| Message ID | bc85aba60523e0d63e760d5143c5cb57688779d1.camel@infradead.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] hw/acpi: Add vmclock device | expand |
> diff --git a/hw/acpi/vmclock-abi.h b/hw/acpi/vmclock-abi.h > new file mode 100644 > index 0000000000..19cbf85efd > --- /dev/null > +++ b/hw/acpi/vmclock-abi.h > @@ -0,0 +1,186 @@ > +/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) */ > + > +/* > + * This structure provides a vDSO-style clock to VM guests, exposing the > + * relationship (or lack thereof) between the CPU clock (TSC, timebase, arch > + * counter, etc.) and real time. It is designed to address the problem of > + * live migration, which other clock enlightenments do not. > + * > + * When a guest is live migrated, this affects the clock in two ways. > + * > + * First, even between identical hosts the actual frequency of the underlying > + * counter will change within the tolerances of its specification (typically > + * ±50PPM, or 4 seconds a day). This frequency also varies over time on the > + * same host, but can be tracked by NTP as it generally varies slowly. With > + * live migration there is a step change in the frequency, with no warning. > + * > + * Second, there may be a step change in the value of the counter itself, as > + * its accuracy is limited by the precision of the NTP synchronization on the > + * source and destination hosts. > + * > + * So any calibration (NTP, PTP, etc.) which the guest has done on the source > + * host before migration is invalid, and needs to be redone on the new host. > + * > + * In its most basic mode, this structure provides only an indication to the > + * guest that live migration has occurred. This allows the guest to know that > + * its clock is invalid and take remedial action. For applications that need > + * reliable accurate timestamps (e.g. distributed databases), the structure > + * can be mapped all the way to userspace. This allows the application to see > + * directly for itself that the clock is disrupted and take appropriate > + * action, even when using a vDSO-style method to get the time instead of a > + * system call. > + * > + * In its more advanced mode. this structure can also be used to expose the > + * precise relationship of the CPU counter to real time, as calibrated by the > + * host. This means that userspace applications can have accurate time > + * immediately after live migration, rather than having to pause operations > + * and wait for NTP to recover. This mode does, of course, rely on the > + * counter being reliable and consistent across CPUs. > + * > + * Note that this must be true UTC, never with smeared leap seconds. If a > + * guest wishes to construct a smeared clock, it can do so. Presenting a > + * smeared clock through this interface would be problematic because it > + * actually messes with the apparent counter *period*. A linear smearing > + * of 1 ms per second would effectively tweak the counter period by 1000PPM > + * at the start/end of the smearing period, while a sinusoidal smear would > + * basically be impossible to represent. > + * > + * This structure is offered with the intent that it be adopted into the > + * nascent virtio-rtc standard, as a virtio-rtc that does not address the live > + * migration problem seems a little less than fit for purpose. For that > + * reason, certain fields use precisely the same numeric definitions as in > + * the virtio-rtc proposal. The structure can also be exposed through an ACPI > + * device with the CID "VMCLOCK", modelled on the "VMGENID" device except for > + * the fact that it uses a real _CRS to convey the address of the structure > + * (which should be a full page, to allow for mapping directly to userspace). > + */ > + > +#ifndef __VMCLOCK_ABI_H__ > +#define __VMCLOCK_ABI_H__ > + > +#ifdef __KERNEL__ > +#include <linux/types.h> > +#else > +#include <stdint.h> > +#endif > + > +struct vmclock_abi { > + /* CONSTANT FIELDS */ > + uint32_t magic; > +#define VMCLOCK_MAGIC 0x4b4c4356 /* "VCLK" */ > + uint32_t size; /* Size of region containing this structure */ > + uint16_t version; /* 1 */ > + uint8_t counter_id; /* Matches VIRTIO_RTC_COUNTER_xxx except INVALID */ > +#define VMCLOCK_COUNTER_ARM_VCNT 0 > +#define VMCLOCK_COUNTER_X86_TSC 1 > +#define VMCLOCK_COUNTER_INVALID 0xff > + uint8_t time_type; /* Matches VIRTIO_RTC_TYPE_xxx */ > +#define VMCLOCK_TIME_UTC 0 /* Since 1970-01-01 00:00:00z */ > +#define VMCLOCK_TIME_TAI 1 /* Since 1970-01-01 00:00:00z */ > +#define VMCLOCK_TIME_MONOTONIC 2 /* Since undefined epoch */ > +#define VMCLOCK_TIME_INVALID_SMEARED 3 /* Not supported */ > +#define VMCLOCK_TIME_INVALID_MAYBE_SMEARED 4 /* Not supported */ > + > + /* NON-CONSTANT