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From:   isaku.yamahata@intel.com
To:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     isaku.yamahata@intel.com, isaku.yamahata@gmail.com,
        Paolo Bonzini <pbonzini@redhat.com>, erdemaktas@google.com,
        Sean Christopherson <seanjc@google.com>,
        Sagi Shahar <sagis@google.com>
Subject: [PATCH v8 033/103] KVM: x86/mmu: Track shadow MMIO value/mask on a per-VM basis
Date:   Sun,  7 Aug 2022 15:01:18 -0700
Message-Id: <c734925961e4c0b93125c4af81e887df531305c7.1659854790.git.isaku.yamahata@intel.com>
In-Reply-To: <cover.1659854790.git.isaku.yamahata@intel.com>
References: <cover.1659854790.git.isaku.yamahata@intel.com>
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From: Sean Christopherson <sean.j.christopherson@intel.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
variables.  By using the per-VM EPT entry value for MMIO, the existing VMX
logic is kept working.  To untangle the logic to initialize
shadow_mmio_access_mask, introduce a separate setter function.

At the same time, disallow MMIO emulation path for protected guest because
VMM can't parse instructions in protected guest memory.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
---
 arch/x86/include/asm/kvm_host.h |  4 +++
 arch/x86/kvm/mmu.h              |  3 ++-
 arch/x86/kvm/mmu/mmu.c          |  9 ++++---
 arch/x86/kvm/mmu/spte.c         | 45 +++++++++------------------------
 arch/x86/kvm/mmu/spte.h         | 10 +++-----
 arch/x86/kvm/mmu/tdp_mmu.c      | 13 +++++++---
 arch/x86/kvm/svm/svm.c          | 11 +++++---
 arch/x86/kvm/vmx/vmx.c          | 26 +++++++++++++++++++
 arch/x86/kvm/vmx/x86_ops.h      |  1 +
 9 files changed, 70 insertions(+), 52 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6787d5214fd8..3c4051d4512b 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1157,6 +1157,10 @@ struct kvm_arch {
 	 */
 	spinlock_t mmu_unsync_pages_lock;
 
+	bool enable_mmio_caching;
+	u64 shadow_mmio_value;
+	u64 shadow_mmio_mask;
+
 	struct list_head assigned_dev_head;
 	struct iommu_domain *iommu_domain;
 	bool iommu_noncoherent;
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index df9f79ee07d4..dea9f2ed0177 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -98,7 +98,8 @@ static inline u8 kvm_get_shadow_phys_bits(void)
 	return boot_cpu_data.x86_phys_bits;
 }
 
-void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 mmio_mask, u64 access_mask);
+void kvm_mmu_set_mmio_spte_mask(struct kvm *kvm, u64 mmio_value, u64 mmio_mask);
+void kvm_mmu_set_mmio_access_mask(u64 mmio_access_mask);
 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 216708a433e7..88fc2218fcc3 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2418,7 +2418,7 @@ 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;
@@ -3222,7 +3222,8 @@ static int handle_abnormal_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fau
 		 * and only if L1's MAXPHYADDR is inaccurate with respect to
 		 * the hardware's).
 		 */
-		if (unlikely(!enable_mmio_caching) ||
+		if (unlikely(!vcpu->kvm->arch.enable_mmio_caching &&
+			     !kvm_gfn_shared_mask(vcpu->kvm)) ||
 		    unlikely(fault->gfn > kvm_mmu_max_gfn()))
 			return RET_PF_EMULATE;
 	}
@@ -4074,7 +4075,7 @@ static int handle_mmio_page_fault(struct kvm_vcpu *vcpu, u64 addr, bool direct)
 	if (WARN_ON(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);
 
