linux-kernel - [PATCH 29/54] KVM: x86/mmu: Don't grab CR4.PSE for calculating shadow reserved bits

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Message-Id: <20210622175739.3610207-30-seanjc@google.com>
Date:   Tue, 22 Jun 2021 10:57:14 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH 29/54] KVM: x86/mmu: Don't grab CR4.PSE for calculating shadow
 reserved bits

Unconditionally pass pse=false when calculating reserved bits for shadow
PTEs.  CR4.PSE is only relevant for 32-bit non-PAE paging, which KVM does
not use for shadow paging (including nested NPT).

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/mmu/mmu.c | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 337a3e571db6..ffcaede019e4 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4281,19 +4281,22 @@ static void reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
 	 * MMU contexts.  Note, KVM forces EFER.NX=1 when TDP is disabled.
 	 */
 	bool uses_nx = context->nx || !tdp_enabled;
+
+	/* @amd adds a check on bit of SPTEs, which KVM shouldn't use anyways. */
+	bool is_amd = true;
+	/* KVM doesn't use 2-level page tables for the shadow MMU. */
+	bool is_pse = false;
 	struct rsvd_bits_validate *shadow_zero_check;
 	int i;
 
-	/*
-	 * Passing "true" to the last argument is okay; it adds a check
-	 * on bit 8 of the SPTEs which KVM doesn't use anyway.
-	 */
+	WARN_ON_ONCE(context->shadow_root_level < PT32E_ROOT_LEVEL);
+
 	shadow_zero_check = &context->shadow_zero_check;
 	__reset_rsvds_bits_mask(vcpu, shadow_zero_check,
 				reserved_hpa_bits(),
 				context->shadow_root_level, uses_nx,
 				guest_cpuid_has(vcpu, X86_FEATURE_GBPAGES),
-				is_pse(vcpu), true);
+				is_pse, is_amd);
 
 	if (!shadow_me_mask)
 		return;
@@ -4329,7 +4332,7 @@ reset_tdp_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
 					reserved_hpa_bits(),
 					context->shadow_root_level, false,
 					boot_cpu_has(X86_FEATURE_GBPAGES),
-					true, true);
+					false, true);
 	else
 		__reset_rsvds_bits_mask_ept(shadow_zero_check,
 					    reserved_hpa_bits(), false);
-- 
2.32.0.288.g62a8d224e6-goog