[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <553e3a0f-156b-e5d2-037b-2d9acaf52329@gmail.com>
Date: Sat, 7 Oct 2023 15:00:41 +0800
From: Like Xu <like.xu.linux@...il.com>
To: Yan Zhao <yan.y.zhao@...el.com>,
Sean Christopherson <seanjc@...gle.com>
Cc: pbonzini@...hat.com, chao.gao@...el.com, kai.huang@...el.com,
robert.hoo.linux@...il.com, yuan.yao@...ux.intel.com,
kvm list <kvm@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 01/12] KVM: x86/mmu: helpers to return if KVM honors
guest MTRRs
On 14/7/2023 2:50 pm, Yan Zhao wrote:
> Added helpers to check if KVM honors guest MTRRs.
> The inner helper __kvm_mmu_honors_guest_mtrrs() is also provided to
> outside callers for the purpose of checking if guest MTRRs were honored
> before stopping non-coherent DMA.
>
> Suggested-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
> ---
> arch/x86/kvm/mmu.h | 7 +++++++
> arch/x86/kvm/mmu/mmu.c | 15 +++++++++++++++
> 2 files changed, 22 insertions(+)
>
> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
> index 92d5a1924fc1..38bd449226f6 100644
> --- a/arch/x86/kvm/mmu.h
> +++ b/arch/x86/kvm/mmu.h
> @@ -235,6 +235,13 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> return -(u32)fault & errcode;
> }
>
> +bool __kvm_mmu_honors_guest_mtrrs(struct kvm *kvm, bool vm_has_noncoherent_dma);
> +
> +static inline bool kvm_mmu_honors_guest_mtrrs(struct kvm *kvm)
> +{
> + return __kvm_mmu_honors_guest_mtrrs(kvm, kvm_arch_has_noncoherent_dma(kvm));
> +}
> +
> void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end);
>
> int kvm_arch_write_log_dirty(struct kvm_vcpu *vcpu);
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 1e5db621241f..b4f89f015c37 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -4516,6 +4516,21 @@ static int kvm_tdp_mmu_page_fault(struct kvm_vcpu *vcpu,
> }
> #endif
>
> +bool __kvm_mmu_honors_guest_mtrrs(struct kvm *kvm, bool vm_has_noncoherent_dma)
According to the motivation provided in the comment, the function will no
longer need to be passed the parameter "struct kvm *kvm" but will rely on
the global parameters (plus vm_has_noncoherent_dma), removing "*kvm" ?
> +{
> + /*
> + * If the TDP is enabled, the host MTRRs are ignored by TDP
> + * (shadow_memtype_mask is non-zero), and the VM has non-coherent DMA
> + * (DMA doesn't snoop CPU caches), KVM's ABI is to honor the memtype
> + * from the guest's MTRRs so that guest accesses to memory that is
> + * DMA'd aren't cached against the guest's wishes.
> + *
> + * Note, KVM may still ultimately ignore guest MTRRs for certain PFNs,
> + * e.g. KVM will force UC memtype for host MMIO.
> + */
> + return vm_has_noncoherent_dma && tdp_enabled && shadow_memtype_mask;
> +}
> +
> int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
> {
> /*
Powered by blists - more mailing lists