* [PATCH 2/2] target/loongarch: Enable PV TLB flush advertisement to the guest
2026-06-15 8:52 [PATCH 0/2] target/loongarch: PV TLB flush advertisement Tao Cui
2026-06-15 8:52 ` [PATCH 1/2] linux-headers: Add LoongArch PV TLB flush definitions Tao Cui
@ 2026-06-15 8:52 ` Tao Cui
2026-06-15 9:20 ` [PATCH 0/2] target/loongarch: PV TLB flush advertisement gaosong
2 siblings, 0 replies; 4+ messages in thread
From: Tao Cui @ 2026-06-15 8:52 UTC (permalink / raw)
To: qemu-devel
Cc: Song Gao, Paolo Bonzini, Michael S . Tsirkin, Cornelia Huck, kvm,
Tao Cui
From: Tao Cui <cuitao@kylinos.cn>
Probe the KVM_LOONGARCH_VM_FEAT_PV_TLB_FLUSH VM-level capability and, when
the host supports it, advertise KVM_FEATURE_PV_TLB_FLUSH to the guest by
including it in the CPUCFG_KVM_FEATURE feature mask handed to the kernel.
This mirrors the existing PV IPI / steal-time enablement. A new
kvm-pv-tlb-flush CPU property (on/off/auto, default auto) lets users
disable the feature, e.g. when migrating to a host that lacks it.
The feature is only advertised when the host actually supports it, so a
guest never observes KVM_FEATURE_PV_TLB_FLUSH on a host that cannot
service PV TLB flush requests (which would otherwise lead to stale TLBs).
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
---
target/loongarch/cpu.h | 2 ++
target/loongarch/kvm/kvm.c | 38 +++++++++++++++++++++++++++
target/loongarch/loongarch-qmp-cmds.c | 4 +--
3 files changed, 42 insertions(+), 2 deletions(-)
diff --git a/target/loongarch/cpu.h b/target/loongarch/cpu.h
index ad30c73167..94e8f176f4 100644
--- a/target/loongarch/cpu.h
+++ b/target/loongarch/cpu.h
@@ -300,6 +300,7 @@ enum loongarch_features {
LOONGARCH_FEATURE_PMU,
LOONGARCH_FEATURE_PV_IPI,
LOONGARCH_FEATURE_STEALTIME,
+ LOONGARCH_FEATURE_PV_TLB_FLUSH,
LOONGARCH_FEATURE_PTW,
};
@@ -447,6 +448,7 @@ struct ArchCPU {
OnOffAuto msgint;
OnOffAuto kvm_pv_ipi;
OnOffAuto kvm_steal_time;
+ OnOffAuto kvm_pv_tlb_flush;
int32_t socket_id; /* socket-id of this CPU */
int32_t core_id; /* core-id of this CPU */
int32_t thread_id; /* thread-id of this CPU */
diff --git a/target/loongarch/kvm/kvm.c b/target/loongarch/kvm/kvm.c
index d6539c12ac..f91c388bf3 100644
--- a/target/loongarch/kvm/kvm.c
+++ b/target/loongarch/kvm/kvm.c
@@ -981,6 +981,12 @@ static bool kvm_feature_supported(CPUState *cs, enum loongarch_features feature)
ret = kvm_vm_ioctl(kvm_state, KVM_HAS_DEVICE_ATTR, &attr);
return (ret == 0);
+ case LOONGARCH_FEATURE_PV_TLB_FLUSH:
+ attr.group = KVM_LOONGARCH_VM_FEAT_CTRL;
+ attr.attr = KVM_LOONGARCH_VM_FEAT_PV_TLB_FLUSH;
+ ret = kvm_vm_ioctl(kvm_state, KVM_HAS_DEVICE_ATTR, &attr);
+ return (ret == 0);
+
case LOONGARCH_FEATURE_PTW:
attr.group = KVM_LOONGARCH_VM_FEAT_CTRL;
attr.attr = KVM_LOONGARCH_VM_FEAT_PTW;
@@ -1150,6 +1156,20 @@ static int kvm_cpu_check_pv_features(CPUState *cs, Error **errp)
env->pv_features |= BIT(KVM_FEATURE_STEAL_TIME);
}
+ kvm_supported = kvm_feature_supported(cs, LOONGARCH_FEATURE_PV_TLB_FLUSH);
+ if (cpu->kvm_pv_tlb_flush == ON_OFF_AUTO_ON) {
+ if (!kvm_supported) {
+ error_setg(errp, "'pv_tlb_flush' not supported by KVM host");
+ return -ENOTSUP;
+ }
+ } else if (cpu->kvm_pv_tlb_flush != ON_OFF_AUTO_AUTO) {
+ kvm_supported = false;
+ }
+
+ if (kvm_supported) {
+ env->pv_features |= BIT(KVM_FEATURE_PV_TLB_FLUSH);
+ }
+
if (object_dynamic_cast(OBJECT(ms), TYPE_LOONGARCH_VIRT_MACHINE)) {
LoongArchVirtMachineState *lvms = LOONGARCH_VIRT_MACHINE(ms);
@@ -1266,6 +1286,18 @@ static void kvm_steal_time_set(Object *obj, bool value, Error **errp)
cpu->kvm_steal_time = value ? ON_OFF_AUTO_ON : ON_OFF_AUTO_OFF;
}
+static bool kvm_pv_tlb_flush_get(Object *obj, Error **errp)
+{
+ return LOONGARCH_CPU(obj)->kvm_pv_tlb_flush != ON_OFF_AUTO_OFF;
+}
+
+static void kvm_pv_tlb_flush_set(Object *obj, bool value, Error **errp)
+{
+ LoongArchCPU *cpu = LOONGARCH_CPU(obj);
+
+ cpu->kvm_pv_tlb_flush = value ? ON_OFF_AUTO_ON : ON_OFF_AUTO_OFF;
+}
+
void kvm_loongarch_cpu_post_init(LoongArchCPU *cpu)
{
cpu->lbt = ON_OFF_AUTO_AUTO;
@@ -1291,6 +1323,12 @@ void kvm_loongarch_cpu_post_init(LoongArchCPU *cpu)
kvm_steal_time_set);
object_property_set_description(OBJECT(cpu), "kvm-steal-time",
"Set off to disable KVM steal time.");
+
+ cpu->kvm_pv_tlb_flush = ON_OFF_AUTO_AUTO;
+ object_property_add_bool(OBJECT(cpu), "kvm-pv-tlb-flush",
+ kvm_pv_tlb_flush_get, kvm_pv_tlb_flush_set);
+ object_property_set_description(OBJECT(cpu), "kvm-pv-tlb-flush",
+ "Set off to disable KVM PV TLB flush.");
}
int kvm_arch_destroy_vcpu(CPUState *cs)
diff --git a/target/loongarch/loongarch-qmp-cmds.c b/target/loongarch/loongarch-qmp-cmds.c
index f053f22bb8..5f372d85a9 100644
--- a/target/loongarch/loongarch-qmp-cmds.c
+++ b/target/loongarch/loongarch-qmp-cmds.c
@@ -41,8 +41,8 @@ CpuDefinitionInfoList *qmp_query_cpu_definitions(Error **errp)
}
static const char *cpu_model_advertised_features[] = {
- "lsx", "lasx", "lbt", "pmu", "kvm-pv-ipi", "kvm-steal-time", "msgint",
- "ptw", NULL
+ "lsx", "lasx", "lbt", "pmu", "kvm-pv-ipi", "kvm-steal-time",
+ "kvm-pv-tlb-flush", "msgint", "ptw", NULL
};
CpuModelExpansionInfo *qmp_query_cpu_model_expansion(CpuModelExpansionType type,
--
2.43.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH 0/2] target/loongarch: PV TLB flush advertisement
2026-06-15 8:52 [PATCH 0/2] target/loongarch: PV TLB flush advertisement Tao Cui
2026-06-15 8:52 ` [PATCH 1/2] linux-headers: Add LoongArch PV TLB flush definitions Tao Cui
2026-06-15 8:52 ` [PATCH 2/2] target/loongarch: Enable PV TLB flush advertisement to the guest Tao Cui
@ 2026-06-15 9:20 ` gaosong
2 siblings, 0 replies; 4+ messages in thread
From: gaosong @ 2026-06-15 9:20 UTC (permalink / raw)
To: Tao Cui, qemu-devel
Cc: Paolo Bonzini, Michael S . Tsirkin, Cornelia Huck, kvm, Tao Cui,
bibo mao
在 2026/6/15 下午4:52, Tao Cui 写道:
> From: Tao Cui <cuitao@kylinos.cn>
>
> Advertise the LoongArch paravirtual TLB flush feature (KVM_FEATURE_PV_TLB_FLUSH)
> to the guest when the host KVM supports it. This pairs with the corresponding
> KVM/guest-kernel PV TLB flush series posted to the kernel.
>
> Patch 1 syncs the UAPI definitions into linux-headers.
Hi, you should use scripts/update-linux-headers.sh to update the
linux-headers.
Thanks.
Song Gao
> Patch 2 adds the probe, the CPUCFG feature advertisement, and a
> kvm-pv-tlb-flush CPU property (on/off/auto, default auto).
>
> The feature is only advertised when the host actually supports it, so a
> guest never observes KVM_FEATURE_PV_TLB_FLUSH on a host that cannot
> service PV TLB flush requests.
> Tao Cui (2):
> linux-headers: Add LoongArch PV TLB flush definitions
> target/loongarch: Enable PV TLB flush advertisement to the guest
>
> linux-headers/asm-loongarch/kvm.h | 1 +
> linux-headers/asm-loongarch/kvm_para.h | 1 +
> target/loongarch/cpu.h | 2 ++
> target/loongarch/kvm/kvm.c | 38 ++++++++++++++++++++++++++
> target/loongarch/loongarch-qmp-cmds.c | 4 +--
> 5 files changed, 44 insertions(+), 2 deletions(-)
>
^ permalink raw reply [flat|nested] 4+ messages in thread