FIELDS PROTECTED BY SEQCOUNT LOCK */ > + uint32_t seq_count; /* Low bit means an update is in progress */ > + /* > + * This field changes to another non-repeating value when the CPU > + * counter is disrupted, for example on live migration. This lets > + * the guest know that it should discard any calibration it has > + * performed of the counter against external sources (NTP/PTP/etc.). > + */ > + uint64_t disruption_marker; > + uint64_t flags; > + /* Indicates that the tai_offset_sec field is valid */ > +#define VMCLOCK_FLAG_TAI_OFFSET_VALID (1 << 0) > + /* > + * Optionally used to notify guests of pending maintenance events. > + * A guest which provides latency-sensitive services may wish to > + * remove itself from service if an event is coming up. Two flags > + * indicate the approximate imminence of the event. > + */ > +#define VMCLOCK_FLAG_DISRUPTION_SOON (1 << 1) /* About a day */ > +#define VMCLOCK_FLAG_DISRUPTION_IMMINENT (1 << 2) /* About an hour */ > +#define VMCLOCK_FLAG_PERIOD_ESTERROR_VALID (1 << 3) > +#define VMCLOCK_FLAG_PERIOD_MAXERROR_VALID (1 << 4) > +#define VMCLOCK_FLAG_TIME_ESTERROR_VALID (1 << 5) > +#define VMCLOCK_FLAG_TIME_MAXERROR_VALID (1 << 6) > + /* > + * If the MONOTONIC flag is set then (other than leap seconds) it is > + * guaranteed that the time calculated according this structure at > + * any given moment shall never appear to be later than the time > + * calculated via the structure at any *later* moment. > + * > + * In particular, a timestamp based on a counter reading taken > + * immediately after setting the low bit of seq_count (and the > + * associated memory barrier), using the previously-valid time and > + * period fields, shall never be later than a timestamp based on > + * a counter reading taken immediately before *clearing* the low > + * bit again after the update, using the about-to-be-valid fields. > + */ > +#define VMCLOCK_FLAG_TIME_MONOTONIC (1 << 7) > + > + uint8_t pad[2]; > + uint8_t clock_status; > +#define VMCLOCK_STATUS_UNKNOWN 0 > +#define VMCLOCK_STATUS_INITIALIZING 1 > +#define VMCLOCK_STATUS_SYNCHRONIZED 2 > +#define VMCLOCK_STATUS_FREERUNNING 3 > +#define VMCLOCK_STATUS_UNRELIABLE 4 > + > + /* > + * The time exposed through this device is never smeared. This field > + * corresponds to the 'subtype' field in virtio-rtc, which indicates > + * the smearing method. However in this case it provides a *hint* to > + * the guest operating system, such that *if* the guest OS wants to > + * provide its users with an alternative clock which does not follow > + * UTC, it may do so in a fashion consistent with the other systems > + * in the nearby environment. > + */ > + uint8_t leap_second_smearing_hint; /* Matches VIRTIO_RTC_SUBTYPE_xxx */ > +#define VMCLOCK_SMEARING_STRICT 0 > +#define VMCLOCK_SMEARING_NOON_LINEAR 1 > +#define VMCLOCK_SMEARING_UTC_SLS 2 > + int16_t tai_offset_sec; > + uint8_t leap_indicator; > + /* > + * This field is based on the VIRTIO_RTC_LEAP_xxx values as defined > + * in the current draft of virtio-rtc, but since smearing cannot be > + * used with the shared memory device, some values are not used. > + * > + * The _POST_POS and _POST_NEG values allow the guest to perform > + * its own smearing during the day or so after a leap second when > + * such smearing may need to continue being applied for a leap > + * second which is now theoretically "historical". > + */ > +#define VMCLOCK_LEAP_NONE 0x00 /* No known nearby leap second */ > +#define VMCLOCK_LEAP_PRE_POS 0x01 /* Positive leap second at EOM */ > +#define VMCLOCK_LEAP_PRE_NEG 0x02 /* Negative leap second at EOM */ > +#define VMCLOCK_LEAP_POS 0x03 /* Set during 23:59:60 second */ > +#define VMCLOCK_LEAP_POST_POS 0x04 > +#define VMCLOCK_LEAP_POST_NEG 0x05 > + > + /* Bit shift for counter_period_frac_sec and its error rate */ > + uint8_t counter_period_shift; > + /* > + * Paired values of counter and UTC at a given point in time. > + */ > + uint64_t counter_value; > + /* > + * Counter period, and error margin of same. The unit of these > + * fields is 1/2^(64 + counter_period_shift) of a second. > + */ > + uint64_t counter_period_frac_sec; > + uint64_t counter_period_esterror_rate_frac_sec; > + uint64_t counter_period_maxerror_rate_frac_sec; > + > + /* > + * Time according to time_type field above. > + */ > + uint64_t time_sec; /* Seconds since time_type epoch */ > + uint64_t time_frac_sec; /* Units of 1/2^64 of a second */ > + uint64_t time_esterror_nanosec; > + uint64_t time_maxerror_nanosec; > +}; > + > +#endif /* __VMCLOCK_ABI_H__ */ We don't want to manually sync headers with Linux. I think Linux abi should live under uapi. When it is there, we can use ./scripts/update-linux-headers.sh machinery to import it.
