On 09/06/2012 05:13 AM, Hao, Xudong wrote: >> -----Original Message----- >> From: Avi Kivity [mailto:avi@xxxxxxxxxx] >> Sent: Wednesday, September 05, 2012 9:13 PM >> To: Hao, Xudong >> Cc: kvm@xxxxxxxxxxxxxxx; Zhang, Xiantao; Joerg.Roedel@xxxxxxx >> Subject: Re: [PATCH v2] kvm/fpu: Enable fully eager restore kvm FPU >> >> On 09/05/2012 04:26 AM, Xudong Hao wrote: >> > Enable KVM FPU fully eager restore, if there is other FPU state which isn't >> > tracked by CR0.TS bit. >> > >> > 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/x86.c | 13 ++++++++++++- >> > 2 files changed, 16 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/x86.c b/arch/x86/kvm/x86.c >> > index 20f2266..a632042 100644 >> > --- a/arch/x86/kvm/x86.c >> > +++ b/arch/x86/kvm/x86.c >> > @@ -5969,7 +5969,18 @@ 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); >> > } >> > >> >> I think something is missing. This patch prevents >> KVM_REQ_DEACTIVATE_FPU, but the fpu may not be active when non-lazy bits >> are added to xcr0 (or cr4.osxsave is enabled). I think you need to >> activate the fpu at that time as well. >> > > Mmh, I thought fpu is active by default, but it's better to make fpu active explicitly here. > If the following patch is fine, I'll make it another version. > It is, but a previous pass through kvm_put_guest_fpu() could have deactivated it. > - kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu); > + if (kvm_read_cr4_bits(vcpu, X86_CR4_OSXSAVE) && > + (vcpu->arch.xcr0 & ~((u64)KVM_XSTATE_LAZY))) > + kvm_x86_ops->fpu_activate(vcpu); > + else > + kvm_make_request(KVM_REQ_DEACTIVATE_FPU, vcpu); > Doesn't help. We can have: host: deactivate fpu for some reason guest: set cr4.osxsave, xcr0.bit3 host: enter guest with deactivated fpu guest: touch fpu result: host fpu corrupted. -- error compiling committee.c: too many arguments to function -- 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
