Add VMX specific accessors for RIP and RSP that are used if and only if
CONFIG_RETPOLINE=y to avoid bouncing through kvm_x86_ops.cache_reg() and
taking the associated retpoline hit. This eliminates a retpoline in the
vast majority of exits by avoiding the RIP read needed to skip the
emulated instruction. This also saves two retpolines on nested VM-Exits
as both RIP and RSP need to be saved from vmcs02 to vmcs12.
Make the accessors dependent on CONFIG_RETPOLINE so that they can be
easily ripped out if/when the kernel gains support for static calls.
No functional change intended.
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/kvm/vmx/nested.c | 6 +++---
arch/x86/kvm/vmx/vmx.c | 6 +++---
arch/x86/kvm/vmx/vmx.h | 28 ++++++++++++++++++++++++++++
3 files changed, 34 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 3b4f1408b4e1..a7639818b814 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3943,8 +3943,8 @@ static void sync_vmcs02_to_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
vmcs12->guest_cr0 = vmcs12_guest_cr0(vcpu, vmcs12);
vmcs12->guest_cr4 = vmcs12_guest_cr4(vcpu, vmcs12);
- vmcs12->guest_rsp = kvm_rsp_read(vcpu);
- vmcs12->guest_rip = kvm_rip_read(vcpu);
+ vmcs12->guest_rsp = vmx_rsp_read(vcpu);
+ vmcs12->guest_rip = vmx_rip_read(vcpu);
vmcs12->guest_rflags = vmcs_readl(GUEST_RFLAGS);
vmcs12->guest_cs_ar_bytes = vmcs_read32(GUEST_CS_AR_BYTES);
@@ -5854,7 +5854,7 @@ bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu)
exit_intr_info = vmx_get_intr_info(vcpu);
exit_qual = vmx_get_exit_qual(vcpu);
- trace_kvm_nested_vmexit(kvm_rip_read(vcpu), exit_reason, exit_qual,
+ trace_kvm_nested_vmexit(vmx_rip_read(vcpu), exit_reason, exit_qual,
vmx->idt_vectoring_info, exit_intr_info,
vmcs_read32(VM_EXIT_INTR_ERROR_CODE),
KVM_ISA_VMX);
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 0cb0c347de04..d826ac541eed 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1569,7 +1569,7 @@ static int skip_emulated_instruction(struct kvm_vcpu *vcpu)
*/
if (!static_cpu_has(X86_FEATURE_HYPERVISOR) ||
to_vmx(vcpu)->exit_reason != EXIT_REASON_EPT_MISCONFIG) {
- rip = kvm_rip_read(vcpu);
+ rip = vmx_rip_read(vcpu);
rip += vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
kvm_rip_write(vcpu, rip);
} else {
@@ -2185,7 +2185,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return ret;
}
-static void vmx_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
+void vmx_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
{
unsigned long guest_owned_bits;
@@ -4750,7 +4750,7 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
vmx->vcpu.arch.event_exit_inst_len =
vmcs_read32(VM_EXIT_INSTRUCTION_LEN);
kvm_run->exit_reason = KVM_EXIT_DEBUG;
- rip = kvm_rip_read(vcpu);
+ rip = vmx_rip_read(vcpu);
kvm_run->debug.arch.pc = vmcs_readl(GUEST_CS_BASE) + rip;
kvm_run->debug.arch.exception = ex_no;
break;
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 5f3f141d7254..63baa0d5fe41 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -500,6 +500,34 @@ static inline struct pi_desc *vcpu_to_pi_desc(struct kvm_vcpu *vcpu)
return &(to_vmx(vcpu)->pi_desc);
}
+#ifdef CONFIG_RETPOLINE
+void vmx_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg);
+static __always_inline unsigned long vmx_register_read(struct kvm_vcpu *vcpu,
+ enum kvm_reg reg)
+{
+ BUILD_BUG_ON(!__builtin_constant_p(reg));
+ BUILD_BUG_ON(reg != VCPU_REGS_RIP && reg != VCPU_REGS_RSP);
+
+ if (!kvm_register_is_available(vcpu, reg))
+ vmx_cache_reg(vcpu, reg);
+
+ return vcpu->arch.regs[reg];
+}
+
+static inline unsigned long vmx_rip_read(struct kvm_vcpu *vcpu)
+{
+ return vmx_register_read(vcpu, VCPU_REGS_RIP);
+}
+
+static inline unsigned long vmx_rsp_read(struct kvm_vcpu *vcpu)
+{
+ return vmx_register_read(vcpu, VCPU_REGS_RSP);
+}
+#else
+#define vmx_rip_read kvm_rip_read
+#define vmx_rsp_read kvm_rsp_read
+#endif
+
static inline unsigned long vmx_get_exit_qual(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
--
2.26.0