On 30 July 2024 18:53:18 BST, "Michael S. Tsirkin" <mst@redhat.com> wrote: >We don't want to manually sync headers with Linux. Indeed. I was briefly tempted to fake it, but figured it might get lost if we subsequently do run the script to automatically merge from Linux, before the guest driver is merged there. >I think Linux abi should live under uapi. When it is there, we can use >./scripts/update-linux-headers.sh machinery to import it. This isn't just Linux ABI. It's intended as hypervisor to guest ABI too. In the fullness of time I'm hoping it'll actually be a virtio header. In the meantime, best not to overthink it. It's fine in hw/acpi alongside the device itself for now, I think.
On Tue, Jul 30, 2024 at 08:04:17PM +0100, David Woodhouse wrote: > On 30 July 2024 18:53:18 BST, "Michael S. Tsirkin" <mst@redhat.com> wrote: > >We don't want to manually sync headers with Linux. > > Indeed. I was briefly tempted to fake it, but figured it might get lost if we subsequently do run the script to automatically merge from Linux, before the guest driver is merged there. > > >I think Linux abi should live under uapi. When it is there, we can use > >./scripts/update-linux-headers.sh machinery to import it. > > This isn't just Linux ABI. It's intended as hypervisor to guest ABI too. In the fullness of time I'm hoping it'll actually be a virtio header. In the meantime, best not to overthink it. It's fine in hw/acpi alongside the device itself for now, I think. This is exactly the same as e.g. virtio. We use Linux as a source of truth, it's easier to share with other hypervisors this way. And UAPI and hypervisor ABI requirements wrt stability are mostly the same. It works.
On 30 July 2024 21:45:53 BST, "Michael S. Tsirkin" <mst@redhat.com> wrote: >On Tue, Jul 30, 2024 at 08:04:17PM +0100, David Woodhouse wrote: >> On 30 July 2024 18:53:18 BST, "Michael S. Tsirkin" <mst@redhat.com> wrote: >> >We don't want to manually sync headers with Linux. >> >> Indeed. I was briefly tempted to fake it, but figured it might get lost if we subsequently do run the script to automatically merge from Linux, before the guest driver is merged there. >> >> >I think Linux abi should live under uapi. When it is there, we can use >> >./scripts/update-linux-headers.sh machinery to import it. >> >> This isn't just Linux ABI. It's intended as hypervisor to guest ABI too. In the fullness of time I'm hoping it'll actually be a virtio header. In the meantime, best not to overthink it. It's fine in hw/acpi alongside the device itself for now, I think. > >This is exactly the same as e.g. virtio. We use Linux as a source of truth, it's >easier to share with other hypervisors this way. And UAPI and hypervisor >ABI requirements wrt stability are mostly the same. It works. Perfect. So as and when the header is in its final form in Linux, it can be part of the automated import and we'll use that version. At that point we can drop the one that's sitting alongside the device itself in hw/acpi/.
On Wed, Jul 31, 2024 at 01:23:49AM +0100, David Woodhouse wrote: > On 30 July 2024 21:45:53 BST, "Michael S. Tsirkin" <mst@redhat.com> wrote: > >On Tue, Jul 30, 2024 at 08:04:17PM +0100, David Woodhouse wrote: > >> On 30 July 2024 18:53:18 BST, "Michael S. Tsirkin" <mst@redhat.com> wrote: > >> >We don't want to manually sync headers with Linux. > >> > >> Indeed. I was briefly tempted to fake it, but figured it might get lost if we subsequently do run the script to automatically merge from Linux, before the guest driver is merged there. > >> > >> >I think Linux abi should live under uapi. When it is there, we can use > >> >./scripts/update-linux-headers.sh machinery to import it. > >> > >> This isn't just Linux ABI. It's intended as hypervisor to guest ABI too. In the fullness of time I'm hoping it'll actually be a virtio header. In the meantime, best not to overthink it. It's fine in hw/acpi alongside the device itself for now, I think. > > > >This is exactly the same as e.g. virtio. We use Linux as a source of truth, it's > >easier to share with other hypervisors this way. And UAPI and hypervisor > >ABI requirements wrt stability are mostly the same. It works. > > Perfect. So as and when the header is in its final form in Linux, it can be part of the automated import and we'll use that version. At that point we can drop the one that's sitting alongside the device itself in hw/acpi/. Yes. Maybe add a comment in the temporary header.
