Enable KVM FPU fully eager restore, if there is other FPU state which isn't
tracked by CR0.TS bit.
v4 changes from v3:
- Wrap up some confused code with a clear functio lazy_fpu_allowed()
- Update fpu while update cr4 too.
v3 changes from v2:
- Make fpu active explicitly while guest xsave is enabling and non-lazy xstate
bit exist.
v2 changes from v1:
- Expand KVM_XSTATE_LAZY to 64 bits before negating it.
Signed-off-by: Xudong Hao <xudong.hao@xxxxxxxxx>
---
arch/x86/include/asm/kvm.h | 4 ++++
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/svm.c | 1 +
arch/x86/kvm/vmx.c | 1 +
arch/x86/kvm/x86.c | 32 +++++++++++++++++++++++++++++++-
5 files changed, 38 insertions(+), 1 deletions(-)
diff --git a/arch/x86/include/asm/kvm.h b/arch/x86/include/asm/kvm.h
index 521bf25..4c27056 100644
--- a/arch/x86/include/asm/kvm.h
+++ b/arch/x86/include/asm/kvm.h
@@ -8,6 +8,8 @@
#include <linux/types.h>
#include <linux/ioctl.h>
+#include <asm/user.h>
+#include <asm/xsave.h>
/* Select x86 specific features in <linux/kvm.h> */
#define __KVM_HAVE_PIT
@@ -30,6 +32,8 @@
/* Architectural interrupt line count. */
#define KVM_NR_INTERRUPTS 256
+#define KVM_XSTATE_LAZY (XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
+
struct kvm_memory_alias {
__u32 slot; /* this has a different namespace than memory slots */
__u32 flags;
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 0b902c9..25fef9e 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -826,6 +826,7 @@ unsigned long kvm_get_cr8(struct kvm_vcpu *vcpu);
void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw);
void kvm_get_cs_db_l_bits(struct kvm_vcpu *vcpu, int *db, int *l);
int kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr);
+void update_lazy_fpu(struct kvm_vcpu *vcpu);
int kvm_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data);
diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 818fceb..fbdb44a 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2941,6 +2941,7 @@ static int cr_interception(struct vcpu_svm *svm)
break;
case 4:
err = kvm_set_cr4(&svm->vcpu, val);
+ update_lazy_fpu(vcpu);
break;
case 8:
err = kvm_set_cr8(&svm->vcpu, val);
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 30bcb95..b3880c0 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4488,6 +4488,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
return 1;
case 4:
err = handle_set_cr4(vcpu, val);
+ update_lazy_fpu(vcpu);
kvm_complete_insn_gp(vcpu, err);
return 1;
case 8: {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fc2a0a1..2e14cec 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -544,6 +544,31 @@ void kvm_lmsw(struct kvm_vcpu *vcpu, unsigned long msw)
}
EXPORT_SYMBOL_GPL(kvm_lmsw);
+/*
+ * KVM trigger FPU restore by #NM (via CR0.TS),
+ * only XCR0.bit0, XCR0.bit1, XCR0.bit2 is tracked
+ * by TS bit, there might be other FPU state is not tracked
+ * by TS bit.
+ * This function lazy_fpu_allowed() return true with any of
+ * the following cases: 1)xsave isn't enabled in guest;
+ * 2)all guest FPU states can be tracked by TS bit.
+ */
+static bool lazy_fpu_allowed(struct kvm_vcpu *vcpu)
+{
+ return !!(!kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) ||
+ !(vcpu->arch.xcr0 & ~((u64)KVM_XSTATE_LAZY)));
+}
+
+void update_lazy_fpu(struct kvm_vcpu *vcpu)
+{
+ if (lazy_fpu_allowed(vcpu)) {
+ vcpu->fpu_active = 0;
+ kvm_x86_ops->fpu_deactivate(vcpu);
+ }
+ else
+ kvm_x86_ops->fpu_activate(vcpu);
+}
+
int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
{
u64 xcr0;
@@ -571,6 +596,7 @@ int kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
kvm_inject_gp(vcpu, 0);
return 1;
}
+ update_lazy_fpu(vcpu);
return 0;
}
EXPORT_SYMBOL_GPL(kvm_set_xcr);
@@ -5985,7 +6011,11 @@ void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
vcpu->guest_fpu_loaded = 0;
fpu_save_init(&vcpu->arch.guest_fpu);
++vcpu->stat.fpu_reload;
- kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu);
+ /*
+ * Make deactivate request while allow fpu lazy restore.
+ */
+ if (lazy_fpu_allowed(vcpu))
+ kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu);
trace_kvm_fpu(0);
}
--
1.5.5
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