From: Ingo Molnar <mingo@kernel.org>
To: Eric Biggers <ebiggers@kernel.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
linux-crypto@vger.kernel.org, linux-pm@vger.kernel.org,
Borislav Petkov <bp@alien8.de>,
Thomas Gleixner <tglx@linutronix.de>,
Ayush Jain <Ayush.Jain3@amd.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
Ard Biesheuvel <ardb@kernel.org>
Subject: Re: [PATCH 3/3] x86/fpu: Don't support kernel-mode FPU when irqs_disabled()
Date: Sun, 18 May 2025 08:34:25 +0200 [thread overview]
Message-ID: <aCl_cSO2XqtSQEZT@gmail.com> (raw)
In-Reply-To: <20250517183919.GC1239@sol>
* Eric Biggers <ebiggers@kernel.org> wrote:
> > Alternatively we could set in_kernel_fpu during CPU bootstrap, and
> > clear it once we know the FPU is usable? This is only a relatively
> > short early boot period, with no scheduling, right?
>
> Yes, if there isn't agreement on this approach we can do that
> instead. Say:
>
> - Replace in_kernel_fpu with kernel_fpu_supported, with the opposite
> meaning (so that the initial value of false means "unsupported")
I'm not against simplifying the x86 FPU model to exclude IRQs-off
context (especially if it also micro-optimizes some of the key runtime
kernel-FPU primitives), but it has to be a full solution and we'll have
to see how complicated the EFI changes get.
Ie. without seeing the full cost-benefit balance it's hard to call this
in advance. Mind sending a full series that addresses the EFI case too?
Thanks,
Ingo
next prev parent reply other threads:[~2025-05-18 6:34 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-05-16 23:18 [PATCH 0/3] x86: Don't support kernel-mode FPU with hardirqs disabled Eric Biggers
2025-05-16 23:18 ` [PATCH 1/3] x86/fpu: Add fpu_save_state() for __save_processor_state() Eric Biggers
2025-05-16 23:18 ` [PATCH 2/3] x86/pm: Use fpu_save_state() in __save_processor_state() Eric Biggers
2025-05-16 23:18 ` [PATCH 3/3] x86/fpu: Don't support kernel-mode FPU when irqs_disabled() Eric Biggers
2025-05-17 7:09 ` Ingo Molnar
2025-05-17 18:39 ` Eric Biggers
2025-05-18 6:34 ` Ingo Molnar [this message]
2025-05-18 13:18 ` Ard Biesheuvel
2025-05-18 20:01 ` Eric Biggers
2025-05-19 8:05 ` Ingo Molnar
2025-05-19 9:49 ` Ard Biesheuvel
2025-05-19 12:57 ` Ingo Molnar
2025-05-19 13:50 ` Ard Biesheuvel
2025-05-20 7:42 ` Ingo Molnar
2025-05-17 1:30 ` [PATCH 0/3] x86: Don't support kernel-mode FPU with hardirqs disabled Eric Biggers
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