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Message-ID: <Y6v287BFez8tU43e@yzhao56-desk.sh.intel.com> Date: Wed, 28 Dec 2022 15:57:39 +0800 From: Yan Zhao <yan.y.zhao@...el.com> To: Sean Christopherson <seanjc@...gle.com> CC: Paolo Bonzini <pbonzini@...hat.com>, Zhenyu Wang <zhenyuw@...ux.intel.com>, Zhi Wang <zhi.a.wang@...el.com>, <kvm@...r.kernel.org>, <intel-gvt-dev@...ts.freedesktop.org>, <intel-gfx@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>, Ben Gardon <bgardon@...gle.com> Subject: Re: [PATCH 26/27] KVM: x86/mmu: Add page-track API to query if a gfn is valid On Fri, Dec 23, 2022 at 12:57:38AM +0000, Sean Christopherson wrote: > Add a page-track API to query if a gfn is "valid", i.e. is backed by a > memslot and is visible to the guest. This is one more step toward > removing KVM internal details from the page-track APIs. > > Add a FIXME to call out that intel_gvt_is_valid_gfn() is broken with > respect to 2MiB (or larger) guest entries, e.g. if the starting gfn is > valid but a 2MiB page starting at the gfn covers "invalid" memory due > to running beyond the memslot. > > No functional change intended. > > Signed-off-by: Sean Christopherson <seanjc@...gle.com> > --- > arch/x86/include/asm/kvm_page_track.h | 1 + > arch/x86/kvm/mmu/page_track.c | 13 +++++++++++++ > drivers/gpu/drm/i915/gvt/gtt.c | 11 ++--------- > 3 files changed, 16 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_page_track.h b/arch/x86/include/asm/kvm_page_track.h > index 66a0d7c34311..99e1d6eeb0fb 100644 > --- a/arch/x86/include/asm/kvm_page_track.h > +++ b/arch/x86/include/asm/kvm_page_track.h > @@ -52,6 +52,7 @@ int kvm_page_track_register_notifier(struct kvm *kvm, > void kvm_page_track_unregister_notifier(struct kvm *kvm, > struct kvm_page_track_notifier_node *n); > > +bool kvm_page_track_is_valid_gfn(struct kvm *kvm, gfn_t gfn); > int kvm_write_track_add_gfn(struct kvm *kvm, gfn_t gfn); > int kvm_write_track_remove_gfn(struct kvm *kvm, gfn_t gfn); > #endif /* CONFIG_KVM_EXTERNAL_WRITE_TRACKING */ > diff --git a/arch/x86/kvm/mmu/page_track.c b/arch/x86/kvm/mmu/page_track.c > index 1af431a41f71..9da071a514b3 100644 > --- a/arch/x86/kvm/mmu/page_track.c > +++ b/arch/x86/kvm/mmu/page_track.c > @@ -264,6 +264,19 @@ enum pg_level kvm_page_track_max_mapping_level(struct kvm *kvm, gfn_t gfn, > } > EXPORT_SYMBOL_GPL(kvm_page_track_max_mapping_level); > > +bool kvm_page_track_is_valid_gfn(struct kvm *kvm, gfn_t gfn) > +{ > + bool ret; > + int idx; > + > + idx = srcu_read_lock(&kvm->srcu); > + ret = kvm_is_visible_gfn(kvm, gfn); > + srcu_read_unlock(&kvm->srcu, idx); > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(kvm_page_track_is_valid_gfn); This implementation is only to check whether a GFN is within a visible kvm memslot. So, why this helper function is named kvm_page_track_xxx()? Don't think it's anything related to page track, and not all of its callers in KVMGT are for page tracking. Thanks Yan > + > /* > * add guest page to the tracking pool so that corresponding access on that > * page will be intercepted. > diff --git a/drivers/gpu/drm/i915/gvt/gtt.c b/drivers/gpu/drm/i915/gvt/gtt.c > index 59ba6639e622..43c4fc23205d 100644 > --- a/drivers/gpu/drm/i915/gvt/gtt.c > +++ b/drivers/gpu/drm/i915/gvt/gtt.c > @@ -51,18 +51,11 @@ static int preallocated_oos_pages = 8192; > > static bool intel_gvt_is_valid_gfn(struct intel_vgpu *vgpu, unsigned long gfn) > { > - struct kvm *kvm = vgpu->vfio_device.kvm; > - int idx; > - bool ret; > - > if (!vgpu->attached) > return false; > > - idx = srcu_read_lock(&kvm->srcu); > - ret = kvm_is_visible_gfn(kvm, gfn); > - srcu_read_unlock(&kvm->srcu, idx); > - > - return ret; > + /* FIXME: This doesn't properly handle guest entries larger than 4K. */ > + return kvm_page_track_is_valid_gfn(vgpu->vfio_device.kvm, gfn); > } > > /* > -- > 2.39.0.314.g84b9a713c41-goog >
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