diff mbox series

efi: arm64: Introduce /sys/firmware/efi/memreserve to tell the persistent pages

Message ID 20191125184944.15556-1-msys.mizuma@gmail.com (mailing list archive)
State New, archived
Headers show
Series efi: arm64: Introduce /sys/firmware/efi/memreserve to tell the persistent pages | expand

Commit Message

Masayoshi Mizuma Nov. 25, 2019, 6:49 p.m. UTC 
From: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>

kexec reboot stops in early boot sequence because efi_config_parse_tables()
refers garbage data. We can see the log with memblock=debug kernel option:

  efi:  ACPI 2.0=0x9821790014  PROP=0x8757f5c0  SMBIOS 3.0=0x9820740000  MEMRESERVE=0x9820bfdc58
  memblock_reserve: [0x0000009820bfdc58-0x0000009820bfdc67] efi_config_parse_tables+0x228/0x278
  memblock_reserve: [0x0000000082760000-0x00000000324d07ff] efi_config_parse_tables+0x228/0x278
  memblock_reserve: [0xcc4f84ecc0511670-0x5f6e5214a7fd91f9] efi_config_parse_tables+0x244/0x278
  memblock_reserve: [0xd2fd4144b9af693d-0xad0c1db1086f40a2] efi_config_parse_tables+0x244/0x278
  memblock_reserve: [0x0c719bb159b1fadc-0x5aa6e62a1417ce12] efi_config_parse_tables+0x244/0x278
  ...

That happens because 0x82760000, struct linux_efi_memreserve, is destroyed.
0x82760000 is pointed from efi.mem_reseve, and efi.mem_reserve points the
head page of LPI pending table and LPI property table which are allocated by
gic_reserve_range().

The destroyer is kexec. kexec locates the initrd to the area:

  ]# kexec -d -l /boot/vmlinuz-5.4.0-rc7 /boot/initramfs-5.4.0-rc7.img --reuse-cmdline
  ...
  initrd: base 82290000, size 388dd8ah (59301258)
  ...

From dynamic debug log. initrd is located in segment[1]:
  machine_kexec_prepare:70:
    kexec kimage info:
      type:        0
      start:       85b30680
      head:        0
      nr_segments: 4
        segment[0]: 0000000080480000 - 0000000082290000, 0x1e10000 bytes, 481 pages
        segment[1]: 0000000082290000 - 0000000085b20000, 0x3890000 bytes, 905 pages
        segment[2]: 0000000085b20000 - 0000000085b30000, 0x10000 bytes, 1 pages
        segment[3]: 0000000085b30000 - 0000000085b40000, 0x10000 bytes, 1 pages

kexec searches the memory region to locate initrd through
"System RAM" in /proc/iomem. The pending tables are included in
"System RAM" because they are allocated by alloc_pages(), so kexec
destroys the LPI pending tables.

Introduce /sys/firmware/efi/memreserve to tell the pages pointed by
efi.mem_reserve so that kexec can avoid the area to locate initrd.

Signed-off-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
---
 drivers/firmware/efi/efi.c | 45 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 44 insertions(+), 1 deletion(-)

