Re: [PATCH 6/6] LoongArch: KVM: Enable separate vmid feature

On 2026/8/2 下午10:14, Huacai Chen wrote:
> Hi, Bibo,
> 
> On Mon, Jul 27, 2026 at 3:31 PM Bibo Mao <[email protected]> wrote:
>>
>> With CSR GTLBC shortname for Guest TLB Control Register, separate vmid
>> feature will be enabled if bit 14 CSR_GTLBC_USEVMID is set. Enable
>> this feature if cpu_has_guestid is true when LVZ is enabled and the LVZ
>> version is 2.
>>
>> Signed-off-by: Bibo Mao <[email protected]>
>> ---
>>   arch/loongarch/include/asm/loongarch.h | 2 ++
>>   arch/loongarch/kernel/cpu-probe.c      | 7 ++++++-
>>   arch/loongarch/kvm/main.c              | 4 +++-
>>   3 files changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
>> index 2a6bc99177d8..4c4249446a61 100644
>> --- a/arch/loongarch/include/asm/loongarch.h
>> +++ b/arch/loongarch/include/asm/loongarch.h
>> @@ -350,6 +350,8 @@
>>   #define  CSR_GTLBC_TGID_WIDTH          8
>>   #define  CSR_GTLBC_TGID_SHIFT_END      (CSR_GTLBC_TGID_SHIFT + CSR_GTLBC_TGID_WIDTH - 1)
>>   #define  CSR_GTLBC_TGID                        (_ULCAST_(0xff) << CSR_GTLBC_TGID_SHIFT)
>> +#define  CSR_GTLBC_USEVMID_SHIFT       14
>> +#define  CSR_GTLBC_USEVMID             (_ULCAST_(0x1) << CSR_GTLBC_USEVMID_SHIFT)
>>   #define  CSR_GTLBC_TOTI_SHIFT          13
>>   #define  CSR_GTLBC_TOTI                        (_ULCAST_(0x1) << CSR_GTLBC_TOTI_SHIFT)
>>   #define  CSR_GTLBC_USETGID_SHIFT       12
>> diff --git a/arch/loongarch/kernel/cpu-probe.c b/arch/loongarch/kernel/cpu-probe.c
>> index 74d31f260dfd..cbf1dafac0a0 100644
>> --- a/arch/loongarch/kernel/cpu-probe.c
>> +++ b/arch/loongarch/kernel/cpu-probe.c
>> @@ -135,7 +135,7 @@ static void set_isa(struct cpuinfo_loongarch *c, unsigned int isa)
>>
>>   static void cpu_probe_common(struct cpuinfo_loongarch *c)
>>   {
>> -       unsigned int config;
>> +       unsigned int config, version;
>>          unsigned long asid_mask;
>>
>>          c->options = LOONGARCH_CPU_CPUCFG | LOONGARCH_CPU_CSR | LOONGARCH_CPU_VINT;
>> @@ -221,6 +221,11 @@ static void cpu_probe_common(struct cpuinfo_loongarch *c)
>>          if (config & CPUCFG2_LVZP) {
>>                  c->options |= LOONGARCH_CPU_LVZ;
>>                  elf_hwcap |= HWCAP_LOONGARCH_LVZ;
>> +
>> +               /* Separate VMID and VPID with LVZ version == 2 */
>> +               version = (config & CPUCFG2_LVZVER) >> 11;
>> +               if (version == 2)
> I think ">1" judgement is better than "==2".
I am ok with "> 1" and it is better from software side, only that it 
requires that HW keeps compatible with later LVZ function. Will discuss 
this with HW guys.

Regards
Bibo Mao
> 
> 
> Huacai
> 
>> +                       c->options |= LOONGARCH_CPU_GUESTID;
>>          }
>>   #ifdef CONFIG_CPU_HAS_LBT
>>          if (config & CPUCFG2_X86BT) {
>> diff --git a/arch/loongarch/kvm/main.c b/arch/loongarch/kvm/main.c
>> index 86b1af823e2b..43f5b40786f2 100644
>> --- a/arch/loongarch/kvm/main.c
>> +++ b/arch/loongarch/kvm/main.c
>> @@ -365,7 +365,7 @@ int kvm_arch_enable_virtualization_cpu(void)
>>          write_csr_gcfg(0);
>>          write_csr_gstat(0);
>>          write_csr_gintc(0);
>> -       clear_csr_gtlbc(CSR_GTLBC_USETGID | CSR_GTLBC_TOTI);
>> +       clear_csr_gtlbc(CSR_GTLBC_USETGID | CSR_GTLBC_TOTI | CSR_GTLBC_USEVMID);
>>
>>          /*
>>           * Enable virtualization features granting guest direct control of
>> @@ -388,6 +388,8 @@ int kvm_arch_enable_virtualization_cpu(void)
>>
>>          /* Enable using TGID  */
>>          set_csr_gtlbc(CSR_GTLBC_USETGID);
>> +       if (cpu_has_guestid)
>> +               set_csr_gtlbc(CSR_GTLBC_USEVMID);
>>          kvm_debug("GCFG:%lx GSTAT:%lx GINTC:%lx GTLBC:%lx",
>>                    read_csr_gcfg(), read_csr_gstat(), read_csr_gintc(), read_csr_gtlbc());
>>
>> --
>> 2.39.3
>>
>>