@@ -4529,7 +4530,7 @@ static unsigned long get_cr3(struct kvm_vcpu *vcpu)
 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;
diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
index 24cba35570ae..3ad16124eeeb 100644
--- a/arch/x86/kvm/mmu/spte.c
+++ b/arch/x86/kvm/mmu/spte.c
@@ -29,8 +29,6 @@ u64 __read_mostly shadow_x_mask; /* mutual exclusive with nx_mask */
 u64 __read_mostly shadow_user_mask;
 u64 __read_mostly shadow_accessed_mask;
 u64 __read_mostly shadow_dirty_mask;
-u64 __read_mostly shadow_mmio_value;
-u64 __read_mostly shadow_mmio_mask;
 u64 __read_mostly shadow_mmio_access_mask;
 u64 __read_mostly shadow_present_mask;
 u64 __read_mostly shadow_memtype_mask;
@@ -60,10 +58,10 @@ 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;
@@ -335,9 +333,8 @@ u64 mark_spte_for_access_track(u64 spte)
 	return spte;
 }
 
-void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 mmio_mask, u64 access_mask)
+void kvm_mmu_set_mmio_spte_mask(struct kvm *kvm, u64 mmio_value, u64 mmio_mask)
 {
-	BUG_ON((u64)(unsigned)access_mask != access_mask);
 	WARN_ON(mmio_value & shadow_nonpresent_or_rsvd_lower_gfn_mask);
 
 	if (!enable_mmio_caching)
@@ -364,12 +361,9 @@ void kvm_mmu_set_mmio_spte_mask(u64 mmio_value, u64 mmio_mask, u64 access_mask)
 	    WARN_ON(mmio_value && (REMOVED_SPTE & mmio_mask) == mmio_value))
 		mmio_value = 0;
 
-	if (!mmio_value)
-		enable_mmio_caching = false;
-
-	shadow_mmio_value = mmio_value;
-	shadow_mmio_mask  = mmio_mask;
-	shadow_mmio_access_mask = access_mask;
+	kvm->arch.enable_mmio_caching = !!mmio_value;
+	kvm->arch.shadow_mmio_value = mmio_value;
+	kvm->arch.shadow_mmio_mask = mmio_mask;
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask);
 
@@ -404,20 +398,12 @@ void kvm_mmu_set_ept_masks(bool has_ad_bits, bool has_exec_only)
 	shadow_acc_track_mask	= VMX_EPT_RWX_MASK;
 	shadow_host_writable_mask = EPT_SPTE_HOST_WRITABLE;
 	shadow_mmu_writable_mask  = EPT_SPTE_MMU_WRITABLE;
-
-	/*
-	 * EPT Misconfigurations are generated if the value of bits 2:0
-	 * of an EPT paging-structure entry is 110b (write/execute).
-	 */
-	kvm_mmu_set_mmio_spte_mask(VMX_EPT_MISCONFIG_WX_VALUE,
-				   VMX_EPT_RWX_MASK, 0);
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_set_ept_masks);
 
 void kvm_mmu_reset_all_pte_masks(void)
 {
 	u8 low_phys_bits;
-	u64 mask;
 
 	shadow_phys_bits = kvm_get_shadow_phys_bits();
 
@@ -464,18 +450,11 @@ void kvm_mmu_reset_all_pte_masks(void)
 
 	shadow_host_writable_mask = DEFAULT_SPTE_HOST_WRITABLE;
 	shadow_mmu_writable_mask  = DEFAULT_SPTE_MMU_WRITABLE;
+}
 
-	/*
-	 * Set a reserved PA bit in MMIO SPTEs to generate page faults with
-	 * PFEC.RSVD=1 on MMIO accesses.  64-bit PTEs (PAE, x86-64, and EPT
-	 * paging) support a maximum of 52 bits of PA, i.e. if the CPU supports
-	 * 52-bit physical addresses then there are no reserved PA bits in the
-	 * PTEs and so the reserved PA approach must be disabled.
-	 */
-	if (shadow_phys_bits < 52)
-		mask = BIT_ULL(51) | PT_PRESENT_MASK;
-	else
-		mask = 0;
-
-	kvm_mmu_set_mmio_spte_mask(mask, mask, ACC_WRITE_MASK | ACC_USER_MASK);
+void kvm_mmu_set_mmio_access_mask(u64 mmio_access_mask)
+{
+	BUG_ON((u64)(unsigned)mmio_access_mask != mmio_access_mask);
+	shadow_mmio_access_mask = mmio_access_mask;
 }
+EXPORT_SYMBOL(kvm_mmu_set_mmio_access_mask);
diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
index 30f456e59e58..824ab5490d5c 100644
--- a/arch/x86/kvm/mmu/spte.h
+++ b/arch/x86/kvm/mmu/spte.h
@@ -5,8 +5,6 @@
 
