Enable KVM FPU fully eager restore, if there is other FPU state which isn't
tracked by CR0.TS bit.
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/kvm/vmx.c | 2 ++
arch/x86/kvm/x86.c | 15 ++++++++++++++-
3 files changed, 20 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/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 248c2b4..853e875 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3028,6 +3028,8 @@ static void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
if (!vcpu->fpu_active)
hw_cr0 |= X86_CR0_TS | X86_CR0_MP;
+ else
+ hw_cr0 &= ~(X86_CR0_TS | X86_CR0_MP);
vmcs_writel(CR0_READ_SHADOW, cr0);
vmcs_writel(GUEST_CR0, hw_cr0);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 20f2266..183cf60 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -560,6 +560,8 @@ int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
return 1;
if (xcr0 & ~host_xcr0)
return 1;
+ if (xcr0 & ~((u64)KVM_XSTATE_LAZY))
+ vcpu->fpu_active = 1;
vcpu->arch.xcr0 = xcr0;
vcpu->guest_xcr0_loaded = 0;
return 0;
@@ -5969,7 +5971,18 @@ 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);
+ /*
+ * Currently KVM trigger FPU restore by #NM (via CR0.TS),
+ * till now only XCR0.bit0, XCR0.bit1, XCR0.bit2 is tracked
+ * by TS bit, there might be other FPU state is not tracked
+ * by TS bit. Here it only make FPU deactivate request and do
+ * FPU lazy restore for these cases: 1)xsave isn't enabled
+ * in guest, 2)all guest FPU states can be tracked by TS bit.
+ * For others, doing fully FPU eager restore.
+ */
+ if (!kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) ||
+ !(vcpu->arch.xcr0 & ~((u64)KVM_XSTATE_LAZY)))
+ kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu);
trace_kvm_fpu(0);
}
--
1.5.5
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