From: Nathan Lynch <nathanl@linux.ibm.com>
To: Alexey Kardashevskiy <aik@ozlabs.ru>, linuxppc-dev@lists.ozlabs.org
Cc: tyreld@linux.ibm.com, brking@linux.ibm.com, ajd@linux.ibm.com,
aneesh.kumar@linux.ibm.com
Subject: Re: [PATCH 5/6] powerpc/rtas: rename RTAS_RMOBUF_MAX to RTAS_USER_REGION_SIZE
Date: Fri, 15 Jan 2021 09:56:32 -0600 [thread overview]
Message-ID: <87a6taxkgf.fsf@linux.ibm.com> (raw)
In-Reply-To: <d91c5b15-7c3d-a332-45ac-1b865341e962@ozlabs.ru>
Alexey Kardashevskiy <aik@ozlabs.ru> writes:
> On 15/01/2021 09:00, Nathan Lynch wrote:
>> diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h
>> index 332e1000ca0f..1aa7ab1cbc84 100644
>> --- a/arch/powerpc/include/asm/rtas.h
>> +++ b/arch/powerpc/include/asm/rtas.h
>> @@ -19,8 +19,11 @@
>> #define RTAS_UNKNOWN_SERVICE (-1)
>> #define RTAS_INSTANTIATE_MAX (1ULL<<30) /* Don't instantiate rtas at/above this value */
>>
>> -/* Buffer size for ppc_rtas system call. */
>> -#define RTAS_RMOBUF_MAX (64 * 1024)
>> +/* Work areas shared with RTAS must be 4K, naturally aligned. */
>
> Why exactly 4K and not (for example) PAGE_SIZE?
4K is a platform requirement and isn't related to Linux's configured
page size. See the PAPR specification for RTAS functions such as
ibm,configure-connector, ibm,update-nodes, ibm,update-properties.
There are other calls with work area parameters where alignment isn't
specified (e.g. ibm,get-system-parameter) but 4KB alignment is a safe
choice for those.
>> +#define RTAS_WORK_AREA_SIZE 4096
>> +
>> +/* Work areas allocated for user space access. */
>> +#define RTAS_USER_REGION_SIZE (RTAS_WORK_AREA_SIZE * 16)
>
> This is still 64K but no clarity why. There is 16 of something, what
> is it?
There are 16 4KB work areas in the region. I can name it
RTAS_NR_USER_WORK_AREAS or similar.
next prev parent reply other threads:[~2021-01-15 15:58 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-14 21:59 [PATCH 0/6] powerpc/rtas: miscellaneous cleanups, user region allocation Nathan Lynch
2021-01-14 21:59 ` [PATCH 1/6] powerpc/rtas: improve ppc_rtas_rmo_buf_show documentation Nathan Lynch
2021-01-15 4:38 ` Alexey Kardashevskiy
2021-01-15 5:50 ` Andrew Donnellan
2021-01-14 22:00 ` [PATCH 2/6] powerpc/rtas-proc: remove unused RMO_READ_BUF_MAX Nathan Lynch
2021-01-15 4:38 ` Alexey Kardashevskiy
2021-01-15 5:52 ` Andrew Donnellan
2021-01-14 22:00 ` [PATCH 3/6] powerpc/rtas: remove ibm_suspend_me_token Nathan Lynch
2021-01-15 4:38 ` Alexey Kardashevskiy
2021-01-15 5:52 ` Andrew Donnellan
2021-01-14 22:00 ` [PATCH 4/6] powerpc/rtas: move syscall filter setup into separate function Nathan Lynch
2021-01-15 4:39 ` Alexey Kardashevskiy
2021-01-15 16:04 ` Nathan Lynch
2021-01-15 5:49 ` Andrew Donnellan
2021-01-14 22:00 ` [PATCH 5/6] powerpc/rtas: rename RTAS_RMOBUF_MAX to RTAS_USER_REGION_SIZE Nathan Lynch
2021-01-15 4:38 ` Alexey Kardashevskiy
2021-01-15 15:56 ` Nathan Lynch [this message]
2021-01-18 4:15 ` Alexey Kardashevskiy
2021-01-20 1:17 ` Nathan Lynch
2021-01-20 5:05 ` Alexey Kardashevskiy
2021-01-21 15:17 ` Nathan Lynch
2021-01-15 6:10 ` Andrew Donnellan
2021-01-15 12:04 ` kernel test robot
2021-01-15 12:04 ` kernel test robot
2021-01-14 22:00 ` [PATCH 6/6] powerpc/rtas: constrain user region allocation to RMA Nathan Lynch
2021-01-15 4:38 ` Alexey Kardashevskiy
2021-01-15 15:38 ` Nathan Lynch
2021-01-18 4:12 ` Alexey Kardashevskiy
2021-01-20 0:39 ` Nathan Lynch
2021-01-20 4:49 ` Alexey Kardashevskiy
2021-01-20 12:06 ` Michael Ellerman
2021-01-21 15:27 ` Nathan Lynch
2021-01-23 1:54 ` Alexey Kardashevskiy
2021-01-19 9:00 ` Michael Ellerman
2021-01-19 21:00 ` Nathan Lynch
2021-01-20 12:13 ` Michael Ellerman
2021-01-21 0:26 ` Nathan Lynch
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