Re: [PATCH RESEND v4 5/9] KVM: VMX: Add init/set/get functions for SPP

Yang Weijiang
2019-08-14T14:32:28Z

On Wed, Aug 14, 2019 at 02:43:39PM +0200, Vitaly Kuznetsov wrote:
> Yang Weijiang <weijiang.yang@intel.com> writes:
>
> > init_spp() must be called before {get, set}_subpage
> > functions, it creates subpage access bitmaps for memory pages
> > and issues a KVM request to setup SPPT root pages.
> >
> > kvm_mmu_set_subpages() is to enable SPP bit in EPT leaf page
> > and setup corresponding SPPT entries. The mmu_lock
> > is held before above operation. If it's called in EPT fault and
> > SPPT mis-config induced handler, mmu_lock is acquired outside
> > the function, otherwise, it's acquired inside it.
> >
> > kvm_mmu_get_subpages() is used to query access bitmap for
> > protected page, it's also used in EPT fault handler to check
> > whether the fault EPT page is SPP protected as well.
> >
> > Co-developed-by: He Chen <he.chen@linux.intel.com>
> > Signed-off-by: He Chen <he.chen@linux.intel.com>
> > Co-developed-by: Zhang Yi <yi.z.zhang@linux.intel.com>
> > Signed-off-by: Zhang Yi <yi.z.zhang@linux.intel.com>
> > Signed-off-by: Yang Weijiang <weijiang.yang@intel.com>
> > ---
> > arch/x86/include/asm/kvm_host.h | 18 ++++
> > arch/x86/include/asm/vmx.h | 2 +
> > arch/x86/kvm/mmu.c | 160 ++++++++++++++++++++++++++++++++
> > arch/x86/kvm/vmx/vmx.c | 48 ++++++++++
> > arch/x86/kvm/x86.c | 40 ++++++++
> > include/linux/kvm_host.h | 4 +-
> > include/uapi/linux/kvm.h | 9 ++
> > 7 files changed, 280 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > index 44f6e1757861..5c4882015acc 100644
> > --- a/arch/x86/include/asm/kvm_host.h
> > +++ b/arch/x86/include/asm/kvm_host.h
> > @@ -398,8 +398,13 @@ struct kvm_mmu {
> > void (*invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa);
> > void (*update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
> > u64 *spte, const void *pte);
> > + int (*get_subpages)(struct kvm *kvm, struct kvm_subpage *spp_info);
> > + int (*set_subpages)(struct kvm *kvm, struct kvm_subpage *spp_info);
> > + int (*init_spp)(struct kvm *kvm);
> > +
> > hpa_t root_hpa;
> > gpa_t root_cr3;
> > + hpa_t sppt_root;
>
> (I'm sorry if this was previously discussed, I didn't look into previous
> submissions).
>
> What happens when we launch a nested guest and switch vcpu->arch.mmu to
> point at arch.guest_mmu? sppt_root will point to INVALID_PAGE and SPP
> won't be enabled in VMCS?
>
> (I'm sorry again, I'm likely missing something obvious)
>
> --
> Vitaly

Hi, Vitaly,
Thanks for raising a good qeustion, I must have missed the nested case,
I'll double check how to support the nested case.