[PATCH kvmtool v3 1/3] cpu: vmexit: Handle KVM_EXIT_MEMORY_FAULT in KVM_RUN ioctl return

["Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>]

Linux kernel documentation states:

"Note! KVM_EXIT_MEMORY_FAULT is unique among all KVM exit reasons in
that it accompanies a return code of '-1', not '0'! errno will always be
set to EFAULT or EHWPOISON when KVM exits with KVM_EXIT_MEMORY_FAULT,
userspace should assume kvm_run.exit_reason is stale/undefined for all
other error numbers." "

Update KVM_RUN ioctl error handling to correctly handle
KVM_EXIT_MEMORY_FAULT. This enables the memory fault exit handlers in
the kernel to return -EFAULT as the return value. VMM support is
still required to handle these memory fault exits, but that is not
included in this change

Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 kvm-cpu.c | 15 +++++++++++++--
 kvm.c     |  1 +
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/kvm-cpu.c b/kvm-cpu.c
index 7362f2e99261..40041a22b3fe 100644
--- a/kvm-cpu.c
+++ b/kvm-cpu.c
@@ -43,8 +43,19 @@ void kvm_cpu__run(struct kvm_cpu *vcpu)
 		return;
 
 	err = ioctl(vcpu->vcpu_fd, KVM_RUN, 0);
-	if (err < 0 && (errno != EINTR && errno != EAGAIN))
-		die_perror("KVM_RUN failed");
+	if (err < 0) {
+		switch (errno) {
+		case EINTR:
+		case EAGAIN:
+			return;
+		case EFAULT:
+			if (vcpu->kvm_run->exit_reason == KVM_EXIT_MEMORY_FAULT)
+				return;
+			/* fallthrough */
+		default:
+			die_perror("KVM_RUN failed");
+		}
+	}
 }
 
 static void kvm_cpu_signal_handler(int signum)
diff --git a/kvm.c b/kvm.c
index 07089cf1b332..b6375a114d11 100644
--- a/kvm.c
+++ b/kvm.c
@@ -55,6 +55,7 @@ const char *kvm_exit_reasons[] = {
 #ifdef CONFIG_PPC64
 	DEFINE_KVM_EXIT_REASON(KVM_EXIT_PAPR_HCALL),
 #endif
+	DEFINE_KVM_EXIT_REASON(KVM_EXIT_MEMORY_FAULT),
 };
 
 static int pause_event;
-- 
2.43.0