diff mbox series

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

Message ID 20250114021936.17234-3-cuiyunhui@bytedance.com (mailing list archive)
State New
Headers show
Series Enable Zicbom in usermode | expand

Commit Message

Yunhui Cui Jan. 14, 2025, 2:19 a.m. UTC
Expose Zicbom through hwprobe and also provide a key to extract its
respective block size.

Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
---
 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(-)

Comments

Samuel Holland Jan. 14, 2025, 5:28 a.m. UTC | #1
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@bytedance.com>
> ---
>  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.

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;
Yunhui Cui Jan. 14, 2025, 12:17 p.m. UTC | #2
Hi Samuel,

On Tue, Jan 14, 2025 at 1:28 PM Samuel Holland
<samuel.holland@sifive.com> 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@bytedance.com>
> > ---
> >  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?

>
> 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
Andrew Jones Jan. 14, 2025, 12:42 p.m. UTC | #3
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@sifive.com> 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@bytedance.com>
> > > ---
> > >  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
diff mbox series

Patch

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.
 
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;