This addresses the following crash when running Linux v5.8 with kernel-irqchip=off: qemu-system-x86_64: error: failed to set MSR 0x4b564d02 to 0x0 qemu-system-x86_64: ../target/i386/kvm.c:2714: kvm_buf_set_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed. There is a kernel-side fix for the issue too (kernel commit d831de177217 "KVM: x86: always allow writing '0' to MSR_KVM_ASYNC_PF_EN"), but it's nice to simply not trigger the bug if running an older kernel. Fixes: https://bugs.launchpad.net/bugs/1896263 Signed-off-by: Eduardo Habkost <ehabkost@xxxxxxxxxx> --- target/i386/kvm.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/target/i386/kvm.c b/target/i386/kvm.c index 9efb07e7c83..1492f41349f 100644 --- a/target/i386/kvm.c +++ b/target/i386/kvm.c @@ -2818,7 +2818,12 @@ static int kvm_put_msrs(X86CPU *cpu, int level) kvm_msr_entry_add(cpu, MSR_IA32_TSC, env->tsc); kvm_msr_entry_add(cpu, MSR_KVM_SYSTEM_TIME, env->system_time_msr); kvm_msr_entry_add(cpu, MSR_KVM_WALL_CLOCK, env->wall_clock_msr); - if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_ASYNC_PF)) { + /* + * Some kernel versions (v5.8) won't let MSR_KVM_ASYNC_PF_EN to be set + * at all if kernel-irqchip=off, so don't try to set it in that case. + */ + if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_ASYNC_PF) && + kvm_irqchip_in_kernel()) { kvm_msr_entry_add(cpu, MSR_KVM_ASYNC_PF_EN, env->async_pf_en_msr); } if (env->features[FEAT_KVM] & (1 << KVM_FEATURE_PV_EOI)) { -- 2.26.2
