2023-06-09 23:05:23

by Mark Brown

Subject: [PATCH v2] arm64/fpsimd: Exit streaming mode when flushing tasks

Ensure there is no path where we might attempt to save SME state after we
flush a task by updating the SVCR register state as well as updating our
in memory state. I haven't seen a specific case where this is happening or
seen a path where it might happen but for the cost of a single low overhead
instruction it seems sensible to close the potential gap.

Signed-off-by: Mark Brown <[email protected]>
---
Changes in v2:
- Do a full SMSTOP to cover ZA as well.
- Link to v1: https://lore.kernel.org/r/[email protected]
---
arch/arm64/kernel/fpsimd.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 2fbafa5cc7ac..7a1aeb95d7c3 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -1649,6 +1649,7 @@ void fpsimd_flush_thread(void)

fpsimd_flush_thread_vl(ARM64_VEC_SME);
current->thread.svcr = 0;
+ sme_smstop();
}

current->thread.fp_type = FP_STATE_FPSIMD;

---
base-commit: 44c026a73be8038f03dbdeef028b642880cf1511
change-id: 20230607-arm64-flush-svcr-47cc76a8cbbc

Best regards,
--
Mark Brown <[email protected]>

2023-06-16 18:05:22

by Catalin Marinas

Subject: Re: [PATCH v2] arm64/fpsimd: Exit streaming mode when flushing tasks

On Fri, 09 Jun 2023 23:43:41 +0100, Mark Brown wrote:
> Ensure there is no path where we might attempt to save SME state after we
> flush a task by updating the SVCR register state as well as updating our
> in memory state. I haven't seen a specific case where this is happening or
> seen a path where it might happen but for the cost of a single low overhead
> instruction it seems sensible to close the potential gap.
>
>
> [...]

Applied to arm64 (for-next/misc), thanks!

[1/1] arm64/fpsimd: Exit streaming mode when flushing tasks
https://git.kernel.org/arm64/c/af3215fd0230

--
Catalin