On Fri, Jul 14, 2023, Yan Zhao wrote:
> Centralize the code to get cache disabled memtype when guest MTRRs are
> honored. If a TDP honors guest MTRRs, it is required to call the provided
> API to get the memtype for CR0.CD=1.
>
> This is the preparation patch for later implementation of fine-grained gfn
> zap for CR0.CD toggles when guest MTRRs are honored.
>
> No functional change intended.
>
> Signed-off-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>
> ---
> arch/x86/kvm/mtrr.c | 16 ++++++++++++++++
> arch/x86/kvm/vmx/vmx.c | 10 +++++-----
> arch/x86/kvm/x86.h | 2 ++
> 3 files changed, 23 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
> index 3ce58734ad22..64c6daa659c8 100644
> --- a/arch/x86/kvm/mtrr.c
> +++ b/arch/x86/kvm/mtrr.c
> @@ -721,3 +721,19 @@ bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
>
> return type == mtrr_default_type(mtrr_state);
> }
> +
> +/*
> + * this routine is supposed to be called when guest mtrrs are honored
> + */
> +void kvm_honors_guest_mtrrs_get_cd_memtype(struct kvm_vcpu *vcpu,
> + u8 *type, bool *ipat)
I really don't like this helper. IMO it's a big net negative for the readability
of vmx_get_mt_mask(). As I said in the previous version, I agree that splitting
logic is generally undesirable, but in this case I strongly believe it's the
lesser evil.
> +{
> + if (kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_CD_NW_CLEARED)) {
> + *type = MTRR_TYPE_WRBACK;
> + *ipat = false;
> + } else {
> + *type = MTRR_TYPE_UNCACHABLE;
> + *ipat = true;
> + }
> +}
> +EXPORT_SYMBOL_GPL(kvm_honors_guest_mtrrs_get_cd_memtype);
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index c1e93678cea4..7fec1ee23b54 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7573,11 +7573,11 @@ static u8 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio)
> return (MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT) | VMX_EPT_IPAT_BIT;
>
> if (kvm_read_cr0_bits(vcpu, X86_CR0_CD)) {
> - if (kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_CD_NW_CLEARED))
> - return MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT;
> - else
> - return (MTRR_TYPE_UNCACHABLE << VMX_EPT_MT_EPTE_SHIFT) |
> - VMX_EPT_IPAT_BIT;
> + bool ipat;
> + u8 cache;
> +
> + kvm_honors_guest_mtrrs_get_cd_memtype(vcpu, &cache, &ipat);
> + return cache << VMX_EPT_MT_EPTE_SHIFT | (ipat ? VMX_EPT_IPAT_BIT : 0);
> }
>
> return kvm_mtrr_get_guest_memory_type(vcpu, gfn) << VMX_EPT_MT_EPTE_SHIFT;
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index 82e3dafc5453..e7733dc4dccc 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -313,6 +313,8 @@ int kvm_mtrr_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data);
> int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
> bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
> int page_num);
> +void kvm_honors_guest_mtrrs_get_cd_memtype(struct kvm_vcpu *vcpu,
> + u8 *type, bool *ipat);
> bool kvm_vector_hashing_enabled(void);
> void kvm_fixup_and_inject_pf_error(struct kvm_vcpu *vcpu, gva_t gva, u16 error_code);
> int x86_decode_emulated_instruction(struct kvm_vcpu *vcpu, int emulation_type,
> --
> 2.17.1
>
