linux-kernel - Re: [PATCH 06/21] KVM: x86/mmu: Track shadow MMIO value on a per-VM basis

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Date: Tue, 12 Mar 2024 14:21:43 +1300
From: "Huang, Kai" <kai.huang@...el.com>
To: Paolo Bonzini <pbonzini@...hat.com>, <linux-kernel@...r.kernel.org>,
	<kvm@...r.kernel.org>
CC: <seanjc@...gle.com>, <michael.roth@....com>, <isaku.yamahata@...el.com>,
	<thomas.lendacky@....com>
Subject: Re: [PATCH 06/21] KVM: x86/mmu: Track shadow MMIO value on a per-VM
 basis



On 28/02/2024 12:20 pm, Paolo Bonzini wrote:
> From: Sean Christopherson <seanjc@...gle.com>
> 
> TDX will use a different shadow PTE entry value for MMIO from VMX.  Add > members to kvm_arch and track value for MMIO per-VM instead of global
"members" -> "member".

> variables.  

"variables" -> "variable".

By using the per-VM EPT entry value for MMIO, the existing VMX
> logic is kept working.  Introduce a separate setter function so that guest
> TD can override later.

"guest TD can override " -> "KVM can override for TDX guest".

> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> Message-Id: <229a18434e5d83f45b1fcd7bf1544d79db1becb6.1705965635.git.isaku.yamahata@...el.com>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
>   arch/x86/include/asm/kvm_host.h |  2 ++
>   arch/x86/kvm/mmu.h              |  1 +
>   arch/x86/kvm/mmu/mmu.c          |  8 +++++---
>   arch/x86/kvm/mmu/spte.c         | 10 ++++++++--
>   arch/x86/kvm/mmu/spte.h         |  4 ++--
>   arch/x86/kvm/mmu/tdp_mmu.c      |  6 +++---
>   6 files changed, 21 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 85dc0f7d09e3..a4514c2ef0ec 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1313,6 +1313,8 @@ struct kvm_arch {
>   	 */
>   	spinlock_t mmu_unsync_pages_lock;
>   
> +	u64 shadow_mmio_value;
> +
>   	struct iommu_domain *iommu_domain;
>   	bool iommu_noncoherent;
>   #define __KVM_HAVE_ARCH_NONCOHERENT_DMA
> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
> index 60f21bb4c27b..2c54ba5b0a28 100644
> --- a/arch/x86/kvm/mmu.h
> +++ b/arch/x86/kvm/mmu.h
> @@ -101,6 +101,7 @@ static inline u8 kvm_get_shadow_phys_bits(void)
>   }
>   
>   void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 mmio_mask, u64 access_mask);
> +void kvm_mmu_set_mmio_spte_value(struct kvm *kvm, u64 mmio_value);
>   void kvm_mmu_set_me_spte_mask(u64 me_value, u64 me_mask);
>   void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only);
>   
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index b5baf11359ad..195e46a1f00f 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -2515,7 +2515,7 @@ static int mmu_page_zap_pte(struct kvm *kvm, struct kvm_mmu_page *sp,
>   				return kvm_mmu_prepare_zap_page(kvm, child,
>   								invalid_list);
>   		}
> -	} else if (is_mmio_spte(pte)) {
> +	} else if (is_mmio_spte(kvm, pte)) {
>   		mmu_spte_clear_no_track(spte);
>   	}
>   	return 0;
> @@ -4197,7 +4197,7 @@ static int handle_mmio_page_fault(struct kvm_vcpu *vcpu, u64 addr, bool direct)
>   	if (WARN_ON_ONCE(reserved))
>   		return -EINVAL;
>   
> -	if (is_mmio_spte(spte)) {
> +	if (is_mmio_spte(vcpu->kvm, spte)) {
>   		gfn_t gfn = get_mmio_spte_gfn(spte);
>   		unsigned int access = get_mmio_spte_access(spte);
>   
> @@ -4813,7 +4813,7 @@ EXPORT_SYMBOL_GPL(kvm_mmu_new_pgd);
>   static bool sync_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, gfn_t gfn,
>   			   unsigned int access)
>   {
> -	if (unlikely(is_mmio_spte(*sptep))) {
> +	if (unlikely(is_mmio_spte(vcpu->kvm, *sptep))) {
>   		if (gfn != get_mmio_spte_gfn(*sptep)) {
>   			mmu_spte_clear_no_track(sptep);
>   			return true;
> @@ -6320,6 +6320,8 @@ static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
>   
>   void kvm_mmu_init_vm(struct kvm *kvm)
>   {
> +
> +	kvm->arch.shadow_mmio_value = shadow_mmio_value;

Unintended blank line.

[...]

Acked-by: Kai Huang <kai.huang@...el.com>