TDX requires guests to accept S-EPT mappings created by the host KVM. Due to the current implementation of the TDX module, if a guest accepts a GFN at a lower level after KVM maps it at a higher level, the TDX module will emulate an EPT violation VMExit to KVM instead of returning a size mismatch error to the guest. If KVM fails to perform page splitting in the VMExit handler, the guest's accept operation will be triggered again upon re-entering the guest, causing a repeated EPT violation VMExit. To facilitate passing the guest's accept level information to the KVM MMU core and to prevent the repeated mapping of a GFN at different levels due to different accept levels specified by different vCPUs, introduce the interface hugepage_set_guest_inhibit(). This interface specifies across vCPUs that mapping at a certain level is inhibited from the guest. The KVM_LPAGE_GUEST_INHIBIT_FLAG bit is currently modified in one direction (set), so no clear interface is provided. Link: https://lore.kernel.org/all/a6ffe23fb97e64109f512fa43e9f6405236ed40a.camel@xxxxxxxxx/ [1] Suggested-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx> Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx> Signed-off-by: Yan Zhao <yan.y.zhao@xxxxxxxxx> --- RFC v2: - new in RFC v2 --- arch/x86/kvm/mmu.h | 3 +++ arch/x86/kvm/mmu/mmu.c | 21 ++++++++++++++++++--- 2 files changed, 21 insertions(+), 3 deletions(-) diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index b122255c7d4e..c2d8819f3438 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -326,4 +326,7 @@ static inline bool kvm_is_gfn_alias(struct kvm *kvm, gfn_t gfn) { return gfn & kvm_gfn_direct_bits(kvm); } + +void hugepage_set_guest_inhibit(struct kvm_memory_slot *slot, gfn_t gfn, int level); +bool hugepage_test_guest_inhibit(struct kvm_memory_slot *slot, gfn_t gfn, int level); #endif diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 13910ae05f76..1c639286aac2 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -721,12 +721,14 @@ static struct kvm_lpage_info *lpage_info_slot(gfn_t gfn, } /* - * The most significant bit in disallow_lpage tracks whether or not memory - * attributes are mixed, i.e. not identical for all gfns at the current level. + * The most 2 significant bits in disallow_lpage tracks whether or not memory + * attributes are mixed, i.e. not identical for all gfns at the current level, + * or whether or not guest inhibits the current level of hugepage at the gfn. * The lower order bits are used to refcount other cases where a hugepage is * disallowed, e.g. if KVM has shadow a page table at the gfn. */ #define KVM_LPAGE_MIXED_FLAG BIT(31) +#define KVM_LPAGE_GUEST_INHIBIT_FLAG BIT(30) static void update_gfn_disallow_lpage_count(const struct kvm_memory_slot *slot, gfn_t gfn, int count) @@ -739,7 +741,8 @@ static void update_gfn_disallow_lpage_count(const struct kvm_memory_slot *slot, old = linfo->disallow_lpage; linfo->disallow_lpage += count; - WARN_ON_ONCE((old ^ linfo->disallow_lpage) & KVM_LPAGE_MIXED_FLAG); + WARN_ON_ONCE((old ^ linfo->disallow_lpage) & + (KVM_LPAGE_MIXED_FLAG | KVM_LPAGE_GUEST_INHIBIT_FLAG)); } } @@ -1647,6 +1650,18 @@ static bool __kvm_rmap_zap_gfn_range(struct kvm *kvm, start, end - 1, can_yield, true, flush); } +bool hugepage_test_guest_inhibit(struct kvm_memory_slot *slot, gfn_t gfn, int level) +{ + return lpage_info_slot(gfn, slot, level)->disallow_lpage & KVM_LPAGE_GUEST_INHIBIT_FLAG; +} +EXPORT_SYMBOL_GPL(hugepage_test_guest_inhibit); + +void hugepage_set_guest_inhibit(struct kvm_memory_slot *slot, gfn_t gfn, int level) +{ + lpage_info_slot(gfn, slot, level)->disallow_lpage |= KVM_LPAGE_GUEST_INHIBIT_FLAG; +} +EXPORT_SYMBOL_GPL(hugepage_set_guest_inhibit); + /* * Split large leafs crossing the boundary of the specified range * -- 2.43.2
