[PATCH 4/5] KVM: arm64: Restart instruction upon race in __kvm_at_s12()

[Oliver Upton <oupton@kernel.org>]

__kvm_at_s*() are expected to return -EAGAIN if the page table walk
raced with a concurrent update to a page table descriptor, which is
interpreted as a signal to restart the trapping instruction.

While this mostly works, __kvm_at_s12() silently eats the return from
__kvm_at_s1e01() and consumes an uninitialized PAR value. Propagate the
nonzero return instead.

Fixes: 92c6443222ca ("KVM: arm64: Propagate PTW errors up to AT emulation")
Signed-off-by: Oliver Upton <oupton@kernel.org>
---
 arch/arm64/kvm/at.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/at.c b/arch/arm64/kvm/at.c
index 119a603e636e..6cc5892023dd 100644
--- a/arch/arm64/kvm/at.c
+++ b/arch/arm64/kvm/at.c
@@ -1557,7 +1557,10 @@ int __kvm_at_s12(struct kvm_vcpu *vcpu, u32 op, u64 vaddr)
 		return 0;
 	}
 
-	__kvm_at_s1e01(vcpu, op, vaddr);
+	ret = __kvm_at_s1e01(vcpu, op, vaddr);
+	if (ret)
+		return ret;
+
 	par = vcpu_read_sys_reg(vcpu, PAR_EL1);
 	if (par & SYS_PAR_EL1_F)
 		return 0;
-- 
2.47.3