linux-kernel - [PATCH v2 1/3] KVM: x86: dump_vmcs should not assume GUEST_IA32

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Date:   Fri, 19 Feb 2021 14:46:30 +0000
From:   David Edmondson <david.edmondson@...cle.com>
To:     linux-kernel@...r.kernel.org
Cc:     "H. Peter Anvin" <hpa@...or.com>, Joerg Roedel <joro@...tes.org>,
        x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
        kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Ingo Molnar <mingo@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Borislav Petkov <bp@...en8.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        David Edmondson <david.edmondson@...cle.com>
Subject: [PATCH v2 1/3] KVM: x86: dump_vmcs should not assume GUEST_IA32_EFER is valid

If the VM entry/exit controls for loading/saving MSR_EFER are either
not available (an older processor or explicitly disabled) or not
used (host and guest values are the same), reading GUEST_IA32_EFER
from the VMCS returns an inaccurate value.

Because of this, in dump_vmcs() don't use GUEST_IA32_EFER to decide
whether to print the PDPTRs - do so if the EPT is in use and CR4.PAE
is set.

Fixes: 4eb64dce8d0a ("KVM: x86: dump VMCS on invalid entry")
Signed-off-by: David Edmondson <david.edmondson@...cle.com>
---
 arch/x86/kvm/vmx/vmx.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index eb69fef57485..818051c9fa10 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5759,7 +5759,6 @@ void dump_vmcs(void)
 	u32 vmentry_ctl, vmexit_ctl;
 	u32 cpu_based_exec_ctrl, pin_based_exec_ctrl, secondary_exec_control;
 	unsigned long cr4;
-	u64 efer;
 
 	if (!dump_invalid_vmcs) {
 		pr_warn_ratelimited("set kvm_intel.dump_invalid_vmcs=1 to dump internal KVM state.\n");
@@ -5771,7 +5770,6 @@ void dump_vmcs(void)
 	cpu_based_exec_ctrl = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL);
 	pin_based_exec_ctrl = vmcs_read32(PIN_BASED_VM_EXEC_CONTROL);
 	cr4 = vmcs_readl(GUEST_CR4);
-	efer = vmcs_read64(GUEST_IA32_EFER);
 	secondary_exec_control = 0;
 	if (cpu_has_secondary_exec_ctrls())
 		secondary_exec_control = vmcs_read32(SECONDARY_VM_EXEC_CONTROL);
@@ -5784,8 +5782,7 @@ void dump_vmcs(void)
 	       cr4, vmcs_readl(CR4_READ_SHADOW), vmcs_readl(CR4_GUEST_HOST_MASK));
 	pr_err("CR3 = 0x%016lx\n", vmcs_readl(GUEST_CR3));
 	if ((secondary_exec_control & SECONDARY_EXEC_ENABLE_EPT) &&
-	    (cr4 & X86_CR4_PAE) && !(efer & EFER_LMA))
-	{
+	    (cr4 & X86_CR4_PAE)) {
 		pr_err("PDPTR0 = 0x%016llx  PDPTR1 = 0x%016llx\n",
 		       vmcs_read64(GUEST_PDPTR0), vmcs_read64(GUEST_PDPTR1));
 		pr_err("PDPTR2 = 0x%016llx  PDPTR3 = 0x%016llx\n",
@@ -5811,7 +5808,8 @@ void dump_vmcs(void)
 	if ((vmexit_ctl & (VM_EXIT_SAVE_IA32_PAT | VM_EXIT_SAVE_IA32_EFER)) ||
 	    (vmentry_ctl & (VM_ENTRY_LOAD_IA32_PAT | VM_ENTRY_LOAD_IA32_EFER)))
 		pr_err("EFER =     0x%016llx  PAT = 0x%016llx\n",
-		       efer, vmcs_read64(GUEST_IA32_PAT));
+		       vmcs_read64(GUEST_IA32_EFER),
+		       vmcs_read64(GUEST_IA32_PAT));
 	pr_err("DebugCtl = 0x%016llx  DebugExceptions = 0x%016lx\n",
 	       vmcs_read64(GUEST_IA32_DEBUGCTL),
 	       vmcs_readl(GUEST_PENDING_DBG_EXCEPTIONS));
-- 
2.30.0