 #include "mmu_internal.h"
 
-extern bool __read_mostly enable_mmio_caching;
-
 /*
  * A MMU present SPTE is backed by actual memory and may or may not be present
  * in hardware.  E.g. MMIO SPTEs are not considered present.  Use bit 11, as it
@@ -156,8 +154,6 @@ extern u64 __read_mostly shadow_x_mask; /* mutual exclusive with nx_mask */
 extern u64 __read_mostly shadow_user_mask;
 extern u64 __read_mostly shadow_accessed_mask;
 extern u64 __read_mostly shadow_dirty_mask;
-extern u64 __read_mostly shadow_mmio_value;
-extern u64 __read_mostly shadow_mmio_mask;
 extern u64 __read_mostly shadow_mmio_access_mask;
 extern u64 __read_mostly shadow_present_mask;
 extern u64 __read_mostly shadow_memtype_mask;
@@ -231,10 +227,10 @@ static inline int spte_index(u64 *sptep)
  */
 extern u64 __read_mostly shadow_nonpresent_or_rsvd_lower_gfn_mask;
 
-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 &&
-	       likely(enable_mmio_caching);
+	return (spte & kvm->arch.shadow_mmio_mask) == kvm->arch.shadow_mmio_value &&
+		likely(kvm->arch.enable_mmio_caching || kvm_gfn_shared_mask(kvm));
 }
 
 static inline bool is_shadow_present_pte(u64 pte)
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index af510dd31ebc..8bc3a8d1803e 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -569,8 +569,8 @@ 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(!is_mmio_spte(old_spte) &&
-			    !is_mmio_spte(new_spte) &&
+		if (WARN_ON(!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"
@@ -1094,7 +1094,7 @@ 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);
@@ -1863,6 +1863,13 @@ int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes,
 
 	*root_level = vcpu->arch.mmu->root_role.level;
 
+	/*
+	 * mmio page fault isn't supported for protected guest because
+	 * instructions in protected guest memory can't be parsed by VMM.
+	 */
+	if (WARN_ON(kvm_gfn_shared_mask(vcpu->kvm)))
+		return leaf;
+
 	tdp_mmu_for_each_pte(iter, mmu, gfn, gfn + 1) {
 		leaf = iter.level;
 		sptes[leaf] = iter.old_spte;
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 8aa3c95e8b6e..07829be93c93 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -229,6 +229,7 @@ module_param(dump_invalid_vmcb, bool, 0644);
 bool intercept_smi = true;
 module_param(intercept_smi, bool, 0444);
 
+static u64 __read_mostly svm_shadow_mmio_mask;
 
 static bool svm_gp_erratum_intercept = true;
 
@@ -4729,6 +4730,9 @@ static bool svm_is_vm_type_supported(unsigned long type)
 
 static int svm_vm_init(struct kvm *kvm)
 {
+	kvm_mmu_set_mmio_spte_mask(kvm, svm_shadow_mmio_mask,
+				   svm_shadow_mmio_mask);
+
 	if (!pause_filter_count || !pause_filter_thresh)
 		kvm->arch.pause_in_guest = true;
 
@@ -4878,7 +4882,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
 static __init void svm_adjust_mmio_mask(void)
 {
 	unsigned int enc_bit, mask_bit;
-	u64 msr, mask;
+	u64 msr;
 
