Consider a system with 8 harts, where each hart supports 5
Guest Interrupt Files (GIFs), yielding 40 total GIFs.
If we launch a QEMU guest with over 5 vCPUs using
"-M virt,aia='aplic-imsic' -accel kvm,riscv-aia=hwaccel" – which
relies solely on VS-files (not SW-files) for higher performance – the
guest requires more than 5 GIFs. However, the current Linux scheduler
lacks GIF awareness, potentially scheduling >5 vCPUs to a single hart.
This triggers VS-file allocation failure, and since no handler exists
for this error, the QEMU guest becomes corrupted.
To address this, we introduce this simple handler by rescheduling vCPU
to alternative harts when VS-file allocation fails on the current hart.
Signed-off-by: BillXiang <xiangwench...@lanxincomputing.com>
---
target/riscv/kvm/kvm-cpu.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c
index 5c19062c19..7cf258604f 100644
--- a/target/riscv/kvm/kvm-cpu.c
+++ b/target/riscv/kvm/kvm-cpu.c
@@ -1706,6 +1706,9 @@ static bool kvm_riscv_handle_debug(CPUState *cs)
int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
{
int ret = 0;
+ uint64_t code;
+ cpu_set_t set;
+ long cpus;
switch (run->exit_reason) {
case KVM_EXIT_RISCV_SBI:
ret = kvm_riscv_handle_sbi(cs, run);
@@ -1718,6 +1721,18 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run
*run)
ret = EXCP_DEBUG;
}
break;
+ case KVM_EXIT_FAIL_ENTRY:
+ code = run->fail_entry.hardware_entry_failure_reason;
+ if (code == CSR_HSTATUS) {
+ // Schedule vcpu to next hart upon VS-file
+ // allocation failure on current hart.
+ cpus = sysconf(_SC_NPROCESSORS_ONLN);
+ CPU_ZERO(&set);
+ CPU_SET((run->fail_entry.cpu+1)%cpus, &set);
+ ret = sched_setaffinity(0, sizeof(set), &set);
+ break;
+ }
+ /* FALLTHRU */
default:
qemu_log_mask(LOG_UNIMP, "%s: un-handled exit reason %d\n",
__func__, run->exit_reason);
--
2.46.2.windows.1
