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Date: Tue, 5 Mar 2024 16:35:34 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 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 2/28/2024 7:20 AM, 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
Nit: members -> a member, since only 'shadow_mmio_value' is added.
> variables. 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.
>
> 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>
Reviewed-by: Binbin Wu <binbin.wu@...ux.intel.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;
> INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
> INIT_LIST_HEAD(&kvm->arch.zapped_obsolete_pages);
> INIT_LIST_HEAD(&kvm->arch.possible_nx_huge_pages);
> diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
> index 02a466de2991..318135daf685 100644
> --- a/arch/x86/kvm/mmu/spte.c
> +++ b/arch/x86/kvm/mmu/spte.c
> @@ -74,10 +74,10 @@ u64 make_mmio_spte(struct kvm_vcpu *vcpu, u64 gfn, unsigned int access)
> u64 spte = generation_mmio_spte_mask(gen);
> u64 gpa = gfn << PAGE_SHIFT;
>
> - WARN_ON_ONCE(!shadow_mmio_value);
> + WARN_ON_ONCE(!vcpu->kvm->arch.shadow_mmio_value);
>
> access &= shadow_mmio_access_mask;
> - spte |= shadow_mmio_value | access;
> + spte |= vcpu->kvm->arch.shadow_mmio_value | access;
> spte |= gpa | shadow_nonpresent_or_rsvd_mask;
> spte |= (gpa & shadow_nonpresent_or_rsvd_mask)
> << SHADOW_NONPRESENT_OR_RSVD_MASK_LEN;
> @@ -411,6 +411,12 @@ void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 mmio_mask, u64 access_mask)
> }
> EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask);
>
> +void kvm_mmu_set_mmio_spte_value(struct kvm *kvm, u64 mmio_value)
> +{
> + kvm->arch.shadow_mmio_value = mmio_value;
> +}
> +EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_value);
> +
> void kvm_mmu_set_me_spte_mask(u64 me_value, u64 me_mask)
> {
> /* shadow_me_value must be a subset of shadow_me_mask */
> diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
> index 26bc95bbc962..1a163aee9ec6 100644
> --- a/arch/x86/kvm/mmu/spte.h
> +++ b/arch/x86/kvm/mmu/spte.h
> @@ -264,9 +264,9 @@ static inline struct kvm_mmu_page *root_to_sp(hpa_t root)
> return spte_to_child_sp(root);
> }
>
> -static inline bool is_mmio_spte(u64 spte)
> +static inline bool is_mmio_spte(struct kvm *kvm, u64 spte)
> {
> - return (spte & shadow_mmio_mask) == shadow_mmio_value &&
> + return (spte & shadow_mmio_mask) == kvm->arch.shadow_mmio_value &&
> likely(enable_mmio_caching);
> }
>
> diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
> index c8a4d92497b4..d15c44a8e123 100644
> --- a/arch/x86/kvm/mmu/tdp_mmu.c
> +++ b/arch/x86/kvm/mmu/tdp_mmu.c
> @@ -495,8 +495,8 @@ static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
> * impact the guest since both the former and current SPTEs
> * are nonpresent.
> */
> - if (WARN_ON_ONCE(!is_mmio_spte(old_spte) &&
> - !is_mmio_spte(new_spte) &&
> + if (WARN_ON_ONCE(!is_mmio_spte(kvm, old_spte) &&
> + !is_mmio_spte(kvm, new_spte) &&
> !is_removed_spte(new_spte)))
> pr_err("Unexpected SPTE change! Nonpresent SPTEs\n"
> "should not be replaced with another,\n"
> @@ -1028,7 +1028,7 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu,
> }
>
> /* If a MMIO SPTE is installed, the MMIO will need to be emulated. */
> - if (unlikely(is_mmio_spte(new_spte))) {
> + if (unlikely(is_mmio_spte(vcpu->kvm, new_spte))) {
> vcpu->stat.pf_mmio_spte_created++;
> trace_mark_mmio_spte(rcu_dereference(iter->sptep), iter->gfn,
> new_spte);
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