On Thu, Jun 12, 2025 at 7:29 AM Xiaoyao Li <xiaoyao.li@xxxxxxxxx> wrote: > > On 6/12/2025 12:49 PM, Paolo Bonzini wrote: > > Only let userspace pass the same addresses that were used in KVM_SET_USER_MEMORY_REGION > > (or KVM_SET_USER_MEMORY_REGION2); gpas in the the upper half of the address space > > are an implementation detail of TDX and KVM. > > > > Extracted from a patch by Sean Christopherson <seanjc@xxxxxxxxxx>. > > > > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> > > --- > > arch/x86/kvm/mmu/mmu.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > > index a4040578b537..4e06e2e89a8f 100644 > > --- a/arch/x86/kvm/mmu/mmu.c > > +++ b/arch/x86/kvm/mmu/mmu.c > > @@ -4903,6 +4903,9 @@ long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu, > > if (!vcpu->kvm->arch.pre_fault_allowed) > > return -EOPNOTSUPP; > > > > + if (kvm_is_gfn_alias(vcpu->kvm, gpa_to_gfn(range->gpa))) > > + return -EINVAL; > > Do we need to worry about the case (range->gpa + range->size) becomes alias? No, because the function only processes a single page and everything in the non-aliased part of the address space *can* be prefaulted. KVM's generic kvm_vcpu_pre_fault_memory() call will see the EINVAL on a later invocation and will stop processing the part of the request that is has the shared/direct bit set. Paolo > > > /* > > * reload is efficient when called repeatedly, so we can do it on > > * every iteration. >
