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KVM: arm64: nv: Re-translate VNCR before injecting abort

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KVM faults in the VNCR page with FOLL_WRITE whenever the guest aborts
for a write, similar to how a regular stage-2 mapping is handled. It is
entirely possible that the guest reads from the VNCR before writing to
it, in which case the PFN could only be read-only.

Invalidate the VNCR TLB and re-fetch the translation upon taking a VNCR
abort, allowing the host mapping to be faulted in for write the second
time around. Interestingly enough, this also satisfies the ordering
requirements of FEAT_ETS2/3 between descriptor updates and MMU faults.

Cc: stable@vger.kernel.org
Fixes: 2a359e0725 ("KVM: arm64: nv: Handle mapping of VNCR_EL2 at EL2")
Reported-by: Sashiko <sashiko-bot@kernel.org>
Signed-off-by: Oliver Upton <oupton@kernel.org>
Link: https://patch.msgid.link/20260618234207.1063941-4-oupton@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Oliver Upton 2026-06-18 16:42:04 -07:00 committed by Marc Zyngier
parent 9f3e83345a
commit bb645aa0a4
1 changed files with 44 additions and 71 deletions
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115
arch/arm64/kvm/nested.c
View File

@ -1466,88 +1466,61 @@ static void handle_vncr_perm(struct kvm_vcpu *vcpu)
kvm_inject_nested_sync(vcpu, esr);
}
static bool kvm_vncr_tlb_lookup(struct kvm_vcpu *vcpu)
{
struct vncr_tlb *vt = vcpu->arch.vncr_tlb;
lockdep_assert_held_read(&vcpu->kvm->mmu_lock);
if (!vt->valid)
return false;
if (read_vncr_el2(vcpu) != vt->gva)
return false;
if (vt->wr.nG)
return get_asid_by_regime(vcpu, TR_EL20) == vt->wr.asid;
return true;
}
int kvm_handle_vncr_abort(struct kvm_vcpu *vcpu)
{
struct vncr_tlb *vt = vcpu->arch.vncr_tlb;
u64 esr = kvm_vcpu_get_esr(vcpu);
bool is_gmem = false;
bool perm;
int ret;
WARN_ON_ONCE(!(esr & ESR_ELx_VNCR));
if (kvm_vcpu_abt_issea(vcpu))
return kvm_handle_guest_sea(vcpu);
if (esr_fsc_is_permission_fault(esr)) {
handle_vncr_perm(vcpu);
} else if (esr_fsc_is_translation_fault(esr)) {
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, &is_gmem);
else
ret = -EPERM;
switch (ret) {
case -EAGAIN:
/* 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:
/*
* Translation failed, inject the corresponding
* exception back to EL2.
*/
esr &= ~ESR_ELx_FSC;
esr |= FIELD_PREP(ESR_ELx_FSC, vt->wr.fst);
kvm_inject_nested_sync(vcpu, esr);
break;
case -EPERM:
/* Hack to deal with POE until we get kernel support */
handle_vncr_perm(vcpu);
break;
case 0:
break;
}
} else {
if (!esr_fsc_is_translation_fault(esr) && !esr_fsc_is_permission_fault(esr)) {
WARN_ONCE(1, "Unhandled VNCR abort, ESR=%llx\n", esr);
return 1;
}
ret = kvm_translate_vncr(vcpu, &is_gmem);
switch (ret) {
case -EAGAIN:
/* Let's try again... */
return 1;
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:
/*
* Translation failed, inject the corresponding
* exception back to EL2.
*/
esr &= ~ESR_ELx_FSC;
esr |= FIELD_PREP(ESR_ELx_FSC, vt->wr.fst);
kvm_inject_nested_sync(vcpu, esr);
break;
case 0:
perm = kvm_is_write_fault(vcpu) ? vt->wr.pw && vt->hpa_writable : vt->wr.pr;
if (!perm)
handle_vncr_perm(vcpu);
break;
}
return 1;