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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH V4 2/4] x86/xsaves: enable xsaves/xrstors in xen
On Wed, Aug 26, 2015 at 11:12:02AM +0100, Andrew Cooper wrote:
> On 25/08/15 11:54, Shuai Ruan wrote:
> > This patch uses xsaves/xrstors instead of xsaveopt/xrstor
> > to perform the xsave_area switching so that xen itself
> > can benefit from them when available.
> >
> > For xsaves/xrstors only use compact format. Add format conversion
> > support when perform guest os migration.
> >
> > Signed-off-by: Shuai Ruan <shuai.ruan@xxxxxxxxxxxxxxx>
> > ---
> > xen/arch/x86/domain.c | 2 +
> > xen/arch/x86/domctl.c | 34 ++++++++++++---
> > xen/arch/x86/hvm/hvm.c | 19 ++++++---
> > xen/arch/x86/i387.c | 4 ++
> > xen/arch/x86/traps.c | 7 ++--
> > xen/arch/x86/xstate.c | 112
> > ++++++++++++++++++++++++++++++++++---------------
> > 6 files changed, 132 insertions(+), 46 deletions(-)
> >
> > diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> > index 045f6ff..7b8f649 100644
> > --- a/xen/arch/x86/domain.c
> > +++ b/xen/arch/x86/domain.c
> > @@ -1529,6 +1529,8 @@ static void __context_switch(void)
> > if ( xcr0 != get_xcr0() && !set_xcr0(xcr0) )
> > BUG();
> > }
> > + if ( cpu_has_xsaves )
> > + wrmsrl(MSR_IA32_XSS, n->arch.msr_ia32_xss);
>
> This is still not appropriate. You need a per cpu variable and only
> perform lazy writes of the MSR.
>
Ok.I will introduce two helper
void set_xss_msr(uint64_t msr_xss);
uint64_t get_xss_msr();
to perform lazy writes of the MSR.
> > vcpu_restore_fpu_eager(n);
> > n->arch.ctxt_switch_to(n);
> > }
> > diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
> > index bf62a88..da136876 100644
> > --- a/xen/arch/x86/domctl.c
> > +++ b/xen/arch/x86/domctl.c
> > @@ -867,6 +867,7 @@ long arch_do_domctl(
> > if ( domctl->cmd == XEN_DOMCTL_getvcpuextstate )
> > {
> > unsigned int size;
> > + void * xsave_area;
>
> Unnecessary space.
>
Sorry.
> >
> > ret = 0;
> > vcpu_pause(v);
> > @@ -896,9 +897,28 @@ long arch_do_domctl(
> > ret = -EFAULT;
> >
> > offset += sizeof(v->arch.xcr0_accum);
> > - if ( !ret && copy_to_guest_offset(evc->buffer, offset,
> > - (void *)v->arch.xsave_area,
> > - size - 2 * sizeof(uint64_t))
> > )
> > +
> > + if ( cpu_has_xsaves )
>
> I think this would be more correct to gate on v->arch.xsave_area
> actually being compressed.
>
I will introduce a helper called
bool_t xsave_area_compressed(struct xsave_struct *xsave_area)
to check whether the area is compressed or not.
> > + {
> > + xsave_area = xmalloc_bytes(size);
> > + if ( !xsave_area )
> > + {
> > + ret = -ENOMEM;
> > + goto vcpuextstate_out;
> > + }
> > +
> > + save_xsave_states(v, xsave_area,
> > + evc->size - 2*sizeof(uint64_t));
>
> And on a similar note, save_xsave_states() is really
> uncompress_xsave_area(). On further consideration, it should ASSERT()
> that the source is currently compressed.
>
Ok.
> > +
> > + if ( !ret && copy_to_guest_offset(evc->buffer, offset,
> > + xsave_area, size -
> > + 2 * sizeof(uint64_t)) )
> > + ret = -EFAULT;
> > + xfree(xsave_area);
> > + }
> > + else if ( !ret && copy_to_guest_offset(evc->buffer, offset,
> > + (void
> > *)v->arch.xsave_area,
> > + size - 2 *
> > sizeof(uint64_t)) )
> > ret = -EFAULT;
> >
> > vcpu_unpause(v);
> > @@ -954,8 +974,12 @@ long arch_do_domctl(
> > v->arch.xcr0_accum = _xcr0_accum;
> > if ( _xcr0_accum & XSTATE_NONLAZY )
> > v->arch.nonlazy_xstate_used = 1;
> > - memcpy(v->arch.xsave_area, _xsave_area,
> > - evc->size - 2 * sizeof(uint64_t));
> > + if ( cpu_has_xsaves )
> > + load_xsave_states(v, (void *)_xsave_area,
> > + evc->size - 2*sizeof(uint64_t));
>
> Similarly, load_xsave_states() is really compress_xsave_area().
>
> You should check to see whether the area is already compressed, and just
> memcpy() in that case.
>
Ok.
