linux-kernel - [PATCH v10 036/108] KVM: TDX: Enable mmio spte caching always for TDX

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Message-Id: <820bac8ce45b92d643630084096dcd7e71038a58.1667110240.git.isaku.yamahata@intel.com>
Date:   Sat, 29 Oct 2022 23:22:37 -0700
From:   isaku.yamahata@...el.com
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
        Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>
Subject: [PATCH v10 036/108] KVM: TDX: Enable mmio spte caching always for TDX

From: Isaku Yamahata <isaku.yamahata@...el.com>

TDX needs to set shared spte for MMIO GFN to !SUPPRES_VE_BIT | !RWX so that
guest TD can get #VE and then issue TDG.VP.VMCALL<MMIO>.  Enable mmio
caching always for TDX irrelevant the module parameter enable_mmio_caching.

Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
 arch/x86/kvm/mmu/mmu.c     | 3 ++-
 arch/x86/kvm/mmu/spte.h    | 2 +-
 arch/x86/kvm/mmu/tdp_mmu.c | 7 +++++++
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 0d3fa29ccccc..9098f77cdaa4 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3229,7 +3229,8 @@ 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(!enable_mmio_caching &&
+			     !kvm_gfn_shared_mask(vcpu->kvm)) ||
 		    unlikely(fault->gfn > kvm_mmu_max_gfn()))
 			return RET_PF_EMULATE;
 	}
diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h
index 82f0d5c08b77..fecfdcb5f321 100644
--- a/arch/x86/kvm/mmu/spte.h
+++ b/arch/x86/kvm/mmu/spte.h
@@ -244,7 +244,7 @@ extern u64 __read_mostly shadow_nonpresent_or_rsvd_lower_gfn_mask;
 static inline bool is_mmio_spte(struct kvm *kvm, u64 spte)
 {
 	return (spte & shadow_mmio_mask) == kvm->arch.shadow_mmio_value &&
-	       likely(enable_mmio_caching);
+	       likely(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 e07f14351d14..3325633b1cb5 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1875,6 +1875,13 @@ 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_ONCE(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;
-- 
2.25.1