From: Eric Biggers <ebiggers@kernel.org>
To: Ard Biesheuvel <ardb@google.com>
Cc: linux-arm-kernel@lists.infradead.org,
Ard Biesheuvel <ardb@kernel.org>, Marc Zyngier <maz@kernel.org>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Kees Cook <keescook@chromium.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Mark Brown <broonie@kernel.org>
Subject: Re: [PATCH v2 2/4] arm64: fpsimd: Preserve/restore kernel mode NEON at context switch
Date: Thu, 23 Nov 2023 16:14:30 -0800 [thread overview]
Message-ID: <20231124001430.GB13943@sol.localdomain> (raw)
In-Reply-To: <20231123174433.737171-8-ardb@google.com>
On Thu, Nov 23, 2023 at 06:44:36PM +0100, Ard Biesheuvel wrote:
> - /*
> - * Fix up TIF_FOREIGN_FPSTATE to correctly describe next's
> - * state. For kernel threads, FPSIMD registers are never loaded
> - * and wrong_task and wrong_cpu will always be true.
> - */
> - wrong_task = __this_cpu_read(fpsimd_last_state.st) !=
> - &next->thread.uw.fpsimd_state;
> - wrong_cpu = next->thread.fpsimd_cpu != smp_processor_id();
> + if (test_tsk_thread_flag(next, TIF_USING_KMODE_FPSIMD)) {
> + fpsimd_load_kernel_state(next);
> + set_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE);
> + } else {
> + /*
> + * Fix up TIF_FOREIGN_FPSTATE to correctly describe next's
> + * state. For kernel threads, FPSIMD registers are never
> + * loaded and wrong_task and wrong_cpu will always be true.
> + */
> + wrong_task = __this_cpu_read(fpsimd_last_state.st) !=
> + &next->thread.uw.fpsimd_state;
> + wrong_cpu = next->thread.fpsimd_cpu != smp_processor_id();
The "For kernel threads, FPSIMD registers are never loaded" part is outdated
now, right?
- Eric
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next prev parent reply other threads:[~2023-11-24 0:15 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-23 17:44 [PATCH v2 0/4] arm64: Run kernel mode NEON with preemption enabled Ard Biesheuvel
2023-11-23 17:44 ` [PATCH v2 1/4] arm64: fpsimd: Drop unneeded 'busy' flag Ard Biesheuvel
2023-11-23 17:44 ` [PATCH v2 2/4] arm64: fpsimd: Preserve/restore kernel mode NEON at context switch Ard Biesheuvel
2023-11-24 0:14 ` Eric Biggers [this message]
2023-11-24 8:29 ` Ard Biesheuvel
2023-11-24 12:28 ` Mark Brown
2023-11-23 17:44 ` [PATCH v2 3/4] arm64: fpsimd: Implement lazy restore for kernel mode FPSIMD Ard Biesheuvel
2023-11-24 12:31 ` Mark Brown
2023-11-23 17:44 ` [PATCH v2 4/4] arm64: crypto: Remove conditional yield logic Ard Biesheuvel
2023-11-24 0:11 ` [PATCH v2 0/4] arm64: Run kernel mode NEON with preemption enabled Eric Biggers
2023-11-24 15:53 ` Ard Biesheuvel
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