On Thu, Sep 13, 2012 at 01:26:36PM -0300, Marcelo Tosatti wrote:
> On Wed, Sep 12, 2012 at 04:10:24PM +0800, Xudong Hao wrote:
> > 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.
>
> How about a "guest_xcr0_can_lazy_saverestore" bool to control this?
> It only needs to be updated when guest xcr0 is updated.
>
> That seems cleaner. Avi?
Reasoning below.
> > 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;
This is confusing. The variable allows to decrease the number of places
the decision is made.
> > 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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