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SubjectRe: [PATCH v4 03/14] X86/nVMX: Update the PML table without mapping and unmapping the page
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On 03.12.18 10:30, KarimAllah Ahmed wrote:
> Update the PML table without mapping and unmapping the page. This also
> avoids using kvm_vcpu_gpa_to_page(..) which assumes that there is a "struct
> page" for guest memory.
>
> Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
> ---
> v1 -> v2:
> - Use kvm_write_guest_page instead of kvm_write_guest (pbonzini)
> - Do not use pointer arithmetic for pml_address (pbonzini)
> ---
> arch/x86/kvm/vmx.c | 14 +++++---------
> 1 file changed, 5 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 75817cb..6d6dfa9 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -14427,9 +14427,7 @@ static int vmx_write_pml_buffer(struct kvm_vcpu *vcpu)
> {
> struct vmcs12 *vmcs12;
> struct vcpu_vmx *vmx = to_vmx(vcpu);
> - gpa_t gpa;
> - struct page *page = NULL;
> - u64 *pml_address;
> + gpa_t gpa, dst;
>
> if (is_guest_mode(vcpu)) {
> WARN_ON_ONCE(vmx->nested.pml_full);
> @@ -14449,15 +14447,13 @@ static int vmx_write_pml_buffer(struct kvm_vcpu *vcpu)
> }
>
> gpa = vmcs_read64(GUEST_PHYSICAL_ADDRESS) & ~0xFFFull;
> + dst = vmcs12->pml_address + sizeof(u64) * vmcs12->guest_pml_index;
>
> - page = kvm_vcpu_gpa_to_page(vcpu, vmcs12->pml_address);
> - if (is_error_page(page))
> + if (kvm_write_guest_page(vcpu->kvm, gpa_to_gfn(dst), &gpa,
> + offset_in_page(dst), sizeof(gpa)))
> return 0;
>
> - pml_address = kmap(page);
> - pml_address[vmcs12->guest_pml_index--] = gpa;
> - kunmap(page);
> - kvm_release_page_clean(page);

So we've written to the page but released it as clean ... shouldn't that
have been kvm_release_page_dirty?

... also, shouldn't there have been a mark_page_dirty() ?
(to mark it dirty for migration?)

Your patch certainly fixes both conditions (if it was in fact broken).
In that case, we should maybe add that to the cover letter.

Reviewed-by: David Hildenbrand <david@redhat.com>

> + vmcs12->guest_pml_index--;
> }
>
> return 0;
>


--

Thanks,

David / dhildenb

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