On 20.05.22 09:06, zhenwei pi wrote:
> Origianlly, unpoison_memory() is only used by hwpoison-inject, and
> unpoisons a page which is poisoned by hwpoison-inject too. The kernel PTE
> entry has no change during software poison/unpoison.
>
> On a virtualization platform, it's possible to fix hardware corrupted page
> by hypervisor, typically the hypervisor remaps the error HVA(host virtual
> address). So add a new parameter 'const char *reason' to show the reason
> called by.
>
> Once the corrupted page gets fixed, the guest kernel needs put page to
> buddy. Reuse the page and hit the following issue(Intel Platinum 8260):
> BUG: unable to handle page fault for address: ffff888061646000
> #PF: supervisor write access in kernel mode
> #PF: error_code(0x0002) - not-present page
> PGD 2c01067 P4D 2c01067 PUD 61aaa063 PMD 10089b063 PTE 800fffff9e9b9062
> Oops: 0002 [#1] PREEMPT SMP NOPTI
> CPU: 2 PID: 31106 Comm: stress Kdump: loaded Tainted: G M OE 5.18.0-rc6.bm.1-amd64 #6
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> RIP: 0010:clear_page_erms+0x7/0x10
>
> The kernel PTE entry of the fixed page is still uncorrected, kernel hits
> page fault during prep_new_page. So add 'bool reset_kpte' to get a change
> to fix the PTE entry if the page is fixed by hypervisor.
Why don't we want to do that for the hwpoison case?
>
> Signed-off-by: zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
> ---
> include/linux/mm.h | 2 +-
> mm/hwpoison-inject.c | 2 +-
> mm/memory-failure.c | 26 +++++++++++++++++++-------
> 3 files changed, 21 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 665873c2788c..7ba210e86401 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3191,7 +3191,7 @@ enum mf_flags {
> extern int memory_failure(unsigned long pfn, int flags);
> extern void memory_failure_queue(unsigned long pfn, int flags);
> extern void memory_failure_queue_kick(int cpu);
> -extern int unpoison_memory(unsigned long pfn);
> +extern int unpoison_memory(unsigned long pfn, bool reset_kpte, const char *reason);
> extern int sysctl_memory_failure_early_kill;
> extern int sysctl_memory_failure_recovery;
> extern void shake_page(struct page *p);
> diff --git a/mm/hwpoison-inject.c b/mm/hwpoison-inject.c
> index 5c0cddd81505..0dd17ba98ade 100644
> --- a/mm/hwpoison-inject.c
> +++ b/mm/hwpoison-inject.c
> @@ -57,7 +57,7 @@ static int hwpoison_unpoison(void *data, u64 val)
> if (!capable(CAP_SYS_ADMIN))
> return -EPERM;
>
> - return unpoison_memory(val);
> + return unpoison_memory(val, false, "hwpoison-inject");
s/hwpoison-inject/hwpoison/
or maybe
s/hwpoison-inject/debugfs/
> }
>
> DEFINE_DEBUGFS_ATTRIBUTE(hwpoison_fops, NULL, hwpoison_inject, "%lli\n");
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 95c218bb0a37..a46de3be1dd7 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -2132,21 +2132,26 @@ core_initcall(memory_failure_init);
> /**
> * unpoison_memory - Unpoison a previously poisoned page
> * @pfn: Page number of the to be unpoisoned page
> + * @reset_kpte: Reset the PTE entry for kmap
> + * @reason: The callers tells why unpoisoning the page
> *
> - * Software-unpoison a page that has been poisoned by
> - * memory_failure() earlier.
> + * Unpoison a page that has been poisoned by memory_failure() earlier.
> *
> - * This is only done on the software-level, so it only works
> - * for linux injected failures, not real hardware failures
> + * For linux injected failures, there is no need to reset PTE entry.
> + * It's possible to fix hardware memory failure on a virtualization platform,
> + * once hypervisor fixes the failure, guest needs put page back to buddy and
> + * reset the PTE entry in kernel.
Why can't we do this unconditionally? Just check if the PTE is poisoned,
and if so, reset it.
--
Thanks,
David / dhildenb
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