Comments

Matthias Brugger Nov. 29, 2019, 12:25 p.m. UTC | #1 
On 25/11/2019 19:49, Masayoshi Mizuma wrote:
> From: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
> 
> kexec reboot stops in early boot sequence because efi_config_parse_tables()
> refers garbage data. We can see the log with memblock=debug kernel option:
> 
>   efi:  ACPI 2.0=0x9821790014  PROP=0x8757f5c0  SMBIOS 3.0=0x9820740000  MEMRESERVE=0x9820bfdc58
>   memblock_reserve: [0x0000009820bfdc58-0x0000009820bfdc67] efi_config_parse_tables+0x228/0x278
>   memblock_reserve: [0x0000000082760000-0x00000000324d07ff] efi_config_parse_tables+0x228/0x278
>   memblock_reserve: [0xcc4f84ecc0511670-0x5f6e5214a7fd91f9] efi_config_parse_tables+0x244/0x278
>   memblock_reserve: [0xd2fd4144b9af693d-0xad0c1db1086f40a2] efi_config_parse_tables+0x244/0x278
>   memblock_reserve: [0x0c719bb159b1fadc-0x5aa6e62a1417ce12] efi_config_parse_tables+0x244/0x278
>   ...
> 
> That happens because 0x82760000, struct linux_efi_memreserve, is destroyed.
> 0x82760000 is pointed from efi.mem_reseve, and efi.mem_reserve points the
> head page of LPI pending table and LPI property table which are allocated by
> gic_reserve_range().
> 
> The destroyer is kexec. kexec locates the initrd to the area:
> 
>   ]# kexec -d -l /boot/vmlinuz-5.4.0-rc7 /boot/initramfs-5.4.0-rc7.img --reuse-cmdline
>   ...
>   initrd: base 82290000, size 388dd8ah (59301258)
>   ...
> 
> From dynamic debug log. initrd is located in segment[1]:
>   machine_kexec_prepare:70:
>     kexec kimage info:
>       type:        0
>       start:       85b30680
>       head:        0
>       nr_segments: 4
>         segment[0]: 0000000080480000 - 0000000082290000, 0x1e10000 bytes, 481 pages
>         segment[1]: 0000000082290000 - 0000000085b20000, 0x3890000 bytes, 905 pages
>         segment[2]: 0000000085b20000 - 0000000085b30000, 0x10000 bytes, 1 pages
>         segment[3]: 0000000085b30000 - 0000000085b40000, 0x10000 bytes, 1 pages
> 
> kexec searches the memory region to locate initrd through
> "System RAM" in /proc/iomem. The pending tables are included in
> "System RAM" because they are allocated by alloc_pages(), so kexec
> destroys the LPI pending tables.
> 

Doesn't that mean that you haven't enough memory reserved so that you have to
fallback to allocate it via __get_free_page()?


> Introduce /sys/firmware/efi/memreserve to tell the pages pointed by
> efi.mem_reserve so that kexec can avoid the area to locate initrd.
> 

Doesn't that need a patch for kexec-tools to actually take this into account?

> Signed-off-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
> ---
>  drivers/firmware/efi/efi.c | 45 +++++++++++++++++++++++++++++++++++++-
>  1 file changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> index e98bbf8e5..0aa07cc09 100644
> --- a/drivers/firmware/efi/efi.c
> +++ b/drivers/firmware/efi/efi.c
> @@ -141,6 +141,47 @@ static ssize_t systab_show(struct kobject *kobj,
>  
>  static struct kobj_attribute efi_attr_systab = __ATTR_RO_MODE(systab, 0400);
>  
> +static struct linux_efi_memreserve *efi_memreserve_root __ro_after_init;
> +#ifdef CONFIG_KEXEC
> +static ssize_t memreserve_show(struct kobject *kobj,
> +			   struct kobj_attribute *attr, char *buf)
> +{
> +	struct linux_efi_memreserve *rsv;
> +	phys_addr_t start, end;
> +	unsigned long prsv;
> +	char *str = buf;
> +	int count, i;
> +
> +	if (!kobj || !buf)
> +		return -EINVAL;
> +
> +	if ((efi_memreserve_root == (void *)ULONG_MAX) ||
> +			(!efi_memreserve_root))
> +		return -ENODEV;
> +
> +	for (prsv = efi_memreserve_root->next; prsv; prsv = rsv->next) {
> +		rsv = memremap(prsv, sizeof(*rsv), MEMREMAP_WB);
> +		if (!rsv) {
> +			pr_err("Could not map efi_memreserve\n");
> +			return -ENOMEM;
> +		}
> +		count = atomic_read(&rsv->count);
> +		for (i = 0; i < count; i++) {
> +			start = rsv->entry[i].base;
> +			end = start + rsv->entry[i].size - 1;
> +
> +			str += sprintf(str, "%pa-%pa\n", &start, &end);

What happens if we provide a buf which is too small?

