Re: [External] Re: [PATCH v4 2/3] RISC-V: hwprobe: Expose Zicbom extension and its block size

[Andrew Jones]

On Tue, Jan 14, 2025 at 08:17:02PM +0800, yunhui cui wrote:
> Hi Samuel，
> 
> On Tue, Jan 14, 2025 at 1:28 PM Samuel Holland
> <samuel.holland@xxxxxxxxxx> wrote:
> >
> > Hi Yunhui,
> >
> > On 2025-01-13 8:19 PM, Yunhui Cui wrote:
> > > Expose Zicbom through hwprobe and also provide a key to extract its
> > > respective block size.
> > >
> > > Signed-off-by: Yunhui Cui <cuiyunhui@xxxxxxxxxxxxx>
> > > ---
> > >  Documentation/arch/riscv/hwprobe.rst  | 6 ++++++
> > >  arch/riscv/include/asm/hwprobe.h      | 2 +-
> > >  arch/riscv/include/uapi/asm/hwprobe.h | 2 ++
> > >  arch/riscv/kernel/sys_hwprobe.c       | 6 ++++++
> > >  4 files changed, 15 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
> > > index 955fbcd19ce9..0ea7754b2049 100644
> > > --- a/Documentation/arch/riscv/hwprobe.rst
> > > +++ b/Documentation/arch/riscv/hwprobe.rst
> > > @@ -242,6 +242,9 @@ The following keys are defined:
> > >    * :c:macro:`RISCV_HWPROBE_EXT_SUPM`: The Supm extension is supported as
> > >         defined in version 1.0 of the RISC-V Pointer Masking extensions.
> > >
> > > +  * :c:macro:`RISCV_HWPROBE_EXT_ZICBOM`: The Zicbom extension is supported, as
> > > +       ratified in commit 3dd606f ("Create cmobase-v1.0.pdf") of riscv-CMOs.
> > > +
> > >  * :c:macro:`RISCV_HWPROBE_KEY_CPUPERF_0`: Deprecated.  Returns similar values to
> > >       :c:macro:`RISCV_HWPROBE_KEY_MISALIGNED_SCALAR_PERF`, but the key was
> > >       mistakenly classified as a bitmask rather than a value.
> > > @@ -281,6 +284,9 @@ The following keys are defined:
> > >  * :c:macro:`RISCV_HWPROBE_KEY_MISALIGNED_VECTOR_PERF`: An enum value describing the
> > >       performance of misaligned vector accesses on the selected set of processors.
> > >
> > > +* :c:macro:`RISCV_HWPROBE_KEY_ZICBOM_BLOCK_SIZE`: An unsigned int which
> > > +  represents the size of the Zicbom block in bytes.
> > > +
> > >    * :c:macro:`RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN`: The performance of misaligned
> > >      vector accesses is unknown.
> >
> > The new key needs to go further down, below this list of possible values for the
> > previous key.
> I guess you mean to put it after
> RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED, right?

Yes, notice how all the RISCV_HWPROBE_MISALIGNED_VECTOR_* defines are
indented under RISCV_HWPROBE_KEY_MISALIGNED_VECTOR_PERF indicating
they're part of the RISCV_HWPROBE_KEY_MISALIGNED_VECTOR_PERF group.

Thanks,
drew

> 
> >
> > Regards,
> > Samuel
> >
> > >
> > > diff --git a/arch/riscv/include/asm/hwprobe.h b/arch/riscv/include/asm/hwprobe.h
> > > index 1ce1df6d0ff3..89379f9a2e6e 100644
> > > --- a/arch/riscv/include/asm/hwprobe.h
> > > +++ b/arch/riscv/include/asm/hwprobe.h
> > > @@ -8,7 +8,7 @@
> > >
> > >  #include <uapi/asm/hwprobe.h>
> > >
> > > -#define RISCV_HWPROBE_MAX_KEY 10
> > > +#define RISCV_HWPROBE_MAX_KEY 11
> > >
> > >  static inline bool riscv_hwprobe_key_is_valid(__s64 key)
> > >  {
> > > diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
> > > index 3af142b99f77..b15c0bd83ef2 100644
> > > --- a/arch/riscv/include/uapi/asm/hwprobe.h
> > > +++ b/arch/riscv/include/uapi/asm/hwprobe.h
> > > @@ -73,6 +73,7 @@ struct riscv_hwprobe {
> > >  #define              RISCV_HWPROBE_EXT_ZCMOP         (1ULL << 47)
> > >  #define              RISCV_HWPROBE_EXT_ZAWRS         (1ULL << 48)
> > >  #define              RISCV_HWPROBE_EXT_SUPM          (1ULL << 49)
> > > +#define              RISCV_HWPROBE_EXT_ZICBOM        (1ULL << 50)
> > >  #define RISCV_HWPROBE_KEY_CPUPERF_0  5
> > >  #define              RISCV_HWPROBE_MISALIGNED_UNKNOWN        (0 << 0)
> > >  #define              RISCV_HWPROBE_MISALIGNED_EMULATED       (1 << 0)
> > > @@ -94,6 +95,7 @@ struct riscv_hwprobe {
> > >  #define              RISCV_HWPROBE_MISALIGNED_VECTOR_SLOW            2
> > >  #define              RISCV_HWPROBE_MISALIGNED_VECTOR_FAST            3
> > >  #define              RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED     4
> > > +#define RISCV_HWPROBE_KEY_ZICBOM_BLOCK_SIZE  11
> > >  /* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
> > >
> > >  /* Flags */
> > > diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
> > > index cb93adfffc48..04150e62f998 100644
> > > --- a/arch/riscv/kernel/sys_hwprobe.c
> > > +++ b/arch/riscv/kernel/sys_hwprobe.c
> > > @@ -106,6 +106,7 @@ static void hwprobe_isa_ext0(struct riscv_hwprobe *pair,
> > >               EXT_KEY(ZCA);
> > >               EXT_KEY(ZCB);
> > >               EXT_KEY(ZCMOP);
> > > +             EXT_KEY(ZICBOM);
> > >               EXT_KEY(ZICBOZ);
> > >               EXT_KEY(ZICOND);
> > >               EXT_KEY(ZIHINTNTL);
> > > @@ -278,6 +279,11 @@ static void hwprobe_one_pair(struct riscv_hwprobe *pair,
> > >               if (hwprobe_ext0_has(cpus, RISCV_HWPROBE_EXT_ZICBOZ))
> > >                       pair->value = riscv_cboz_block_size;
> > >               break;
> > > +     case RISCV_HWPROBE_KEY_ZICBOM_BLOCK_SIZE:
> > > +             pair->value = 0;
> > > +             if (hwprobe_ext0_has(cpus, RISCV_HWPROBE_EXT_ZICBOM))
> > > +                     pair->value = riscv_cbom_block_size;
> > > +             break;
> > >       case RISCV_HWPROBE_KEY_HIGHEST_VIRT_ADDRESS:
> > >               pair->value = user_max_virt_addr();
> > >               break;
> >
> 
> Thanks,
> Yunhui