On Wed, 2024-07-31 at 17:19 -0400, Michael S. Tsirkin wrote: > > > Perfect. So as and when the header is in its final form in Linux, > > it can be part of the automated import and we'll use that version. > > At that point we can drop the one that's sitting alongside the > > device itself in hw/acpi/. > > Yes. Maybe add a comment in the temporary header. I pondered that, but kind of preferred to have it byte-identical. Admittedly I'm not *planning* to have to change it any more but it's been useful so far that I can just *copy* the file between the Linux and Linux-backport and QEMU repositories.
On Thu, Aug 01, 2024 at 09:49:06AM +0100, David Woodhouse wrote: > On Wed, 2024-07-31 at 17:19 -0400, Michael S. Tsirkin wrote: > > > > > Perfect. So as and when the header is in its final form in Linux, > > > it can be part of the automated import and we'll use that version. > > > At that point we can drop the one that's sitting alongside the > > > device itself in hw/acpi/. > > > > Yes. Maybe add a comment in the temporary header. > > I pondered that, but kind of preferred to have it byte-identical. > > Admittedly I'm not *planning* to have to change it any more but it's > been useful so far that I can just *copy* the file between the Linux > and Linux-backport and QEMU repositories. ok. note machinery we have is clever, it handles __le and such stuff automatically.
On Thu, 2024-08-01 at 05:48 -0400, Michael S. Tsirkin wrote: > On Thu, Aug 01, 2024 at 09:49:06AM +0100, David Woodhouse wrote: > > On Wed, 2024-07-31 at 17:19 -0400, Michael S. Tsirkin wrote: > > > > > > > Perfect. So as and when the header is in its final form in Linux, > > > > it can be part of the automated import and we'll use that version. > > > > At that point we can drop the one that's sitting alongside the > > > > device itself in hw/acpi/. > > > > > > Yes. Maybe add a comment in the temporary header. > > > > I pondered that, but kind of preferred to have it byte-identical. > > > > Admittedly I'm not *planning* to have to change it any more but it's > > been useful so far that I can just *copy* the file between the Linux > > and Linux-backport and QEMU repositories. > > ok. note machinery we have is clever, it handles __le and such stuff > automatically. Sure. But the *temporary* file in hw/acpi isn't using that machinery; it's literally just copied. I can add a comment in the vmclock.c file where we *include* it, noting that it's sitting here in the same directory for now, but in the fullness of time it will be imported from Linux. --- a/hw/acpi/vmclock.c +++ b/hw/acpi/vmclock.c @@ -22,6 +22,7 @@ #include "migration/vmstate.h" #include "sysemu/reset.h" +/* This will come from Linux headers in the end, but we carry our own for now. */ #include "vmclock-abi.h" void vmclock_build_acpi(VmclockState *vms, GArray *table_data,
diff --git a/hw/acpi/Kconfig b/hw/acpi/Kconfig index e07d3204eb..1d4e9f0845 100644 --- a/hw/acpi/Kconfig +++ b/hw/acpi/Kconfig @@ -60,6 +60,11 @@ config ACPI_VMGENID default y depends on PC +config ACPI_VMCLOCK + bool + default y + depends on PC + config ACPI_VIOT bool depends on ACPI diff --git a/hw/acpi/meson.build b/hw/acpi/meson.build index fa5c07db90..77566ae8a8 100644 --- a/hw/acpi/meson.build +++ b/hw/acpi/meson.build @@ -16,6 +16,7 @@ acpi_ss.add(when: 'CONFIG_ACPI_NVDIMM', if_false: files('acpi-nvdimm-stub.c')) acpi_ss.add(when: 'CONFIG_ACPI_PCI', if_true: files('pci.c')) acpi_ss.add(when: 'CONFIG_ACPI_CXL', if_true: files('cxl.c'), if_false: files('cxl-stub.c')) acpi_ss.add(when: 'CONFIG_ACPI_VMGENID', if_true: files('vmgenid.c')) +acpi_ss.add(when: 'CONFIG_ACPI_VMCLOCK', if_true: files('vmclock.c')) acpi_ss.add(when: 'CONFIG_ACPI_HW_REDUCED', if_true: files('generic_event_device.c')) acpi_ss.add(when: 'CONFIG_ACPI_HMAT', if_true: files('hmat.c')) acpi_ss.add(when: 'CONFIG_ACPI_APEI', if_true: files('ghes.c'), if_false: files('ghes-stub.c')) diff --git a/hw/acpi/vmclock-abi.h b/hw/acpi/vmclock-abi.h new file mode 100644 index 0000000000..19cbf85efd --- /dev/null +++ b/hw/acpi/vmclock-abi.h @@ -0,0 +1,186 @@ +/* SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) */ + +/* + * This structure provides a vDSO-style clock to VM guests, exposing the + * relationship (or lack thereof) between the CPU clock (TSC, timebase, arch + * counter, etc.) and real time. It is designed to address the problem of + * live migration, which other clock enlightenments do not. + * + * When a guest is live migrated, this affects the clock in two ways. + * + * First, even between identical hosts the actual frequency of the underlying + * counter will change within the tolerances of its specification (typically + * ±50PPM, or 4 seconds a day). This frequency also varies over time on the + * same host, but can be tracked by NTP as it generally varies slowly. With + * live migration there is a step change in the frequency, with no warning. + * + * Second, there may be a step change in the value of the counter itself, as + * its accuracy is limited by the precision of the NTP synchronization on the + * source and destination hosts. + * + * So any calibration (NTP, PTP, etc.) which the guest has done on the source + * host before migration is invalid, and needs to be redone on the new host. + * + * In its most basic mode, this structure provides only an indication to the + * guest that live migration has occurred. This allows the guest to know that + * its clock is invalid and take remedial action. For applications that need + * reliable accurate timestamps (e.g. distributed databases), the structure + * can be mapped all the way to userspace. This allows the application to see + * directly for itself that the clock is disrupted and take appropriate + * action, even when using a vDSO-style method to get the time instead of a + * system call. + * + * In its more advanced mode. this structure can also be used to expose the + * precise relationship of the CPU counter to real time, as calibrated by the + * host. This means that userspace applications can have accurate time + * immediately after live migration, rather than having to pause operations + * and wait for NTP to recover. This mode does, of course, rely on the + * counter being reliable and consistent across CPUs. + * + * Note that this must be true UTC, never with smeared leap seconds. If a + * guest wishes to construct a smeared clock, it can do so. Presenting a + * smeared clock through this interface would be problematic because it + * actually messes with the apparent counter *period*. A linear smearing + * of 1 ms per second would effectively tweak the counter period by 1000PPM + * at the start/end of the smearing period, while a sinusoidal smear would + * basically be impossible to represent. + * + * This structure is offered with the intent that it be adopted into the + * nascent virtio-rtc standard, as a virtio-rtc that does not address the live + * migration problem seems a little less than fit for purpose. For that + * reason, certain fields use precisely the same numeric definitions as in + * the virtio-rtc proposal. The structure can also be exposed through an ACPI + * device with the CID "VMCLOCK", modelled on the "VMGENID" device except for + * the fact that it uses a real _CRS to convey the address of the structure + * (which should be a full page, to allow for mapping directly to userspace). + */ + +#ifndef __VMCLOCK_ABI_H__ +#define __VMCLOCK_ABI_H__ + +#ifdef __KERNEL__ +#include <linux/types.h> +#else +#include <stdint.h> +#endif + +struct vmclock_abi { + /* CONSTANT FIELDS */ + uint32_t magic; +#define VMCLOCK_MAGIC 0x4b4c4356 /* "VCLK" */ + uint32_t size; /* Size of region containing this structure */ + uint16_t version; /* 1 */ + uint8_t counter_id; /* Matches VIRTIO_RTC_COUNTER_xxx except INVALID */ +#define VMCLOCK_COUNTER_ARM_VCNT 0 +#define VMCLOCK_COUNTER_X86_TSC 1 +#define VMCLOCK_COUNTER_INVALID 0xff + uint8_t time_type; /* Matches VIRTIO_RTC_TYPE_xxx */ +#define VMCLOCK_TIME_UTC 0 /* Since 1970-01-01 00:00:00z */ +#define VMCLOCK_TIME_TAI 1 /* Since 1970-01-01 