Regards,
Matthias
Masayoshi Mizuma Dec. 3, 2019, 1:28 a.m. UTC | #2 
On Fri, Nov 29, 2019 at 01:25:36PM +0100, Matthias Brugger wrote:
> 
> 
> On 25/11/2019 19:49, Masayoshi Mizuma wrote:
> > From: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
> > 
> > kexec reboot stops in early boot sequence because efi_config_parse_tables()
> > refers garbage data. We can see the log with memblock=debug kernel option:
> > 
> >   efi:  ACPI 2.0=0x9821790014  PROP=0x8757f5c0  SMBIOS 3.0=0x9820740000  MEMRESERVE=0x9820bfdc58
> >   memblock_reserve: [0x0000009820bfdc58-0x0000009820bfdc67] efi_config_parse_tables+0x228/0x278
> >   memblock_reserve: [0x0000000082760000-0x00000000324d07ff] efi_config_parse_tables+0x228/0x278
> >   memblock_reserve: [0xcc4f84ecc0511670-0x5f6e5214a7fd91f9] efi_config_parse_tables+0x244/0x278
> >   memblock_reserve: [0xd2fd4144b9af693d-0xad0c1db1086f40a2] efi_config_parse_tables+0x244/0x278
> >   memblock_reserve: [0x0c719bb159b1fadc-0x5aa6e62a1417ce12] efi_config_parse_tables+0x244/0x278
> >   ...
> > 
> > That happens because 0x82760000, struct linux_efi_memreserve, is destroyed.
> > 0x82760000 is pointed from efi.mem_reseve, and efi.mem_reserve points the
> > head page of LPI pending table and LPI property table which are allocated by
> > gic_reserve_range().
> > 
> > The destroyer is kexec. kexec locates the initrd to the area:
> > 
> >   ]# kexec -d -l /boot/vmlinuz-5.4.0-rc7 /boot/initramfs-5.4.0-rc7.img --reuse-cmdline
> >   ...
> >   initrd: base 82290000, size 388dd8ah (59301258)
> >   ...
> > 
> > From dynamic debug log. initrd is located in segment[1]:
> >   machine_kexec_prepare:70:
> >     kexec kimage info:
> >       type:        0
> >       start:       85b30680
> >       head:        0
> >       nr_segments: 4
> >         segment[0]: 0000000080480000 - 0000000082290000, 0x1e10000 bytes, 481 pages
> >         segment[1]: 0000000082290000 - 0000000085b20000, 0x3890000 bytes, 905 pages
> >         segment[2]: 0000000085b20000 - 0000000085b30000, 0x10000 bytes, 1 pages
> >         segment[3]: 0000000085b30000 - 0000000085b40000, 0x10000 bytes, 1 pages
> > 
> > kexec searches the memory region to locate initrd through
> > "System RAM" in /proc/iomem. The pending tables are included in
> > "System RAM" because they are allocated by alloc_pages(), so kexec
> > destroys the LPI pending tables.
> > 
> 
> Doesn't that mean that you haven't enough memory reserved so that you have to
> fallback to allocate it via __get_free_page()?

That's a not fallback allocation. The pending tables and also property
tables are allocated by alloc_pages() on its_allocate_prop_table() and
its_allocate_pending_table().

> 
> 
> > Introduce /sys/firmware/efi/memreserve to tell the pages pointed by
> > efi.mem_reserve so that kexec can avoid the area to locate initrd.
> > 
> 
> Doesn't that need a patch for kexec-tools to actually take this into account?

Yes, we need a patch for kexec-tools as well. I'm preparing the kexec
patch.

