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

[Huacai Chen]

Hi, Bibo,

On Mon, Jul 27, 2026 at 3:31 PM Bibo Mao <maobibo@xxxxxxxxxxx> 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 <maobibo@xxxxxxxxxxx>
> ---
>  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".


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
>
>