00:00:00z */ +#define VMCLOCK_TIME_MONOTONIC 2 /* Since undefined epoch */ +#define VMCLOCK_TIME_INVALID_SMEARED 3 /* Not supported */ +#define VMCLOCK_TIME_INVALID_MAYBE_SMEARED 4 /* Not supported */ + + /* NON-CONSTANT FIELDS PROTECTED BY SEQCOUNT LOCK */ + uint32_t seq_count; /* Low bit means an update is in progress */ + /* + * This field changes to another non-repeating value when the CPU + * counter is disrupted, for example on live migration. This lets + * the guest know that it should discard any calibration it has + * performed of the counter against external sources (NTP/PTP/etc.). + */ + uint64_t disruption_marker; + uint64_t flags; + /* Indicates that the tai_offset_sec field is valid */ +#define VMCLOCK_FLAG_TAI_OFFSET_VALID (1 << 0) + /* + * Optionally used to notify guests of pending maintenance events. + * A guest which provides latency-sensitive services may wish to + * remove itself from service if an event is coming up. Two flags + * indicate the approximate imminence of the event. + */ +#define VMCLOCK_FLAG_DISRUPTION_SOON (1 << 1) /* About a day */ +#define VMCLOCK_FLAG_DISRUPTION_IMMINENT (1 << 2) /* About an hour */ +#define VMCLOCK_FLAG_PERIOD_ESTERROR_VALID (1 << 3) +#define VMCLOCK_FLAG_PERIOD_MAXERROR_VALID (1 << 4) +#define VMCLOCK_FLAG_TIME_ESTERROR_VALID (1 << 5) +#define VMCLOCK_FLAG_TIME_MAXERROR_VALID (1 << 6) + /* + * If the MONOTONIC flag is set then (other than leap seconds) it is + * guaranteed that the time calculated according this structure at + * any given moment shall never appear to be later than the time + * calculated via the structure at any *later* moment. + * + * In particular, a timestamp based on a counter reading taken + * immediately after setting the low bit of seq_count (and the + * associated memory barrier), using the previously-valid time and + * period fields, shall never be later than a timestamp based on + * a counter reading taken immediately before *clearing* the low + * bit again after the update, using the about-to-be-valid fields. + */ +#define VMCLOCK_FLAG_TIME_MONOTONIC (1 << 7) + + uint8_t pad[2]; + uint8_t clock_status; +#define VMCLOCK_STATUS_UNKNOWN 0 +#define VMCLOCK_STATUS_INITIALIZING 1 +#define VMCLOCK_STATUS_SYNCHRONIZED 2 +#define VMCLOCK_STATUS_FREERUNNING 3 +#define VMCLOCK_STATUS_UNRELIABLE 4 + + /* + * The time exposed through this device is never smeared. This field + * corresponds to the 'subtype' field in virtio-rtc, which indicates + * the smearing method. However in this case it provides a *hint* to + * the guest operating system, such that *if* the guest OS wants to + * provide its users with an alternative clock which does not follow + * UTC, it may do so in a fashion consistent with the other systems + * in the nearby environment. + */ + uint8_t leap_second_smearing_hint; /* Matches VIRTIO_RTC_SUBTYPE_xxx */ +#define VMCLOCK_SMEARING_STRICT 0 +#define VMCLOCK_SMEARING_NOON_LINEAR 1 +#define VMCLOCK_SMEARING_UTC_SLS 2 + int16_t tai_offset_sec; + uint8_t leap_indicator; + /* + * This field is based on the VIRTIO_RTC_LEAP_xxx values as defined + * in the current draft of virtio-rtc, but since smearing cannot be + * used with the shared memory device, some values are not used. + * + * The _POST_POS and _POST_NEG values allow the guest to perform + * its own smearing during the day or so after a leap second when + * such smearing may need to continue being applied for a leap + * second which is now theoretically "historical". + */ +#define VMCLOCK_LEAP_NONE 0x00 /* No known nearby leap second */ +#define VMCLOCK_LEAP_PRE_POS 0x01 /* Positive leap second at EOM */ +#define VMCLOCK_LEAP_PRE_NEG 0x02 /* Negative leap second at EOM */ +#define VMCLOCK_LEAP_POS 0x03 /* Set during 23:59:60 second */ +#define VMCLOCK_LEAP_POST_POS 0x04 +#define VMCLOCK_LEAP_POST_NEG 0x05 + + /* Bit shift for counter_period_frac_sec and its error rate */ + uint8_t counter_period_shift; + /* + * Paired values of counter and UTC at a given point in time. + */ + uint64_t counter_value; + /* + * Counter