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KVM: arm64: nv: Respect stage-2 write permssion when setting stage-1 AF

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Naturally, updating the Access Flag in a stage-1 descriptor requires
write permission at stage-2, although this isn't actually enforced in
KVM's software PTW.

Generate a stage-2 permission fault if the stage-1 walk attempts to
update the descriptor and its corresponding stage-2 translation lacks
write permission.

Fixes: bff8aa213d ("KVM: arm64: Implement HW access flag management in stage-1 SW PTW")
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://msgid.link/20260108204230.677172-1-oupton@kernel.org
Signed-off-by: Oliver Upton <oupton@kernel.org>
This commit is contained in:
Oliver Upton 2026-01-08 12:42:30 -08:00
parent 9cb2c20f06
commit 9e27085c33
1 changed files with 6 additions and 2 deletions
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8
arch/arm64/kvm/at.c
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@ -403,6 +403,7 @@ static int walk_s1(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
struct s1_walk_result *wr, u64 va)
{
u64 va_top, va_bottom, baddr, desc, new_desc, ipa;
struct kvm_s2_trans s2_trans = {};
int level, stride, ret;
level = wi->sl;
@ -420,8 +421,6 @@ static int walk_s1(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
ipa = baddr | index;
if (wi->s2) {
struct kvm_s2_trans s2_trans = {};
ret = kvm_walk_nested_s2(vcpu, ipa, &s2_trans);
if (ret) {
fail_s1_walk(wr,
@ -515,6 +514,11 @@ static int walk_s1(struct kvm_vcpu *vcpu, struct s1_walk_info *wi,
new_desc |= PTE_AF;
if (new_desc != desc) {
if (wi->s2 && !kvm_s2_trans_writable(&s2_trans)) {
fail_s1_walk(wr, ESR_ELx_FSC_PERM_L(level), true);
return -EPERM;
}
ret = kvm_swap_s1_desc(vcpu, ipa, desc, new_desc, wi);
if (ret)
return ret;