Re: [PATCH v6 1/5] target/riscv: Ignore reserved bits in PTE for RV64

[LIU Zhiwei]

On 2022/1/25 16:40, Guo Ren wrote:
> On Tue, Jan 25, 2022 at 4:34 PM LIU Zhiwei <zhiwei_liu@c-sky.com> wrote:
> > On 2022/1/25 14:45, Weiwei Li wrote:
> > > From: Guo Ren <ren_guo@c-sky.com>
> > >
> > > Highest bits of PTE has been used for svpbmt, ref: [1], [2], so we
> > > need to ignore them. They cannot be a part of ppn.
> > >
> > > 1: The RISC-V Instruction Set Manual, Volume II: Privileged Architecture
> > >      4.4 Sv39: Page-Based 39-bit Virtual-Memory System
> > >      4.5 Sv48: Page-Based 48-bit Virtual-Memory System
> > >
> > > 2: https://github.com/riscv/virtual-memory/blob/main/specs/663-Svpbmt-diff.pdf
> > >
> > > Signed-off-by: Guo Ren <ren_guo@c-sky.com>
> > > Cc: Liu Zhiwei <zhiwei_liu@c-sky.com>
> > > Cc: Bin Meng <bmeng.cn@gmail.com>
> > > Cc: Alistair Francis <alistair.francis@wdc.com>
> > > ---
> > >    target/riscv/cpu.h        | 13 +++++++++++++
> > >    target/riscv/cpu_bits.h   |  7 +++++++
> > >    target/riscv/cpu_helper.c | 14 +++++++++++++-
> > >    3 files changed, 33 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
> > > index 55635d68d5..45de8faaca 100644
> > > --- a/target/riscv/cpu.h
> > > +++ b/target/riscv/cpu.h
> > > @@ -341,6 +341,8 @@ struct RISCVCPU {
> > >            bool ext_counters;
> > >            bool ext_ifencei;
> > >            bool ext_icsr;
> > > +        bool ext_svnapot;
> > > +        bool ext_svpbmt;
> > >            bool ext_zfh;
> > >            bool ext_zfhmin;
> > >            bool ext_zve32f;
> > > @@ -495,6 +497,17 @@ static inline int riscv_cpu_xlen(CPURISCVState *env)
> > >        return 16 << env->xl;
> > >    }
> > >
> > > +#ifndef CONFIG_USER_ONLY
> > > +#ifdef TARGET_RISCV32
> > > +#define riscv_cpu_sxl(env)  ((void)(env), MXL_RV32)
> > > +#else
> > > +static inline RISCVMXL riscv_cpu_sxl(CPURISCVState *env)
> > > +{
> > > +    return get_field(env->mstatus, MSTATUS64_SXL);
> > > +}
> > > +#endif
> > > +#endif
> > > +
> > Perhaps an interface also works for user mode is better.
> >
> > +#ifdef TARGET_RISCV32
> > +#define riscv_cpu_sxl(env)  ((void)(env), MXL_RV32)
> > +#else
> > +static inline RISCVMXL riscv_cpu_sxl(CPURISCVState *env)
> > +{
> > +#ifdef CONFIG_USER_ONLY
> > +    return env->misa_mxl;
> > +#else
> > +    return get_field(env->mstatus, MSTATUS64_SXL);
> > +#endif
> > +}
> > +#endif
> > +
> >
> > >    /*
> > >     * Encode LMUL to lmul as follows:
> > >     *     LMUL    vlmul    lmul
> > > diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
> > > index 7c87433645..37b622fbfa 100644
> > > --- a/target/riscv/cpu_bits.h
> > > +++ b/target/riscv/cpu_bits.h
> > > @@ -493,6 +493,13 @@ typedef enum {
> > >    /* Page table PPN shift amount */
> > >    #define PTE_PPN_SHIFT       10
> > >
> > > +/* Page table PPN mask */
> > > +#if defined(TARGET_RISCV32)
> > > +#define PTE_PPN_MASK        0xFFFFFC00UL
> > > +#elif defined(TARGET_RISCV64)
> > > +#define PTE_PPN_MASK        0x3FFFFFFFFFFC00ULL
> > > +#endif
> > > +
> > No need to define PTE_PPN_MASK for TARGET_RISCV32.
> ppn = (pte & PTE_PPN_MASK) >> PTE_PPN_SHIFT;
>
> pte is target_ulong, so types are different.
>
> TARGET_RISCV32: is 32bit.
> TARGET_RISCV64: is 64bit.
I should make it more clear.  You will not use PTE_PPN_MASK on 
TARGET_RISCV32.
> > >    /* Leaf page shift amount */
> > >    #define PGSHIFT             12
> > >
> > > diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
> > > index 327a2c4f1d..2a921bedfd 100644
> > > --- a/target/riscv/cpu_helper.c
> > > +++ b/target/riscv/cpu_helper.c
> > > @@ -622,7 +622,19 @@ restart:
> > >                return TRANSLATE_FAIL;
> > >            }
> > >
> > > -        hwaddr ppn = pte >> PTE_PPN_SHIFT;
> > > +        hwaddr ppn;
> > > +        RISCVCPU *cpu = env_archcpu(env);
> > > +
> > > +        if (riscv_cpu_sxl(env) == MXL_RV32) {
> > > +            ppn = pte >> PTE_PPN_SHIFT;

TARGET_RISCV32 will always come here. So no need to define PTE_PPN_MASK 
for TARGET_RISCV32.

Thanks,
Zhiwei

> > > +        } else if (cpu->cfg.ext_svpbmt || cpu->cfg.ext_svnapot) {
> > > +            ppn = (pte & PTE_PPN_MASK) >> PTE_PPN_SHIFT;
> > > +        } else {
> > > +            ppn = pte >> PTE_PPN_SHIFT;
> > > +            if ((pte & ~PTE_PPN_MASK) >> PTE_PPN_SHIFT) {
> > > +                return TRANSLATE_FAIL;
> > > +            }
> > > +        }
> > >
> > >            if (!(pte & PTE_V)) {
> > >                /* Invalid PTE */
> > Otherwise,
> >
> > Reviewed-by: LIU Zhiwei <zhiwei_liu@c-sky.com>
> >
> > Thanks,
> > Zhiwei