linux-kernel - [PATCH 3.16 01/25] KVM: Introduce kvm_get_arch

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Message-ID: <lsq.1573602477.270388076@decadent.org.uk>
Date:   Tue, 12 Nov 2019 23:47:58 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>
Subject: [PATCH 3.16 01/25] KVM: Introduce kvm_get_arch_capabilities()

3.16.77-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Ben Hutchings <ben@...adent.org.uk>

Extracted from commit 5b76a3cff011 "KVM: VMX: Tell the nested
hypervisor to skip L1D flush on vmentry".  We will need this to let a
nested hypervisor know that we have applied the mitigation for TAA.

Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/x86.c              | 13 +++++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1062,6 +1062,7 @@ int kvm_arch_interrupt_allowed(struct kv
 int kvm_cpu_get_interrupt(struct kvm_vcpu *v);
 void kvm_vcpu_reset(struct kvm_vcpu *vcpu);
 
+u64 kvm_get_arch_capabilities(void);
 void kvm_define_shared_msr(unsigned index, u32 msr);
 int kvm_set_shared_msr(unsigned index, u64 val, u64 mask);
 
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -911,6 +911,16 @@ static u32 emulated_msrs[] = {
 
 static unsigned num_emulated_msrs;
 
+u64 kvm_get_arch_capabilities(void)
+{
+	u64 data;
+
+	rdmsrl_safe(MSR_IA32_ARCH_CAPABILITIES, &data);
+
+	return data;
+}
+EXPORT_SYMBOL_GPL(kvm_get_arch_capabilities);
+
 bool kvm_valid_efer(struct kvm_vcpu *vcpu, u64 efer)
 {
 	if (efer & efer_reserved_bits)
@@ -6969,8 +6979,7 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu
 	int r;
 
 	if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))
-		rdmsrl(MSR_IA32_ARCH_CAPABILITIES,
-		       vcpu->arch.arch_capabilities);
+		vcpu->arch.arch_capabilities = kvm_get_arch_capabilities();
 	vcpu->arch.mtrr_state.have_fixed = 1;
 	r = vcpu_load(vcpu);
 	if (r)