KVM: arm64: Resolve all pending PC updates before immediate exit

Commit 26e0aabb38a6 ("KVM: arm64: Commit pending PC adjustemnts before
returning to userspace") fixed the PC updating issue by forcing an explicit
synchronisation of the exception state on vcpu exit to userspace.

However, we forgot to take into account the case where immediate_exit is
set by userspace and KVM_RUN will exit immediately. Fix it by resolving all
pending PC updates before returning to userspace.

Since __kvm_adjust_pc() relies on a loaded vcpu context, I moved the
immediate_exit checking right after vcpu_load(). We will get some overhead
if immediate_exit is true (which should hopefully be rare).

Fixes: 26e0aabb38a6 ("KVM: arm64: Commit pending PC adjustemnts before returning to userspace")
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210526141831.1662-1-yuzenghui@huawei.com
Cc: stable@vger.kernel.org # 5.11

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 1126eae27400051adb2ffbf8a3cf2355170eb5e4..e720148232a06c887c3035f3a4f790d235ec6744 100644 (file)
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -720,11 +720,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
                        return ret;
        }
 
-       if (run->immediate_exit)
-               return -EINTR;
-
        vcpu_load(vcpu);
 
+       if (run->immediate_exit) {
+               ret = -EINTR;
+               goto out;
+       }
+
        kvm_sigset_activate(vcpu);
 
        ret = 1;
@@ -897,6 +899,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 
        kvm_sigset_deactivate(vcpu);
 
+out:
        /*
         * In the unlikely event that we are returning to userspace
         * with pending exceptions or PC adjustment, commit these