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UPSTREAM: arm64/signal: Flush FPSIMD register state when disabling streaming mode

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When handling a signal delivered to a context with streaming mode enabled
we will disable streaming mode for the signal handler, when doing so we
should also flush the saved FPSIMD register state like exiting streaming
mode in the hardware would do so that if that state is reloaded we get the
same behaviour. Without this we will reload whatever the last FPSIMD state
that was saved for the task was.

Bug: 254441685
Fixes: 40a8e87bb3 ("arm64/sme: Disable ZA and streaming mode when handling signals")
Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220817182324.638214-3-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>
(cherry picked from commit ea64baacbc)
Signed-off-by: Lee Jones <joneslee@google.com>
Change-Id: Ieb48103e6829088e41d05718ad9c5ff6319ae516
This commit is contained in:
Mark Brown
2022-08-17 19:23:22 +01:00
committed by Treehugger Robot
parent e02ea83370
commit 17d78f2270
1 changed files with 10 additions and 0 deletions
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10
arch/arm64/kernel/signal.c
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@@ -923,6 +923,16 @@ static void setup_return(struct pt_regs *regs, struct k_sigaction *ka,
/* Signal handlers are invoked with ZA and streaming mode disabled */
if (system_supports_sme()) {
/*
* If we were in streaming mode the saved register
* state was SVE but we will exit SM and use the
* FPSIMD register state - flush the saved FPSIMD
* register state in case it gets loaded.
*/
if (current->thread.svcr & SVCR_SM_MASK)
memset(&current->thread.uw.fpsimd_state, 0,
sizeof(current->thread.uw.fpsimd_state));
current->thread.svcr &= ~(SVCR_ZA_MASK |
SVCR_SM_MASK);
sme_smstop();