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SubjectRe: [PATCH 18/54] KVM: x86/mmu: Move nested NPT reserved bit calculation into MMU proper
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On 22/06/21 19:57, Sean Christopherson wrote:
> Move nested NPT's invocation of reset_shadow_zero_bits_mask() into the
> MMU proper and unexport said function. Aside from dropping an export,
> this is a baby step toward eliminating the call entirely by fixing the
> shadow_root_level confusion.
>
> No functional change intended.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Extra points for adding a comment about why the heck it's there.

Paolo

> ---
> arch/x86/kvm/mmu.h | 3 ---
> arch/x86/kvm/mmu/mmu.c | 11 ++++++++---
> arch/x86/kvm/svm/nested.c | 1 -
> 3 files changed, 8 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
> index 4e926f4935b0..62844bacd13f 100644
> --- a/arch/x86/kvm/mmu.h
> +++ b/arch/x86/kvm/mmu.h
> @@ -68,9 +68,6 @@ static __always_inline u64 rsvd_bits(int s, int e)
> void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 mmio_mask, u64 access_mask);
> void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only);
>
> -void
> -reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context);
> -
> void kvm_init_mmu(struct kvm_vcpu *vcpu);
> void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, unsigned long cr0,
> unsigned long cr4, u64 efer, gpa_t nested_cr3);
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 02c54426e7a2..5a46a87b23b0 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4212,8 +4212,8 @@ static inline u64 reserved_hpa_bits(void)
> * table in guest or amd nested guest, its mmu features completely
> * follow the features in guest.
> */
> -void
> -reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context)
> +static void reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
> + struct kvm_mmu *context)
> {
> /*
> * KVM uses NX when TDP is disabled to handle a variety of scenarios,
> @@ -4247,7 +4247,6 @@ reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context)
> }
>
> }
> -EXPORT_SYMBOL_GPL(reset_shadow_zero_bits_mask);
>
> static inline bool boot_cpu_is_amd(void)
> {
> @@ -4714,6 +4713,12 @@ void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, unsigned long cr0,
> */
> context->shadow_root_level = new_role.base.level;
> }
> +
> + /*
> + * Redo the shadow bits, the reset done by shadow_mmu_init_context()
> + * (above) may use the wrong shadow_root_level.
> + */
> + reset_shadow_zero_bits_mask(vcpu, context);
> }
> EXPORT_SYMBOL_GPL(kvm_init_shadow_npt_mmu);
>
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index 33b2f9337e26..927e545591c3 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -110,7 +110,6 @@ static void nested_svm_init_mmu_context(struct kvm_vcpu *vcpu)
> vcpu->arch.mmu->get_guest_pgd = nested_svm_get_tdp_cr3;
> vcpu->arch.mmu->get_pdptr = nested_svm_get_tdp_pdptr;
> vcpu->arch.mmu->inject_page_fault = nested_svm_inject_npf_exit;
> - reset_shadow_zero_bits_mask(vcpu, vcpu->arch.mmu);
> vcpu->arch.walk_mmu = &vcpu->arch.nested_mmu;
> }
>
>

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