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Re: [PATCH v3 11/20] target/arm: default SVE length to 64 bytes for linu
From: |
Richard Henderson |
Subject: |
Re: [PATCH v3 11/20] target/arm: default SVE length to 64 bytes for linux-user |
Date: |
Wed, 11 Dec 2019 18:09:13 -0800 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.1 |
On 12/11/19 9:05 AM, Alex Bennée wrote:
> The Linux kernel chooses the default of 64 bytes for SVE registers on
> the basis that it is the largest size on known hardware that won't
> grow the signal frame. We still honour the sve-max-vq property and
> userspace can expand the number of lanes by calling PR_SVE_SET_VL.
>
> This should not make any difference to SVE enabled software as the SVE
> is of course vector length agnostic.
>
> Signed-off-by: Alex Bennée <address@hidden>
>
> ---
> v2
> - tweak zcr_el[1] instead
> ---
> target/arm/cpu.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/target/arm/cpu.c b/target/arm/cpu.c
> index 7a4ac9339bf..d42b88c9b73 100644
> --- a/target/arm/cpu.c
> +++ b/target/arm/cpu.c
> @@ -199,9 +199,9 @@ static void arm_cpu_reset(CPUState *s)
> /* and to the SVE instructions */
> env->cp15.cpacr_el1 = deposit64(env->cp15.cpacr_el1, 16, 2, 3);
> env->cp15.cptr_el[3] |= CPTR_EZ;
> - /* with maximum vector length */
> + /* with reasonable vector length */
I think this comment should mention the kernel as well. Otherwise,
Reviewed-by: Richard Henderson <address@hidden>
r~
- [PATCH v3 04/20] gdbstub: move mem_buf to GDBState and use GByteArray, (continued)
- [PATCH v3 04/20] gdbstub: move mem_buf to GDBState and use GByteArray, Alex Bennée, 2019/12/11
- [PATCH v3 06/20] target/arm: use gdb_get_reg helpers, Alex Bennée, 2019/12/11
- [PATCH v3 03/20] gdbstub: move str_buf to GDBState and use GString, Alex Bennée, 2019/12/11
- [PATCH v3 07/20] target/m68k: use gdb_get_reg helpers, Alex Bennée, 2019/12/11
- [PATCH v3 10/20] target/arm: explicitly encode regnum in our XML, Alex Bennée, 2019/12/11
- [PATCH v3 11/20] target/arm: default SVE length to 64 bytes for linux-user, Alex Bennée, 2019/12/11
- Re: [PATCH v3 11/20] target/arm: default SVE length to 64 bytes for linux-user,
Richard Henderson <=
- [PATCH v3 09/20] target/arm: prepare for multiple dynamic XMLs, Alex Bennée, 2019/12/11
- [PATCH v3 19/20] tests/tcg/aarch64: add SVE iotcl test, Alex Bennée, 2019/12/11
- [PATCH v3 13/20] tests/tcg: add a configure compiler check for ARMv8.1 and SVE, Alex Bennée, 2019/12/11
- [PATCH v3 02/20] gdbstub: stop passing GDBState * around and use global, Alex Bennée, 2019/12/11
- [PATCH v3 08/20] gdbstub: extend GByteArray to read register helpers, Alex Bennée, 2019/12/11
- [PATCH v3 15/20] tests/tcg/aarch64: userspace system register test, Alex Bennée, 2019/12/11