[PATCH 1/2] KVM: arm64: Update page shift if stage 2 block mapping not supported

[Gavin Shan]

On 9/1/20 11:33 PM, Alexandru Elisei wrote:
> Commit 196f878a7ac2e (" KVM: arm/arm64: Signal SIGBUS when stage2 discovers
> hwpoison memory") modifies user_mem_abort() to send a SIGBUS signal when
> the fault IPA maps to a hwpoisoned page. Commit 1559b7583ff6 ("KVM:
> arm/arm64: Re-check VMA on detecting a poisoned page") changed
> kvm_send_hwpoison_signal() to use the page shift instead of the VMA because
> at that point the code had already released the mmap lock, which means
> userspace could have modified the VMA.
> 
> If userspace uses hugetlbfs for the VM memory, user_mem_abort() tries to
> map the guest fault IPA using block mappings in stage 2. That is not always
> possible, if, for example, userspace uses dirty page logging for the VM.
> Update the page shift appropriately in those cases when we downgrade the
> stage 2 entry from a block mapping to a page.
> 
> Fixes: 1559b7583ff6 ("KVM: arm/arm64: Re-check VMA on detecting a poisoned page")
> Signed-off-by: Alexandru Elisei <alexandru.elisei at arm.com>
> ---

Reviewed-by: Gavin Shan <gshan at redhat.com>

>   arch/arm64/kvm/mmu.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index ba00bcc0c884..25e7dc52c086 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1877,6 +1877,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>   	    !fault_supports_stage2_huge_mapping(memslot, hva, vma_pagesize)) {
>   		force_pte = true;
>   		vma_pagesize = PAGE_SIZE;
> +		vma_shift = PAGE_SHIFT;
>   	}
>   
>   	/*
>