> > + else
> > + memcpy(v->arch.xsave_area, (void *)_xsave_area,
> > + evc->size - 2 * sizeof(uint64_t));
> > vcpu_unpause(v);
> > }
> > else
> > diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> > index c957610..dc444ac 100644
> > --- a/xen/arch/x86/hvm/hvm.c
> > +++ b/xen/arch/x86/hvm/hvm.c
> > @@ -2148,8 +2148,12 @@ static int hvm_save_cpu_xsave_states(struct domain
> > *d, hvm_domain_context_t *h)
> > ctxt->xfeature_mask = xfeature_mask;
> > ctxt->xcr0 = v->arch.xcr0;
> > ctxt->xcr0_accum = v->arch.xcr0_accum;
> > - memcpy(&ctxt->save_area, v->arch.xsave_area,
> > - size - offsetof(struct hvm_hw_cpu_xsave, save_area));
> > + if ( cpu_has_xsaves )
>
> Stray hard tab.
>
Ok.
> > + save_xsave_states(v, (void *)&ctxt->save_area,
> > + size - offsetof(struct
> > hvm_hw_cpu_xsave,save_area));
>
> These offsetof()s can become far shorter by using offsetof(*ctxt,
> save_area).
>
> > diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
> > index 9f5a6c6..e9beec1 100644
> > --- a/xen/arch/x86/traps.c
> > +++ b/xen/arch/x86/traps.c
> > @@ -936,9 +936,10 @@ void pv_cpuid(struct cpu_user_regs *regs)
> > if ( regs->_ecx == 1 )
> > {
> > a &= XSTATE_FEATURE_XSAVEOPT |
> > - XSTATE_FEATURE_XSAVEC |
> > - (cpu_has_xgetbv1 ? XSTATE_FEATURE_XGETBV1 : 0) |
> > - (cpu_has_xsaves ? XSTATE_FEATURE_XSAVES : 0);
> > + XSTATE_FEATURE_XSAVEC;
> > + /* PV guest will not support xsaves. */
> > + /* (cpu_has_xgetbv1 ? XSTATE_FEATURE_XGETBV1 : 0) |
> > + (cpu_has_xsaves ? XSTATE_FEATURE_XSAVES : 0); */
>
> Don't leave this code commented out like this. Just delete it.
>
Sorry.
> > if ( !cpu_has_xsaves )
> > b = c = d = 0;
> > }
> > diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c
> > index 3986515..9050607 100644
> > --- a/xen/arch/x86/xstate.c
> > +++ b/xen/arch/x86/xstate.c
> > @@ -214,6 +214,11 @@ void xsave(struct vcpu *v, uint64_t mask)
> > typeof(ptr->fpu_sse.fip.sel) fcs = ptr->fpu_sse.fip.sel;
> > typeof(ptr->fpu_sse.fdp.sel) fds = ptr->fpu_sse.fdp.sel;
> >
> > + if ( cpu_has_xsaves )
> > + asm volatile ( ".byte 0x48,0x0f,0xc7,0x2f"
> > + : "=m" (*ptr)
> > + : "a" (lmask), "d" (hmask), "D" (ptr) );
> > + else
> > if ( cpu_has_xsaveopt )
>
> Please join the if() onto the previous line.
>
Ok.
> > {
> > /*
> > @@ -267,6 +272,11 @@ void xsave(struct vcpu *v, uint64_t mask)
> > }
> > else
> > {
> > + if ( cpu_has_xsaves )
> > + asm volatile ( ".byte 0x48,0x0f,0xc7,0x2f"
> > + : "=m" (*ptr)
> > + : "a" (lmask), "d" (hmask), "D" (ptr) );
> > + else
> > if ( cpu_has_xsaveopt )
>
> And here.
>
> > @@ -466,16 +508,20 @@ void xstate_init(bool_t bsp)
> > {
> > cpu_has_xsaveopt = !!(eax & XSTATE_FEATURE_XSAVEOPT);
> > cpu_has_xsavec = !!(eax & XSTATE_FEATURE_XSAVEC);
> > - /* XXX cpu_has_xgetbv1 = !!(eax & XSTATE_FEATURE_XGETBV1); */
> > - /* XXX cpu_has_xsaves = !!(eax & XSTATE_FEATURE_XSAVES); */
> > + cpu_has_xgetbv1 = !!(eax & XSTATE_FEATURE_XGETBV1);
> > + cpu_has_xsaves = !!(eax & XSTATE_FEATURE_XSAVES);
> > }
> > else
> > {
> > BUG_ON(!cpu_has_xsaveopt != !(eax & XSTATE_FEATURE_XSAVEOPT));
> > BUG_ON(!cpu_has_xsavec != !(eax & XSTATE_FEATURE_XSAVEC));
> > - /* XXX BUG_ON(!cpu_has_xgetbv1 != !(eax &
> > XSTATE_FEATURE_XGETBV1)); */
> > - /* XXX BUG_ON(!cpu_has_xsaves != !(eax & XSTATE_FEATURE_XSAVES));
> > */
> > + BUG_ON(!cpu_has_xgetbv1 != !(eax & XSTATE_FEATURE_XGETBV1));
> > + BUG_ON(!cpu_has_xsaves != !(eax & XSTATE_FEATURE_XSAVES));
> > }
> > +
> > + setup_xstate_features();
> > + if ( cpu_has_xsaves )
> > + setup_xstate_comp();
>
> setup_state_comp() should only be called on the bsp, and
> setup_xstate_features() should have a similar bsp/ap split with
> generating or validating state.
>
Ok.
> ~Andrew
>
Thanks for your review, Andrew
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