Hi Aneesh
On 28/04/2025 12:57, Aneesh Kumar K.V (Arm) wrote:
When KVM_RUN fails with EINTR or EAGAIN, we should retry the ioctl
without checking kvm_run->exit_reason. These errors don't indicate a
valid VM exit, hence exit_reason may contain stale or undefined values.
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@xxxxxxxxxx>
---
include/kvm/kvm-cpu.h | 2 +-
kvm-cpu.c | 17 ++++++++++++-----
2 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/include/kvm/kvm-cpu.h b/include/kvm/kvm-cpu.h
index 8f76f8a1123a..72cbb86e6cef 100644
--- a/include/kvm/kvm-cpu.h
+++ b/include/kvm/kvm-cpu.h
@@ -16,7 +16,7 @@ void kvm_cpu__delete(struct kvm_cpu *vcpu);
void kvm_cpu__reset_vcpu(struct kvm_cpu *vcpu);
void kvm_cpu__setup_cpuid(struct kvm_cpu *vcpu);
void kvm_cpu__enable_singlestep(struct kvm_cpu *vcpu);
-void kvm_cpu__run(struct kvm_cpu *vcpu);
+int kvm_cpu__run(struct kvm_cpu *vcpu);
int kvm_cpu__start(struct kvm_cpu *cpu);
bool kvm_cpu__handle_exit(struct kvm_cpu *vcpu);
int kvm_cpu__get_endianness(struct kvm_cpu *vcpu);
diff --git a/kvm-cpu.c b/kvm-cpu.c
index 40041a22b3fe..7abbdcebf075 100644
--- a/kvm-cpu.c
+++ b/kvm-cpu.c
@@ -35,27 +35,32 @@ void kvm_cpu__enable_singlestep(struct kvm_cpu *vcpu)
pr_warning("KVM_SET_GUEST_DEBUG failed");
}
-void kvm_cpu__run(struct kvm_cpu *vcpu)
+/*
+ * return value -1 if we need to call the kvm_cpu__run again without checking
+ * exit_reason. return value 0 results in taking action based on exit_reason.
+ */
minor nit: Should we make the return value meaningful, say -EAGAIN
instead of -1 ?
+int kvm_cpu__run(struct kvm_cpu *vcpu)
{
int err;
if (!vcpu->is_running)
- return;
+ return -1;
err = ioctl(vcpu->vcpu_fd, KVM_RUN, 0);
if (err < 0) {
switch (errno) {
case EINTR:
case EAGAIN:
- return;
+ return -1;
case EFAULT:
if (vcpu->kvm_run->exit_reason == KVM_EXIT_MEMORY_FAULT)
- return;
+ return 0;
/* fallthrough */
default:
die_perror("KVM_RUN failed");
}
}
+ return 0;
}
static void kvm_cpu_signal_handler(int signum)
@@ -179,7 +184,9 @@ int kvm_cpu__start(struct kvm_cpu *cpu)
if (cpu->task)
kvm_cpu__run_task(cpu);
- kvm_cpu__run(cpu);
+ if (kvm_cpu__run(cpu) == -1)
and this could be :
if (kvm_cpu__run(cpu) == -EAGAIN)
+ /* retry without an exit_reason check */
+ continue;
switch (cpu->kvm_run->exit_reason) {
case KVM_EXIT_UNKNOWN:
Suzuki