period, and error margin of same. The unit of these + * fields is 1/2^(64 + counter_period_shift) of a second. + */ + uint64_t counter_period_frac_sec; + uint64_t counter_period_esterror_rate_frac_sec; + uint64_t counter_period_maxerror_rate_frac_sec; + + /* + * Time according to time_type field above. + */ + uint64_t time_sec; /* Seconds since time_type epoch */ + uint64_t time_frac_sec; /* Units of 1/2^64 of a second */ + uint64_t time_esterror_nanosec; + uint64_t time_maxerror_nanosec; +}; + +#endif /* __VMCLOCK_ABI_H__ */ diff --git a/hw/acpi/vmclock.c b/hw/acpi/vmclock.c new file mode 100644 index 0000000000..ca89cb3106 --- /dev/null +++ b/hw/acpi/vmclock.c @@ -0,0 +1,183 @@ +/* + * Virtual Machine Clock Device + * + * Copyright © 2024 Amazon.com, Inc. or its affiliates. All Rights Reserved. + * + * Authors: David Woodhouse <dwmw2@infradead.org> + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#include "qemu/osdep.h" +#include "qapi/error.h" +#include "qemu/module.h" +#include "hw/i386/e820_memory_layout.h" +#include "hw/acpi/acpi.h" +#include "hw/acpi/aml-build.h" +#include "hw/acpi/vmclock.h" +#include "hw/nvram/fw_cfg.h" +#include "hw/qdev-properties.h" +#include "hw/qdev-properties-system.h" +#include "migration/vmstate.h" +#include "sysemu/reset.h" + +#include "vmclock-abi.h" + +void vmclock_build_acpi(VmclockState *vms, GArray *table_data, + BIOSLinker *linker, const char *oem_id) +{ + Aml *ssdt, *dev, *scope, *method, *addr, *crs; + AcpiTable table = { .sig = "SSDT", .rev = 1, + .oem_id = oem_id, .oem_table_id = "VMCLOCK" }; + + /* Put VMCLOCK into a separate SSDT table */ + acpi_table_begin(&table, table_data); + ssdt = init_aml_allocator(); + + scope = aml_scope("\\_SB"); + dev = aml_device("VCLK"); + aml_append(dev, aml_name_decl("_HID", aml_string("AMZNC10C"))); + aml_append(dev, aml_name_decl("_CID", aml_string("VMCLOCK"))); + aml_append(dev, aml_name_decl("_DDN", aml_string("VMCLOCK"))); + + /* Simple status method */ + method = aml_method("_STA", 0, AML_NOTSERIALIZED); + addr = aml_local(0); + aml_append(method, aml_store(aml_int(0xf), addr)); + aml_append(method, aml_return(addr)); + aml_append(dev, method); + + crs = aml_resource_template(); + aml_append(crs, aml_qword_memory(AML_POS_DECODE, + AML_MIN_FIXED, AML_MAX_FIXED, + AML_CACHEABLE, AML_READ_ONLY, + 0xffffffffffffffffULL, + vms->physaddr, + vms->physaddr + VMCLOCK_SIZE - 1, + 0, VMCLOCK_SIZE)); + aml_append(dev, aml_name_decl("_CRS", crs)); + aml_append(scope, dev); + aml_append(ssdt, scope); + + g_array_append_vals(table_data, ssdt->buf->data, ssdt->buf->len); + acpi_table_end(linker, &table); + free_aml_allocator(); +} + +static void vmclock_update_guest(VmclockState *vms) +{ + uint64_t disruption_marker; + uint32_t seq_count; + + if (!vms->clk) { + return; + } + + seq_count = le32_to_cpu(vms->clk->seq_count) | 1; + vms->clk->seq_count = cpu_to_le32(seq_count); + smp_wmb(); + + disruption_marker = le64_to_cpu(vms->clk->disruption_marker); + disruption_marker++; + vms->clk->disruption_marker = cpu_to_le64(disruption_marker); + + smp_wmb(); + vms->clk->seq_count = cpu_to_le32(seq_count + 1); +} + +/* After restoring an image, we need to update the guest memory and notify + * it of a potential change to VM Generation ID + */ +static int vmclock_post_load(void *opaque, int version_id) +{ + VmclockState *vms = opaque; + vmclock_update_guest(vms); + return 0; +} + +static const VMStateDescription vmstate_vmclock = { + .name = "vmclock", + .version_id = 1, + .minimum_version_id = 1, + .post_load = vmclock_post_load, + .fields = (const VMStateField[]) { + VMSTATE_UINT64(physaddr, VmclockState), + VMSTATE_END_OF_LIST() + }, +}; + +static void vmclock_handle_reset(void *opaque) +{ + VmclockState *vms = VMCLOCK(opaque); + + if (!memory_region_is_mapped(&vms->clk_page)) { + memory_region_add_subregion_overlap(get_system_memory(), + vms->physaddr, + &vms->clk_page, 0); + } +} + +static void vmclock_realize(DeviceState *dev, Error **errp) +{ + VmclockState *vms = VMCLOCK(dev); + + /* Given