Re: [PATCH] arm64/signal: Don't assume that TIF_SVE means we saved SVE state
From: Dave Martin <Dave.Martin@arm.com>
Date: 2024-01-19 16:31:19
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On Fri, Jan 19, 2024 at 12:29:13PM +0000, Mark Brown wrote:
When we are in a syscall we will only save the FPSIMD subset even though the task still has access to the full register set, and on context switch
(Pedantic nit: "A even if B" (= "A applies even in that subset of cases where B"), instead of "A even though B" (= "A applies notwithstanding that it is always the case that B") (?) If the SVE trapping were ripped out altogether, it would be a different and rather simpler story...)
quoted hunk ↗ jump to hunk
we will only remove TIF_SVE when loading the register state. This means that the signal handling code should not assume that TIF_SVE means that the register state is stored in SVE format, it should instead check the format that was recorded during save. Fixes: 8c845e273104 ("arm64/sve: Leave SVE enabled on syscall if we don't context switch") Signed-off-by: Mark Brown <broonie@kernel.org> Cc: <redacted> --- arch/arm64/kernel/fpsimd.c | 2 +- arch/arm64/kernel/signal.c | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-)diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 1559c706d32d..80133c190136 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c@@ -1626,7 +1626,7 @@ void fpsimd_preserve_current_state(void) void fpsimd_signal_preserve_current_state(void) { fpsimd_preserve_current_state(); - if (test_thread_flag(TIF_SVE)) + if (current->thread.fp_type == FP_STATE_SVE) sve_to_fpsimd(current); }diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c index 0e8beb3349ea..425b1bc17a3f 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c@@ -242,7 +242,7 @@ static int preserve_sve_context(struct sve_context __user *ctx) vl = task_get_sme_vl(current); vq = sve_vq_from_vl(vl); flags |= SVE_SIG_FLAG_SM; - } else if (test_thread_flag(TIF_SVE)) { + } else if (current->thread.fp_type == FP_STATE_SVE) { vq = sve_vq_from_vl(vl); }@@ -878,7 +878,7 @@ static int setup_sigframe_layout(struct rt_sigframe_user_layout *user, if (system_supports_sve() || system_supports_sme()) { unsigned int vq = 0; - if (add_all || test_thread_flag(TIF_SVE) || + if (add_all || current->thread.fp_type == FP_STATE_SVE || thread_sm_enabled(¤t->thread)) { int vl = max(sve_max_vl(), sme_max_vl());--- base-commit: 0dd3ee31125508cd67f7e7172247f05b7fd1753a change-id: 20240118-arm64-sve-signal-regs-5711e0d10425 Best regards, -- Mark Brown [off-list ref]
[...] If the historical meanings of TIF_SVE have been split up (which seems a good idea), does that resolve all of the "bare" test_thread_flag(TIF_SVE) that were still there? If there are any others remaining, they may need looking at if there is any question over what condition they are trying to test for... Cheers ---Dave _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel