> -----Original Message----- > From: Marcelo Tosatti [mailto:mtosatti@xxxxxxxxxx] > Sent: Monday, September 17, 2012 9:31 PM > To: Hao, Xudong > Cc: Avi Kivity; kvm@xxxxxxxxxxxxxxx; Zhang, Xiantao > Subject: Re: [PATCH v3] kvm/fpu: Enable fully eager restore kvm FPU > > On Mon, Sep 17, 2012 at 02:07:43AM +0000, Hao, Xudong wrote: > > > -----Original Message----- > > > From: Avi Kivity [mailto:avi@xxxxxxxxxx] > > > Sent: Friday, September 14, 2012 12:40 AM > > > To: Marcelo Tosatti > > > Cc: Hao, Xudong; kvm@xxxxxxxxxxxxxxx; Zhang, Xiantao > > > Subject: Re: [PATCH v3] kvm/fpu: Enable fully eager restore kvm FPU > > > > > > On 09/13/2012 07:29 PM, Marcelo Tosatti wrote: > > > > 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. > > > > > > Better to have a helper function (lazy_fpu_allowed(), for example). > > > Variables raise the question of whether they are maintained correctly. > > > > > > > I realized to modifying the fpu_active variable is incorrect, it must update > exception bitmap. > > To avoid the cr0 and xcrs setting order for live migrate case, how about > calling fpu_activate() in kvm_set_xcr()? I can add code comments in this > function calling. > > The objective of the change is to disable lazy fpu loading (that is, > host fpu loaded in guest and vice-versa), when some bit except the > initial tree bits set in guest XCR0 (initial tree being XSTATE_FP|XSTATE_SSE| > XSTATE_YMM). Yes? > Yes, it's just the object. > If i get that right, then the suggestion seems to be: > > static bool lazy_fpu_allowed() > { > return (vcpu->arch.xcr0 & ~((u64)KVM_XSTATE_LAZY)); > } > That may be: static bool lazy_fpu_allowed() { return !(vcpu->arch.xcr0 & ~((u64)KVM_XSTATE_LAZY)); } > On guest entry: > if (!lazy_fpu_allowed(vcpu)) > kvm_x86_ops->fpu_activate(vcpu); Yes, we can add it into guest entry: kvm_set_xcr(). Avi, other comments? > if (vcpu->fpu_active) > kvm_load_guest_fpu(vcpu); > > > Does that make sense? > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
