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SubjectRe: [PATCH] KVM: x86/mmu: Avoid mixing gpa_t with gfn_t in walk_addr_generic()
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On 22/06/20 17:14, Vitaly Kuznetsov wrote:
> translate_gpa() returns a GPA, assigning it to 'real_gfn' seems obviously
> wrong. There is no real issue because both 'gpa_t' and 'gfn_t' are u64 and
> we don't use the value in 'real_gfn' as a GFN, we do
>
> real_gfn = gpa_to_gfn(real_gfn);
>
> instead. 'If you see a "buffalo" sign on an elephant's cage, do not trust
> your eyes', but let's fix it for good.
>
> No functional change intended.
>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
> arch/x86/kvm/mmu/paging_tmpl.h | 9 +++------
> 1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
> index a6d484ea110b..58234bfaca07 100644
> --- a/arch/x86/kvm/mmu/paging_tmpl.h
> +++ b/arch/x86/kvm/mmu/paging_tmpl.h
> @@ -360,7 +360,6 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
> ++walker->level;
>
> do {
> - gfn_t real_gfn;
> unsigned long host_addr;
>
> pt_access = pte_access;
> @@ -375,7 +374,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
> walker->table_gfn[walker->level - 1] = table_gfn;
> walker->pte_gpa[walker->level - 1] = pte_gpa;
>
> - real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn),
> + real_gpa = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn),
> nested_access,
> &walker->fault);
>
> @@ -389,12 +388,10 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
> * information to fix the exit_qualification or exit_info_1
> * fields.
> */
> - if (unlikely(real_gfn == UNMAPPED_GVA))
> + if (unlikely(real_gpa == UNMAPPED_GVA))
> return 0;
>
> - real_gfn = gpa_to_gfn(real_gfn);
> -
> - host_addr = kvm_vcpu_gfn_to_hva_prot(vcpu, real_gfn,
> + host_addr = kvm_vcpu_gfn_to_hva_prot(vcpu, gpa_to_gfn(real_gpa),
> &walker->pte_writable[walker->level - 1]);
> if (unlikely(kvm_is_error_hva(host_addr)))
> goto error;
>

Queued, thanks.

Paolo

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