> 
> > Signed-off-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
> > ---
> >  drivers/firmware/efi/efi.c | 45 +++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 44 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
> > index e98bbf8e5..0aa07cc09 100644
> > --- a/drivers/firmware/efi/efi.c
> > +++ b/drivers/firmware/efi/efi.c
> > @@ -141,6 +141,47 @@ static ssize_t systab_show(struct kobject *kobj,
> >  
> >  static struct kobj_attribute efi_attr_systab = __ATTR_RO_MODE(systab, 0400);
> >  
> > +static struct linux_efi_memreserve *efi_memreserve_root __ro_after_init;
> > +#ifdef CONFIG_KEXEC
> > +static ssize_t memreserve_show(struct kobject *kobj,
> > +			   struct kobj_attribute *attr, char *buf)
> > +{
> > +	struct linux_efi_memreserve *rsv;
> > +	phys_addr_t start, end;
> > +	unsigned long prsv;
> > +	char *str = buf;
> > +	int count, i;
> > +
> > +	if (!kobj || !buf)
> > +		return -EINVAL;
> > +
> > +	if ((efi_memreserve_root == (void *)ULONG_MAX) ||
> > +			(!efi_memreserve_root))
> > +		return -ENODEV;
> > +
> > +	for (prsv = efi_memreserve_root->next; prsv; prsv = rsv->next) {
> > +		rsv = memremap(prsv, sizeof(*rsv), MEMREMAP_WB);
> > +		if (!rsv) {
> > +			pr_err("Could not map efi_memreserve\n");
> > +			return -ENOMEM;
> > +		}
> > +		count = atomic_read(&rsv->count);
> > +		for (i = 0; i < count; i++) {
> > +			start = rsv->entry[i].base;
> > +			end = start + rsv->entry[i].size - 1;
> > +
> > +			str += sprintf(str, "%pa-%pa\n", &start, &end);
> 
> What happens if we provide a buf which is too small?

Good point.
The strings may exceed the buffer size (PAGE_SIZE) in case
efi_memreserve_root has a lot of entries.
It might be better to use seq_printf() to show efi_memreserve_root...
I'll move the file from a sysfs entry to a proc entry so that 
efi_memreserve_root can be handled by seq_printf().

Thanks,
Masa
diff mbox series

Patch

diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c
index e98bbf8e5..0aa07cc09 100644
--- a/drivers/firmware/efi/efi.c
+++ b/drivers/firmware/efi/efi.c
@@ -141,6 +141,47 @@  static ssize_t systab_show(struct kobject *kobj,
 
 static struct kobj_attribute efi_attr_systab = __ATTR_RO_MODE(systab, 0400);
 
+static struct linux_efi_memreserve *efi_memreserve_root __ro_after_init;
+#ifdef CONFIG_KEXEC
+static ssize_t memreserve_show(struct kobject *kobj,
+			   struct kobj_attribute *attr, char *buf)
+{
+	struct linux_efi_memreserve *rsv;
+	phys_addr_t start, end;
+	unsigned long prsv;
+	char *str = buf;
+	int count, i;
+
+	if (!kobj || !buf)
+		return -EINVAL;
+
+	if ((efi_memreserve_root == (void *)ULONG_MAX) ||
+			(!efi_memreserve_root))
+		return -ENODEV;
+
+	for (prsv = efi_memreserve_root->next; prsv; prsv = rsv->next) {
+		rsv = memremap(prsv, sizeof(*rsv), MEMREMAP_WB);
+		if (!rsv) {
+			pr_err("Could not map efi_memreserve\n");
+			return -ENOMEM;
+		}
+		count = atomic_read(&rsv->count);
+		for (i = 0; i < count; i++) {
+			start = rsv->entry[i].base;
+			end = start + rsv->entry[i].size - 1;
+
+			str += sprintf(str, "%pa-%pa\n", &start, &end);
+		}
+		memunmap(rsv);
+	}
+
+	return str - buf;
+}
+
+static struct kobj_attribute efi_attr_memreserve =
+			__ATTR_RO_MODE(memreserve, 0444);
+#endif /* CONFIG_KEXEC */
+
 #define EFI_FIELD(var) efi.var
 
 #define EFI_ATTR_SHOW(name) \
@@ -172,6 +213,9 @@  static struct attribute *efi_subsys_attrs[] = {
 	&efi_attr_runtime.attr,
 	&efi_attr_config_table.attr,
 	&efi_attr_fw_platform_size.attr,
+#ifdef CONFIG_KEXEC
+	&efi_attr_memreserve.attr,
+#endif
 	NULL,
 };
 
@@ -955,7 +999,6 @@  int efi_status_to_err(efi_status_t status)
 }
 
 static DEFINE_SPINLOCK(efi_mem_reserve_persistent_lock);
-static struct linux_efi_memreserve *efi_memreserve_root __ro_after_init;
 
 static int __init efi_memreserve_map_root(void)
 {