[PATCH] KVM: SVM: Propagate Translation Cache Extensions to the guest

[Yosry Ahmed]

From: Venkatesh Srinivas <venkateshs@xxxxxxxxxxxx>

TCE augments the behavior of TLB invalidating instructions (INVLPG,
INVLPGB, and INVPCID) to only invalidate translations for relevant
intermediate mappings to the address range, rather than ALL intermdiate
translations.

The Linux kernel has been setting EFER.TCE if supported by the CPU since
commit 440a65b7d25f ("x86/mm: Enable AMD translation cache extensions"),
as it may improve performance.

KVM does not need to do anything to virtualize the feature, only
advertise it and allow setting EFER.TCE.  Passthrough X86_FEATURE_TCE to
the guest, and allow the guest to set EFER.TCE if available.

Co-developed-by: Yosry Ahmed <yosry@xxxxxxxxxx>
Signed-off-by: Yosry Ahmed <yosry@xxxxxxxxxx>
Signed-off-by: Venkatesh Srinivas <venkateshs@xxxxxxxxxxxx>
---
 arch/x86/kvm/cpuid.c   | 1 +
 arch/x86/kvm/svm/svm.c | 3 +++
 arch/x86/kvm/x86.c     | 3 +++
 3 files changed, 7 insertions(+)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index fffbf087937d4..4f810f23b1d9b 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1112,6 +1112,7 @@ void kvm_initialize_cpu_caps(void)
 		F(XOP),
 		/* SKINIT, WDT, LWP */
 		F(FMA4),
+		F(TCE),
 		F(TBM),
 		F(TOPOEXT),
 		VENDOR_F(PERFCTR_CORE),
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 3407deac90bd6..fee1c8cd45973 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -5580,6 +5580,9 @@ static __init int svm_hardware_setup(void)
 	if (boot_cpu_has(X86_FEATURE_AUTOIBRS))
 		kvm_enable_efer_bits(EFER_AUTOIBRS);
 
+	if (boot_cpu_has(X86_FEATURE_TCE))
+		kvm_enable_efer_bits(EFER_TCE);
+
 	/* Check for pause filtering support */
 	if (!boot_cpu_has(X86_FEATURE_PAUSEFILTER)) {
 		pause_filter_count = 0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 879cdeb6adde2..7336ce1df3f7a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1743,6 +1743,9 @@ static bool __kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer)
 	if (efer & EFER_NX && !guest_cpu_cap_has(vcpu, X86_FEATURE_NX))
 		return false;
 
+	if (efer & EFER_TCE && !guest_cpu_cap_has(vcpu, X86_FEATURE_TCE))
+		return false;
+
 	return true;
 
 }

base-commit: 5128b972fb2801ad9aca54d990a75611ab5283a9
-- 
2.53.0.473.g4a7958ca14-goog