Re: [PATCH v3 3/3] target/riscv: add support for svpbmt extension

[Anup Patel]

On Fri, Jan 14, 2022 at 7:11 AM Weiwei Li <liweiwei@iscas.ac.cn> wrote:
>
> It uses two PTE bits, but otherwise has no effect on QEMU, since QEMU is 
> sequentially consistent and doesn't model PMAs currently
>
> Signed-off-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Signed-off-by: Junqiang Wang <wangjunqiang@iscas.ac.cn>
> Tested-by: Heiko Stuebner <heiko@sntech.de>
> ---
>  target/riscv/cpu.c        | 1 +
>  target/riscv/cpu.h        | 1 +
>  target/riscv/cpu_bits.h   | 3 +++
>  target/riscv/cpu_helper.c | 9 ++++++++-
>  4 files changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> index 45ac98e06b..4f82bd00a3 100644
> --- a/target/riscv/cpu.c
> +++ b/target/riscv/cpu.c
> @@ -670,6 +670,7 @@ static Property riscv_cpu_properties[] = {
>
>      DEFINE_PROP_BOOL("svinval", RISCVCPU, cfg.ext_svinval, false),
>      DEFINE_PROP_BOOL("svnapot", RISCVCPU, cfg.ext_svnapot, false),
> +    DEFINE_PROP_BOOL("svpbmt", RISCVCPU, cfg.ext_svpbmt, false),
>
>      DEFINE_PROP_BOOL("zba", RISCVCPU, cfg.ext_zba, true),
>      DEFINE_PROP_BOOL("zbb", RISCVCPU, cfg.ext_zbb, true),
> diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> index c3d1845ca1..53f314c752 100644
> --- a/target/riscv/cpu.h
> +++ b/target/riscv/cpu.h
> @@ -329,6 +329,7 @@ struct RISCVCPU {
>          bool ext_icsr;
>          bool ext_svinval;
>          bool ext_svnapot;
> +        bool ext_svpbmt;
>          bool ext_zfh;
>          bool ext_zfhmin;
>
> diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
> index bc23e3b523..ee294c1d0b 100644
> --- a/target/riscv/cpu_bits.h
> +++ b/target/riscv/cpu_bits.h
> @@ -486,7 +486,10 @@ typedef enum {
>  #define PTE_A               0x040 /* Accessed */
>  #define PTE_D               0x080 /* Dirty */
>  #define PTE_SOFT            0x300 /* Reserved for Software */
> +#define PTE_RSVD            0x1FC0000000000000 /* Reserved for future use */
> +#define PTE_PBMT            0x6000000000000000 /* Page-based memory types */
>  #define PTE_N               0x8000000000000000 /* NAPOT translation */
> +#define PTE_ATTR            0xFFC0000000000000 /* All attributes bits */
>
>  /* Page table PPN shift amount */
>  #define PTE_PPN_SHIFT       10
> diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
> index 58ab85bca3..f90766e026 100644
> --- a/target/riscv/cpu_helper.c
> +++ b/target/riscv/cpu_helper.c
> @@ -619,16 +619,23 @@ restart:
>              return TRANSLATE_FAIL;
>          }
>
> -        hwaddr ppn = (pte & ~(target_ulong)PTE_N) >> PTE_PPN_SHIFT;
> +        hwaddr ppn = (pte & ~(target_ulong)PTE_ATTR) >> PTE_PPN_SHIFT;
>
>          RISCVCPU *cpu = env_archcpu(env);
>          if (!cpu->cfg.ext_svnapot && (pte & PTE_N)) {
>              return TRANSLATE_FAIL;
> +        } else if (!cpu->cfg.ext_svpbmt && (pte & PTE_PBMT)) {
> +            return TRANSLATE_FAIL;
> +        } else if (pte & PTE_RSVD) {
> +            return TRANSLATE_FAIL;
>          } else if (!(pte & PTE_V)) {
>              /* Invalid PTE */
>              return TRANSLATE_FAIL;
>          } else if (!(pte & (PTE_R | PTE_W | PTE_X))) {
>              /* Inner PTE, continue walking */
> +            if (pte & (PTE_D | PTE_A | PTE_U | PTE_N | PTE_PBMT)) {
> +                return TRANSLATE_FAIL;
> +            }

I think you should add a patch before PATCH1 to add following:

if (pte & (PTE_D | PTE_A | PTE_U)) {
    return TRANSLATE_FAIL;
}

The current PATCH1 should add PTE_N to the comparison and
this patch can add PTE_PBMT to the comparison.

>              base = ppn << PGSHIFT;
>          } else if ((pte & (PTE_R | PTE_W | PTE_X)) == PTE_W) {
>              /* Reserved leaf PTE flags: PTE_W */
> --
> 2.17.1
>

Apart from the minor comment above, it looks good to me.

Reviewed-by: Anup Patel <anup@brainfault.org>

Regards,
Anup