On Tue, May 14, 2024 at 05:59:39PM -0700, Rick Edgecombe wrote: >From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > >Export a function to walk down the TDP without modifying it. > >Future changes will support pre-populating TDX private memory. In order to >implement this KVM will need to check if a given GFN is already >pre-populated in the mirrored EPT, and verify the populated private memory >PFN matches the current one.[1] > >There is already a TDP MMU walker, kvm_tdp_mmu_get_walk() for use within >the KVM MMU that almost does what is required. However, to make sense of >the results, MMU internal PTE helpers are needed. Refactor the code to >provide a helper that can be used outside of the KVM MMU code. > >Refactoring the KVM page fault handler to support this lookup usage was >also considered, but it was an awkward fit. > >Link: https://lore.kernel.org/kvm/ZfBkle1eZFfjPI8l@xxxxxxxxxx/ [1] >Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> >Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx> >--- >This helper will be used in the future change that implements >KVM_TDX_INIT_MEM_REGION. Please refer to the following commit for the >usage: >https://github.com/intel/tdx/commit/2832c6d87a4e6a46828b193173550e80b31240d4 > >TDX MMU Part 1: > - New patch >--- > arch/x86/kvm/mmu.h | 3 +++ > arch/x86/kvm/mmu/tdp_mmu.c | 37 +++++++++++++++++++++++++++++++++---- > 2 files changed, 36 insertions(+), 4 deletions(-) > >diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h >index dc80e72e4848..3c7a88400cbb 100644 >--- a/arch/x86/kvm/mmu.h >+++ b/arch/x86/kvm/mmu.h >@@ -275,6 +275,9 @@ extern bool tdp_mmu_enabled; > #define tdp_mmu_enabled false > #endif > >+int kvm_tdp_mmu_get_walk_private_pfn(struct kvm_vcpu *vcpu, u64 gpa, >+ kvm_pfn_t *pfn); >+ > static inline bool kvm_memslots_have_rmaps(struct kvm *kvm) > { > return !tdp_mmu_enabled || kvm_shadow_root_allocated(kvm); >diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c >index 1259dd63defc..1086e3b2aa5c 100644 >--- a/arch/x86/kvm/mmu/tdp_mmu.c >+++ b/arch/x86/kvm/mmu/tdp_mmu.c >@@ -1772,16 +1772,14 @@ bool kvm_tdp_mmu_write_protect_gfn(struct kvm *kvm, > * > * Must be called between kvm_tdp_mmu_walk_lockless_{begin,end}. > */ >-int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, >- int *root_level) >+static int __kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, >+ bool is_private) is_private isn't used. > { > struct tdp_iter iter; > struct kvm_mmu *mmu = vcpu->arch.mmu; > gfn_t gfn = addr >> PAGE_SHIFT; > int leaf = -1; > >- *root_level = vcpu->arch.mmu->root_role.level; >- > tdp_mmu_for_each_pte(iter, mmu, gfn, gfn + 1) { > leaf = iter.level; > sptes[leaf] = iter.old_spte; >@@ -1790,6 +1788,37 @@ int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, > return leaf; > } > >+int kvm_tdp_mmu_get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, >+ int *root_level) >+{ >+ *root_level = vcpu->arch.mmu->root_role.level; >+ >+ return __kvm_tdp_mmu_get_walk(vcpu, addr, sptes, false); >+} >+ >+int kvm_tdp_mmu_get_walk_private_pfn(struct kvm_vcpu *vcpu, u64 gpa, >+ kvm_pfn_t *pfn) private_pfn probably is a misnomer. shared/private is an attribute of GPA rather than pfn. Since the function is to get pfn from gpa, how about kvm_tdp_mmu_gpa_to_pfn()? And the function is limited to handle private gpa only. It is an artificial limitation we can get rid of easily. e.g., by making the function take "is_private" boolean and relay it to __kvm_tdp_mmu_get_walk(). I know TDX just calls the function to convert private gpa but having a generic API can accommodate future use cases (e.g., get hpa from shared gpa) w/o the need of refactoring. >+{ >+ u64 sptes[PT64_ROOT_MAX_LEVEL + 1], spte; >+ int leaf; >+ >+ lockdep_assert_held(&vcpu->kvm->mmu_lock); >+ >+ rcu_read_lock(); >+ leaf = __kvm_tdp_mmu_get_walk(vcpu, gpa, sptes, true); >+ rcu_read_unlock(); >+ if (leaf < 0) >+ return -ENOENT; >+ >+ spte = sptes[leaf]; >+ if (!(is_shadow_present_pte(spte) && is_last_spte(spte, leaf))) >+ return -ENOENT; >+ >+ *pfn = spte_to_pfn(spte); >+ return leaf; >+} >+EXPORT_SYMBOL_GPL(kvm_tdp_mmu_get_walk_private_pfn); >+ > /* > * Returns the last level spte pointer of the shadow page walk for the given > * gpa, and sets *spte to the spte value. This spte may be non-preset. If no >-- >2.34.1 > >
