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

Commit 26778aaa134a ("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: 26778aaa134a ("KVM: arm64: Commit pending PC adjustemnts before returning to userspace")
Signed-off-by: Zenghui Yu <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Cc: [email protected] # 5.11
(cherry picked from commit e3e880bb1518eb10a4b4bb4344ed614d6856f190)
Signed-off-by: Will Deacon <[email protected]>
Bug: 190594147
Change-Id: I9a8dd5cebd950a578fb6fbde1d302474b6dffdd4

Author: Zenghui Yu

arch/arm64/kvm/arm.c

@@ -727,11 +727,13 @@ 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;
@@ -904,6 +906,7 @@ 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