linux-kernel - [PATCH 1/2] nVMX: Ensure host's PAT is loaded at the end of all VMX tests

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Date: Wed,  5 Jun 2024 15:45:26 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: linux-kernel@...r.kernel.org, Xiangfei Ma <xiangfeix.ma@...el.com>, 
	Yan Zhao <yan.y.zhao@...el.com>, Sean Christopherson <seanjc@...gle.com>
Subject: [PATCH 1/2] nVMX: Ensure host's PAT is loaded at the end of all VMX tests

Load the host's original PAT on VM-Exit by default in all VMX tests, and
manually write PAT with the original value in the test that verifies all
legal PAT values can be loaded via HOST_PAT.  Failure to (re)load the
correct host PAT results in all tests that run after test_load_host_pat()
using UC memtype for all memory.

Opportunistically fix a message goof for the ENT_LOAD_PAT=0 case.

Reported-by: Xiangfei Ma <xiangfeix.ma@...el.com>
Cc: Yan Zhao <yan.y.zhao@...el.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 x86/vmx.c       | 4 +++-
 x86/vmx_tests.c | 5 ++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/x86/vmx.c b/x86/vmx.c
index 9f08c096..c803eaa6 100644
--- a/x86/vmx.c
+++ b/x86/vmx.c
@@ -1126,6 +1126,8 @@ static void init_vmcs_host(void)
 	vmcs_write(HOST_CR4, read_cr4());
 	vmcs_write(HOST_SYSENTER_EIP, (u64)(&entry_sysenter));
 	vmcs_write(HOST_SYSENTER_CS,  KERNEL_CS);
+	if (ctrl_exit_rev.clr & EXI_LOAD_PAT)
+		vmcs_write(HOST_PAT, rdmsr(MSR_IA32_CR_PAT));
 
 	/* 26.2.3 */
 	vmcs_write(HOST_SEL_CS, KERNEL_CS);
@@ -1247,7 +1249,7 @@ int init_vmcs(struct vmcs **vmcs)
 	/* All settings to pin/exit/enter/cpu
 	   control fields should be placed here */
 	ctrl_pin |= PIN_EXTINT | PIN_NMI | PIN_VIRT_NMI;
-	ctrl_exit = EXI_LOAD_EFER | EXI_HOST_64;
+	ctrl_exit = EXI_LOAD_EFER | EXI_HOST_64 | EXI_LOAD_PAT;
 	ctrl_enter = (ENT_LOAD_EFER | ENT_GUEST_64);
 	/* DIsable IO instruction VMEXIT now */
 	ctrl_cpu[0] &= (~(CPU_IO | CPU_IO_BITMAP));
diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
index 22e8812a..8a17dd90 100644
--- a/x86/vmx_tests.c
+++ b/x86/vmx_tests.c
@@ -7233,6 +7233,7 @@ static void test_guest_efer(void)
 static void test_pat(u32 field, const char * field_name, u32 ctrl_field,
 		     u64 ctrl_bit)
 {
+	u64 pat_msr_saved = rdmsr(MSR_IA32_CR_PAT);
 	u32 ctrl_saved = vmcs_read(ctrl_field);
 	u64 pat_saved = vmcs_read(field);
 	u64 i, val;
@@ -7252,7 +7253,7 @@ static void test_pat(u32 field, const char * field_name, u32 ctrl_field,
 				report_prefix_pop();
 
 			} else {	// GUEST_PAT
-				test_guest_state("ENT_LOAD_PAT enabled", false,
+				test_guest_state("ENT_LOAD_PAT disabled", false,
 						 val, "GUEST_PAT");
 			}
 		}
@@ -7274,6 +7275,8 @@ static void test_pat(u32 field, const char * field_name, u32 ctrl_field,
 					error = 0;
 
 				test_vmx_vmlaunch(error);
+				wrmsr(MSR_IA32_CR_PAT, pat_msr_saved);
+
 				report_prefix_pop();
 
 			} else {	// GUEST_PAT
-- 
2.45.1.467.gbab1589fc0-goog