ARM: virt: Don't generate RTC > ACPI device when using UEFI", 2016-01-15)? > In the end I won't be respinning, as this patch is already merged. And, unless Igor twists my arm, then I don't plan to write another patch that removes the compat code. If I did remove it, I'd put a comment in there for git-blame to find. And, in the comment I'd write "Igor said to remove this", because git-blame would otherwise blame me :-) Thanks, drew
diff --git a/hw/arm/virt-acpi-build.c b/hw/arm/virt-acpi-build.c index 1384a2cf2ab4..91f0df7b13a3 100644 --- a/hw/arm/virt-acpi-build.c +++ b/hw/arm/virt-acpi-build.c @@ -749,6 +749,7 @@ static void build_fadt_rev5(GArray *table_data, BIOSLinker *linker, static void build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) { + VirtMachineClass *vmc = VIRT_MACHINE_GET_CLASS(vms); Aml *scope, *dsdt; MachineState *ms = MACHINE(vms); const MemMapEntry *memmap = vms->memmap; @@ -767,7 +768,9 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, VirtMachineState *vms) acpi_dsdt_add_cpus(scope, vms->smp_cpus); acpi_dsdt_add_uart(scope, &memmap[VIRT_UART], (irqmap[VIRT_UART] + ARM_SPI_BASE)); - acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); + if (vmc->acpi_expose_flash) { + acpi_dsdt_add_flash(scope, &memmap[VIRT_FLASH]); + } acpi_dsdt_add_fw_cfg(scope, &memmap[VIRT_FW_CFG]); acpi_dsdt_add_virtio(scope, &memmap[VIRT_MMIO], (irqmap[VIRT_MMIO] + ARM_SPI_BASE), NUM_VIRTIO_TRANSPORTS); diff --git a/hw/arm/virt.c b/hw/arm/virt.c index cd0834ce7faf..5adc9ff799ef 100644 --- a/hw/arm/virt.c +++ b/hw/arm/virt.c @@ -2482,9 +2482,12 @@ DEFINE_VIRT_MACHINE_AS_LATEST(5, 1) static void virt_machine_5_0_options(MachineClass *mc) { + VirtMachineClass *vmc = VIRT_MACHINE_CLASS(OBJECT_CLASS(mc)); + virt_machine_5_1_options(mc); compat_props_add(mc->compat_props, hw_compat_5_0, hw_compat_5_0_len); mc->numa_mem_supported = true; + vmc->acpi_expose_flash = true; } DEFINE_VIRT_MACHINE(5, 0) diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h index 31878ddc7223..c65be5fe0bb6 100644 --- a/include/hw/arm/virt.h +++ b/include/hw/arm/virt.h @@ -119,6 +119,7 @@ typedef struct { bool no_highmem_ecam; bool no_ged; /* Machines < 4.2 has no support for ACPI GED device */ bool kvm_no_adjvtime; + bool acpi_expose_flash; } VirtMachineClass; typedef struct {
The flash device is exclusively for the host-controlled firmware, so we should not expose it to the OS. Exposing it risks the OS messing with it, which could break firmware runtime services and surprise the OS when all its changes disappear after reboot. As firmware needs the device and uses DT, we leave the device exposed there. It's up to firmware to remove the nodes from DT before sending it on to the OS. However, there's no need to force firmware to remove tables from ACPI (which it doesn't know how to do anyway), so we simply don't add the tables in the first place. But, as we've been adding the tables for quite some time and don't want to change the default hardware exposed to versioned machines, then we only stop exposing the flash device tables for 5.1 and later machine types. Suggested-by: Ard Biesheuvel <ard.biesheuvel@arm.com> Suggested-by: Laszlo Ersek <lersek@redhat.com> Signed-off-by: Andrew Jones <drjones@redhat.com> --- hw/arm/virt-acpi-build.c | 5 ++++- hw/arm/virt.c | 3 +++ include/hw/arm/virt.h | 1 + 3 files changed, 8 insertions(+), 1 deletion(-)