that this function is executing, there is at least one VMCLOCK + * device. Check if there are several. + */ + if (!find_vmclock_dev()) { + error_setg(errp, "at most one %s device is permitted", TYPE_VMCLOCK); + return; + } + + vms->physaddr = VMCLOCK_ADDR; + + e820_add_entry(vms->physaddr, VMCLOCK_SIZE, E820_RESERVED); + + memory_region_init_ram(&vms->clk_page, OBJECT(dev), "vmclock_page", + VMCLOCK_SIZE, &error_abort); + memory_region_set_enabled(&vms->clk_page, true); + vms->clk = memory_region_get_ram_ptr(&vms->clk_page); + memset(vms->clk, 0, VMCLOCK_SIZE); + + vms->clk->magic = cpu_to_le32(VMCLOCK_MAGIC); + vms->clk->size = cpu_to_le16(VMCLOCK_SIZE); + vms->clk->version = cpu_to_le16(1); + + /* These are all zero and thus default, but be explicit */ + vms->clk->clock_status = VMCLOCK_STATUS_UNKNOWN; + vms->clk->counter_id = VMCLOCK_COUNTER_INVALID; + + qemu_register_reset(vmclock_handle_reset, vms); + + vmclock_update_guest(vms); +} + +static Property vmclock_device_properties[] = { + DEFINE_PROP_END_OF_LIST(), +}; + +static void vmclock_device_class_init(ObjectClass *klass, void *data) +{ + DeviceClass *dc = DEVICE_CLASS(klass); + + dc->vmsd = &vmstate_vmclock; + dc->realize = vmclock_realize; + device_class_set_props(dc, vmclock_device_properties); + dc->hotpluggable = false; + set_bit(DEVICE_CATEGORY_MISC, dc->categories); +} + +static const TypeInfo vmclock_device_info = { + .name = TYPE_VMCLOCK, + .parent = TYPE_DEVICE, + .instance_size = sizeof(VmclockState), + .class_init = vmclock_device_class_init, +}; + +static void vmclock_register_types(void) +{ + type_register_static(&vmclock_device_info); +} + +type_init(vmclock_register_types) diff --git a/hw/i386/Kconfig b/hw/i386/Kconfig index f4a33b6c08..86b00bb94f 100644 --- a/hw/i386/Kconfig +++ b/hw/i386/Kconfig @@ -43,6 +43,7 @@ config PC select SERIAL_ISA select ACPI_PCI select ACPI_VMGENID + select ACPI_VMCLOCK select VIRTIO_PMEM_SUPPORTED select VIRTIO_MEM_SUPPORTED select HV_BALLOON_SUPPORTED diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c index 5d4bd2b710..e4dfad148e 100644 --- a/hw/i386/acpi-build.c +++ b/hw/i386/acpi-build.c @@ -43,6 +43,7 @@ #include "sysemu/tpm.h" #include "hw/acpi/tpm.h" #include "hw/acpi/vmgenid.h" +#include "hw/acpi/vmclock.h" #include "hw/acpi/erst.h" #include "hw/acpi/piix4.h" #include "sysemu/tpm_backend.h" @@ -2505,7 +2506,7 @@ void acpi_build(AcpiBuildTables *tables, MachineState *machine) uint8_t *u; GArray *tables_blob = tables->table_data; AcpiSlicOem slic_oem = { .id = NULL, .table_id = NULL }; - Object *vmgenid_dev; + Object *vmgenid_dev, *vmclock_dev; char *oem_id; char *oem_table_id; @@ -2578,6 +2579,13 @@ void acpi_build(AcpiBuildTables *tables, MachineState *machine) tables->vmgenid, tables->linker, x86ms->oem_id); } + vmclock_dev = find_vmclock_dev(); + if (vmclock_dev) { + acpi_add_table(table_offsets, tables_blob); + vmclock_build_acpi(VMCLOCK(vmclock_dev), tables_blob, tables->linker, + x86ms->oem_id); + } + if (misc.has_hpet) { acpi_add_table(table_offsets, tables_blob); build_hpet(tables_blob, tables->linker, x86ms->oem_id, diff --git a/include/hw/acpi/vmclock.h b/include/hw/acpi/vmclock.h new file mode 100644 index 0000000000..5605605812 --- /dev/null +++ b/include/hw/acpi/vmclock.h @@ -0,0 +1,34 @@ +#ifndef ACPI_VMCLOCK_H +#define ACPI_VMCLOCK_H + +#include "hw/acpi/bios-linker-loader.h" +#include "hw/qdev-core.h" +#include "qemu/uuid.h" +#include "qom/object.h" + +#define TYPE_VMCLOCK "vmclock" + +#define VMCLOCK_ADDR 0xfeffb000 +#define VMCLOCK_SIZE 0x1000 + +OBJECT_DECLARE_SIMPLE_TYPE(VmclockState, VMCLOCK) + +struct vmclock_abi; + +struct VmclockState { + DeviceState parent_obj; + MemoryRegion clk_page; + uint64_t physaddr; + struct vmclock_abi *clk; +}; + +/* returns NULL unless there is exactly one device */ +static inline Object *find_vmclock_dev(void) +{ + return object_resolve_path_type("", TYPE_VMCLOCK, NULL); +} + +void vmclock_build_acpi(VmclockState *vms, GArray *table_data, + BIOSLinker *linker, const char *oem_id); + +#endif