 	/* If there is no memory encryption support, use existing mask */
 	if (cpuid_eax(0x80000000) < 0x8000001f)
@@ -4905,9 +4909,8 @@ static __init void svm_adjust_mmio_mask(void)
 	 *
 	 * If the mask bit location is 52 (or above), then clear the mask.
 	 */
-	mask = (mask_bit < 52) ? rsvd_bits(mask_bit, 51) | PT_PRESENT_MASK : 0;
-
-	kvm_mmu_set_mmio_spte_mask(mask, mask, PT_WRITABLE_MASK | PT_USER_MASK);
+	svm_shadow_mmio_mask = (mask_bit < 52) ? rsvd_bits(mask_bit, 51) | PT_PRESENT_MASK : 0;
+	kvm_mmu_set_mmio_access_mask(PT_WRITABLE_MASK | PT_USER_MASK);
 }
 
 static __init void svm_set_cpu_caps(void)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 0bce352f81b8..ec2bd4df0684 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -141,6 +141,8 @@ module_param_named(preemption_timer, enable_preemption_timer, bool, S_IRUGO);
 extern bool __read_mostly allow_smaller_maxphyaddr;
 module_param(allow_smaller_maxphyaddr, bool, S_IRUGO);
 
+u64 __ro_after_init vmx_shadow_mmio_mask;
+
 #define KVM_VM_CR0_ALWAYS_OFF (X86_CR0_NW | X86_CR0_CD)
 #define KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST X86_CR0_NE
 #define KVM_VM_CR0_ALWAYS_ON				\
@@ -7359,6 +7361,17 @@ int vmx_vm_init(struct kvm *kvm)
 	if (!ple_gap)
 		kvm->arch.pause_in_guest = true;
 
+	/*
+	 * EPT Misconfigurations can be generated if the value of bits 2:0
+	 * of an EPT paging-structure entry is 110b (write/execute).
+	 */
+	if (enable_ept)
+		kvm_mmu_set_mmio_spte_mask(kvm, VMX_EPT_MISCONFIG_WX_VALUE,
+					   VMX_EPT_RWX_MASK);
+	else
+		kvm_mmu_set_mmio_spte_mask(kvm, vmx_shadow_mmio_mask,
+					   vmx_shadow_mmio_mask);
+
 	if (boot_cpu_has(X86_BUG_L1TF) && enable_ept) {
 		switch (l1tf_mitigation) {
 		case L1TF_MITIGATION_OFF:
@@ -8357,6 +8370,19 @@ int __init vmx_init(void)
 	if (!enable_ept)
 		allow_smaller_maxphyaddr = true;
 
+	/*
+	 * Set a reserved PA bit in MMIO SPTEs to generate page faults with
+	 * PFEC.RSVD=1 on MMIO accesses.  64-bit PTEs (PAE, x86-64, and EPT
+	 * paging) support a maximum of 52 bits of PA, i.e. if the CPU supports
+	 * 52-bit physical addresses then there are no reserved PA bits in the
+	 * PTEs and so the reserved PA approach must be disabled.
+	 */
+	if (kvm_get_shadow_phys_bits() < 52)
+		vmx_shadow_mmio_mask = BIT_ULL(51) | PT_PRESENT_MASK;
+	else
+		vmx_shadow_mmio_mask = 0;
+	kvm_mmu_set_mmio_access_mask(0);
+
 	return 0;
 }
 
diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
index b4ffa1590d41..62f1d1cdd44b 100644
--- a/arch/x86/kvm/vmx/x86_ops.h
+++ b/arch/x86/kvm/vmx/x86_ops.h
@@ -13,6 +13,7 @@ void hv_vp_assist_page_exit(void);
 void __init vmx_init_early(void);
 int __init vmx_init(void);
 void vmx_exit(void);
+extern u64 __ro_after_init vmx_shadow_mmio_mask;
 
 __init int vmx_cpu_has_kvm_support(void);
 __init int vmx_disabled_by_bios(void);
-- 
2.25.1