[PATCH v3 08/14] KVM: arm64: Propagate EHWPOISON in kvm_s2_fault_pin_pfn()

[Fuad Tabba]

On Tue, 22 Sept 2026 at 15:19, Lorenzo Stoakes (ARM) <ljs at kernel.org> wrote:
>
> Currently kvm_s2_fault_pin_pfn() handles a poisoned page directly by
> sending a SIGBUS signal itself.
>
> This is an odd place to do it, the caller should decide what to do with
> errors, so move the handling to the sole caller, user_mem_abort().
>
> This lays the foundation for stage 2 pre-faulting which, arising from a
> synthetic fault, should not send a signal.
>
> In order to do so, check to see if user_mem_abort()'s caller has set result
> - i.e. whether it wants to be informed about the outcome of the fault
> handling.
>
> If it does, then it is implied that it should handle the -EHWPOISON error
> itself. This is the case for pre-faulting.
>
> Otherwise this is real hardware, so send the signal.
>
> No functional change intended.
>
> Signed-off-by: Lorenzo Stoakes (ARM) <ljs at kernel.org>

Reviewed-by: Fuad Tabba <fuad.tabba at linux.dev>

Cheers,
/fuad

> ---
>  arch/arm64/kvm/mmu.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 221ea069f9bb..2576b967d20e 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -2016,10 +2016,8 @@ static int kvm_s2_fault_pin_pfn(const struct kvm_s2_fault_desc *s2fd,
>                                       kvm_s2_fault_is_write(s2fd) ? FOLL_WRITE : 0,
>                                       &s2vi->map_writable, &s2vi->page);
>         if (unlikely(is_error_noslot_pfn(s2vi->pfn))) {
> -               if (s2vi->pfn == KVM_PFN_ERR_HWPOISON) {
> -                       kvm_send_hwpoison_signal(s2fd->hva, __ffs(s2vi->vma_pagesize));
> -                       return 0;
> -               }
> +               if (s2vi->pfn == KVM_PFN_ERR_HWPOISON)
> +                       return -EHWPOISON;
>                 return -EFAULT;
>         }
>
> @@ -2261,6 +2259,13 @@ static int user_mem_abort(const struct kvm_s2_fault_desc *s2fd,
>          * get block mapping for device MMIO region.
>          */
>         ret = kvm_s2_fault_pin_pfn(s2fd, &s2vi);
> +       if (ret == -EHWPOISON) {
> +               /* If result is specified, let the caller handle this. */
> +               if (result)
> +                       return -EHWPOISON;
> +               kvm_send_hwpoison_signal(s2fd->hva, __ffs(s2vi.vma_pagesize));
> +               return 0;
> +       }
>         if (ret != 1)
>                 return ret;
>
>
> --
> 2.55.0
>