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KVM: arm64: nv: Handle VNCR_EL2-triggered faults backed by guest_memfd

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Handle faults for memslots backed by guest_memfd in arm64 nested
virtualization triggered by VNCR_EL2.

* Introduce is_gmem output parameter to kvm_translate_vncr(), indicating
  whether the faulted memory slot is backed by guest_memfd.

* Dispatch faults backed by guest_memfd to kvm_gmem_get_pfn().

* Update kvm_handle_vncr_abort() to handle potential guest_memfd errors.
  Some of the guest_memfd errors need to be handled by userspace instead
  of attempting to (implicitly) retry by returning to the guest.

Suggested-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20250729225455.670324-20-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Fuad Tabba 2025-07-29 15:54:50 -07:00 • committed by Paolo Bonzini
parent a7b57e0995
commit f4e740309e
1 changed files with 35 additions and 6 deletions
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41
arch/arm64/kvm/nested.c
View file

@ -1172,8 +1172,9 @@ static u64 read_vncr_el2(struct kvm_vcpu *vcpu)
return (u64)sign_extend64(__vcpu_sys_reg(vcpu, VNCR_EL2), 48);
}
static int kvm_translate_vncr(struct kvm_vcpu *vcpu)
static int kvm_translate_vncr(struct kvm_vcpu *vcpu, bool *is_gmem)
{
struct kvm_memory_slot *memslot;
bool write_fault, writable;
unsigned long mmu_seq;
struct vncr_tlb *vt;
@ -1216,10 +1217,25 @@ static int kvm_translate_vncr(struct kvm_vcpu *vcpu)
smp_rmb();
gfn = vt->wr.pa >> PAGE_SHIFT;
pfn = kvm_faultin_pfn(vcpu, gfn, write_fault, &writable, &page);
if (is_error_noslot_pfn(pfn) || (write_fault && !writable))
memslot = gfn_to_memslot(vcpu->kvm, gfn);
if (!memslot)
return -EFAULT;
*is_gmem = kvm_slot_has_gmem(memslot);
if (!*is_gmem) {
pfn = __kvm_faultin_pfn(memslot, gfn, write_fault ? FOLL_WRITE : 0,
&writable, &page);
if (is_error_noslot_pfn(pfn) || (write_fault && !writable))
return -EFAULT;
} else {
ret = kvm_gmem_get_pfn(vcpu->kvm, memslot, gfn, &pfn, &page, NULL);
if (ret) {
kvm_prepare_memory_fault_exit(vcpu, vt->wr.pa, PAGE_SIZE,
write_fault, false, false);
return ret;
}
}
scoped_guard(write_lock, &vcpu->kvm->mmu_lock) {
if (mmu_invalidate_retry(vcpu->kvm, mmu_seq))
return -EAGAIN;
@ -1292,23 +1308,36 @@ int kvm_handle_vncr_abort(struct kvm_vcpu *vcpu)
if (esr_fsc_is_permission_fault(esr)) {
inject_vncr_perm(vcpu);
} else if (esr_fsc_is_translation_fault(esr)) {
bool valid;
bool valid, is_gmem = false;
int ret;
scoped_guard(read_lock, &vcpu->kvm->mmu_lock)
valid = kvm_vncr_tlb_lookup(vcpu);
if (!valid)
ret = kvm_translate_vncr(vcpu);
ret = kvm_translate_vncr(vcpu, &is_gmem);
else
ret = -EPERM;
switch (ret) {
case -EAGAIN:
case -ENOMEM:
/* Let's try again... */
break;
case -ENOMEM:
/*
* For guest_memfd, this indicates that it failed to
* create a folio to back the memory. Inform userspace.
*/
if (is_gmem)
return 0;
/* Otherwise, let's try again... */
break;
case -EFAULT:
case -EIO:
case -EHWPOISON:
if (is_gmem)
return 0;
fallthrough;
case -EINVAL:
case -ENOENT:
case -EACCES: