Re: [PATCH 4/6] LoongArch: KVM: implement vmid updating logic

[Bibo Mao <maobibo@loongson.cn>]

On 2026/8/2 下午10:13, Huacai Chen wrote:
> Hi, BIbo,
> 
> On Mon, Jul 27, 2026 at 3:30 PM Bibo Mao <maobibo@loongson.cn> wrote:
>>
>> For every physical CPU, there is one vmid calculation method. For
>> vCPUs on the same VM, vmid is the same. However for vCPUs on
>> different VM, vmid is different. When vCPU is scheduled on the
>> physical CPU, it checked vmid of this VM and the global cached
>> vmid, and judge whether it is valid or not.
> I think Patch#2/3/4 can be folded into one.
will merge patch 2/3/4 together.

Regards
Bibo Mao
> 
> 
> Huacai
> 
>>
>> Signed-off-by: Bibo Mao <maobibo@loongson.cn>
>> ---
>>   arch/loongarch/include/asm/kvm_host.h |  2 ++
>>   arch/loongarch/kvm/main.c             | 42 ++++++++++++++++++++++++++-
>>   2 files changed, 43 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
>> index e93307cbe740..a01623c42c7a 100644
>> --- a/arch/loongarch/include/asm/kvm_host.h
>> +++ b/arch/loongarch/include/asm/kvm_host.h
>> @@ -79,6 +79,7 @@ struct kvm_arch_memory_slot {
>>   #define HOST_MAX_PMNUM                 16
>>   struct kvm_context {
>>          unsigned long vpid_cache;
>> +       unsigned long vmid_cache;
>>          struct kvm_vcpu *last_vcpu;
>>          /* Host PMU CSR */
>>          u64 perf_ctrl[HOST_MAX_PMNUM];
>> @@ -132,6 +133,7 @@ struct kvm_arch {
>>          unsigned long kvm_features;
>>
>>          s64 time_offset;
>> +       unsigned long vmid[NR_CPUS];
>>          struct kvm_context __percpu *vmcs;
>>          struct loongarch_ipi *ipi;
>>          struct loongarch_dmsintc *dmsintc;
>> diff --git a/arch/loongarch/kvm/main.c b/arch/loongarch/kvm/main.c
>> index 3df46e02594f..7b3661da8958 100644
>> --- a/arch/loongarch/kvm/main.c
>> +++ b/arch/loongarch/kvm/main.c
>> @@ -281,9 +281,33 @@ static void kvm_check_vcpuid(struct kvm_vcpu *vcpu)
>>          }
>>   }
>>
>> -static void kvm_check_vmid(struct kvm_vcpu *vcpu)
>> +static void kvm_update_vmid(struct kvm_vcpu *vcpu, int cpu)
>>   {
>>          unsigned long vmid;
>> +       struct kvm_context *context;
>> +
>> +       context = per_cpu_ptr(vcpu->kvm->arch.vmcs, cpu);
>> +       vmid = context->vmid_cache + 1;
>> +       if (!(vmid & vpid_mask)) {
>> +               /* finish round of vmid loop */
>> +               if (unlikely(!vmid))
>> +                       vmid = vpid_mask + 1;
>> +
>> +               ++vmid; /* vmid 0 reserved for root */
>> +
>> +               /* start new vmid cycle */
>> +               kvm_flush_tlb_all_stage2();
>> +       }
>> +
>> +       context->vmid_cache = vmid;
>> +       vcpu->kvm->arch.vmid[cpu] = vmid;
>> +}
>> +
>> +static void kvm_check_vmid(struct kvm_vcpu *vcpu)
>> +{
>> +       int cpu;
>> +       unsigned long ver, old, vmid;
>> +       struct kvm_context *context;
>>
>>          /* On some machines like 3A5000, vmid needs the same with vpid */
>>          if (!cpu_has_guestid) {
>> @@ -295,6 +319,21 @@ static void kvm_check_vmid(struct kvm_vcpu *vcpu)
>>
>>                  return;
>>          }
>> +
>> +       cpu = smp_processor_id();
>> +       context = per_cpu_ptr(vcpu->kvm->arch.vmcs, cpu);
>> +
>> +       /*
>> +        * Check if our vmid is of an older version
>> +        */
>> +       ver = vcpu->kvm->arch.vmid[cpu] & ~vpid_mask;
>> +       old = context->vmid_cache & ~vpid_mask;
>> +       if (ver != old) {
>> +               kvm_update_vmid(vcpu, cpu);
>> +               kvm_clear_request(KVM_REQ_TLB_FLUSH_GPA, vcpu);
>> +       }
>> +
>> +       vcpu->arch.vmid = vcpu->kvm->arch.vmid[cpu] & vpid_mask;
>>   }
>>
>>   void kvm_check_vpid(struct kvm_vcpu *vcpu)
>> @@ -400,6 +439,7 @@ static int kvm_loongarch_env_init(void)
>>          for_each_possible_cpu(cpu) {
>>                  context = per_cpu_ptr(vmcs, cpu);
>>                  context->vpid_cache = vpid_mask + 1;
>> +               context->vmid_cache = vpid_mask + 1;
>>                  context->last_vcpu = NULL;
>>          }
>>
>> --
>> 2.39.3
>>