Re: [PATCH v19 080/130] KVM: TDX: restore host xsave state when exit from the guest TD

Isaku Yamahata
2024-04-12T20:19:01Z

On Sun, Apr 07, 2024 at 11:47:00AM +0800,
Binbin Wu <binbin.wu@linux.intel.com> wrote:

>
>
> On 2/26/2024 4:26 PM, isaku.yamahata@intel.com wrote:
> > From: Isaku Yamahata <isaku.yamahata@intel.com>
> >
> > On exiting from the guest TD, xsave state is clobbered. Restore xsave
> > state on TD exit.
> >
> > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> > ---
> > v19:
> > - Add EXPORT_SYMBOL_GPL(host_xcr0)
> >
> > v15 -> v16:
> > - Added CET flag mask
> >
> > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> > ---
> > arch/x86/kvm/vmx/tdx.c | 19 +++++++++++++++++++
> > arch/x86/kvm/x86.c | 1 +
> > 2 files changed, 20 insertions(+)
> >
> > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> > index 9616b1aab6ce..199226c6cf55 100644
> > --- a/arch/x86/kvm/vmx/tdx.c
> > +++ b/arch/x86/kvm/vmx/tdx.c
> > @@ -2,6 +2,7 @@
> > #include <linux/cpu.h>
> > #include <linux/mmu_context.h>
> > +#include <asm/fpu/xcr.h>
> > #include <asm/tdx.h>
> > #include "capabilities.h"
> > @@ -534,6 +535,23 @@ void tdx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
> > */
> > }
> > +static void tdx_restore_host_xsave_state(struct kvm_vcpu *vcpu)
> > +{
> > + struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm);
> > +
> > + if (static_cpu_has(X86_FEATURE_XSAVE) &&
> > + host_xcr0 != (kvm_tdx->xfam & kvm_caps.supported_xcr0))
> > + xsetbv(XCR_XFEATURE_ENABLED_MASK, host_xcr0);
> > + if (static_cpu_has(X86_FEATURE_XSAVES) &&
> > + /* PT can be exposed to TD guest regardless of KVM's XSS support */
> The comment needs to be updated to reflect the case for CET.
>
> > + host_xss != (kvm_tdx->xfam &
> > + (kvm_caps.supported_xss | XFEATURE_MASK_PT | TDX_TD_XFAM_CET)))
>
> For TDX_TD_XFAM_CET, maybe no need to make it TDX specific?
>
> BTW, the definitions for XFEATURE_MASK_CET_USER/XFEATURE_MASK_CET_KERNEL
> have been merged.
> https://lore.kernel.org/all/20230613001108.3040476-25-rick.p.edgecombe%40intel.com
> You can resolve the TODO in https://lore.kernel.org/kvm/5eca97e6a3978cf4dcf1cff21be6ec8b639a66b9.1708933498.git.isaku.yamahata@intel.com/

Yes, will update those constants to use the one in arch/x86/include/asm/fpu/types.h
--
Isaku Yamahata <isaku.yamahata@intel.com>