Re: [PATCH v2 5/5] LoongArch: KVM: Enable separate vmid feature

On Thu, Aug 6, 2026 at 8:55 PM Bibo Mao <[email protected]> wrote:
>
>
>
> On 2026/8/6 下午8:39, Huacai Chen wrote:
> > Hi, Bibo,
> >
> > On Thu, Aug 6, 2026 at 10:15 AM 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 | 5 +++++
> >>   arch/loongarch/kernel/cpu-probe.c      | 6 ++++++
> >>   arch/loongarch/kvm/main.c              | 4 +++-
> >>   3 files changed, 14 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
> >> index 2a6bc99177d8..a20fb68d8ac4 100644
> >> --- a/arch/loongarch/include/asm/loongarch.h
> >> +++ b/arch/loongarch/include/asm/loongarch.h
> >> @@ -138,6 +138,9 @@
> >>   #define  CPUCFG6_PMBITS_SHIFT          8
> >>   #define  CPUCFG6_UPM                   BIT(14)
> >>
> >> +#define LOONGARCH_CPUCFG8              0x8
> >> +#define  CPUCFG8_VMID                  BIT(8)
> >> +
> >>   #define LOONGARCH_CPUCFG16             0x10
> >>   #define  CPUCFG16_L1_IUPRE             BIT(0)
> >>   #define  CPUCFG16_L1_IUUNIFY           BIT(1)
> >> @@ -350,6 +353,8 @@
> >>   #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)
> >
> > Other fields in GTLBC is TGID, so it is better to name it
> > CSR_GTLBC_USETGID, just use vpid/vmid for software purely.
>   - clear_csr_gtlbc(CSR_GTLBC_USETGID | CSR_GTLBC_TOTI);
>   + clear_csr_gtlbc(CSR_GTLBC_USETGID | CSR_GTLBC_TOTI | CSR_GTLBC_USEVMID);
>
> There is CSR_GTLBC_USETGID enabled already which it bit 12 :)
Emmm, what is the difference between bit 12 and bit 14?

Huacai

>
> >
> >
> >
> > Huacai
> >
> >>   #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..fc68f695d49c 100644
> >> --- a/arch/loongarch/kernel/cpu-probe.c
> >> +++ b/arch/loongarch/kernel/cpu-probe.c
> >> @@ -241,6 +241,12 @@ static void cpu_probe_common(struct cpuinfo_loongarch *c)
> >>          if (config & CPUCFG6_PMP)
> >>                  c->options |= LOONGARCH_CPU_PMP;
> >>
> >> +       if (c->options & LOONGARCH_CPU_LVZ) {
> >> +               config = read_cpucfg(LOONGARCH_CPUCFG8);
> >> +               if (config & CPUCFG8_VMID)
> >> +                       c->options |= LOONGARCH_CPU_GUESTID;
> >> +       }
> >> +
> >>          config = csr_read32(LOONGARCH_CSR_ASID);
> >>          config = (config & CSR_ASID_BIT) >> CSR_ASID_BIT_SHIFT;
> >>          asid_mask = GENMASK(config - 1, 0);
> >> diff --git a/arch/loongarch/kvm/main.c b/arch/loongarch/kvm/main.c
> >> index 72c1d23156e5..712b078db0d5 100644
> >> --- a/arch/loongarch/kvm/main.c
> >> +++ b/arch/loongarch/kvm/main.c
> >> @@ -359,7 +359,7 @@ 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
> >> @@ -382,6 +382,8 @@ 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
> >>
>