From: Dave Hansen <dave.hansen@intel.com>
To: Ingo Molnar <mingo@kernel.org>, Eric Biggers <ebiggers@kernel.org>
Cc: x86@kernel.org, linux-crypto@vger.kernel.org,
linux-kernel@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
Ben Greear <greearb@candelatech.com>,
Xiao Liang <shaw.leon@gmail.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
"Jason A . Donenfeld" <Jason@zx2c4.com>,
"Bae, Chang Seok" <chang.seok.bae@intel.com>
Subject: Re: [RFC PATCH v2] x86/fpu: make kernel-mode FPU reliably usable in softirqs
Date: Wed, 5 Mar 2025 08:55:12 -0800 [thread overview]
Message-ID: <b6a80f6d-8469-429d-b03a-8fa71a33046b@intel.com> (raw)
In-Reply-To: <Z8gUYamgBr4M5ZaB@gmail.com>
On 3/5/25 01:07, Ingo Molnar wrote:>> Alternatives considered:
>> - Make kernel-mode FPU sections fully preemptible. This would require
>> growing task_struct by another struct fpstate which is more than 2K.
>
> So that's something that will probably happen once the kernel is built
> using APX anyway?
I was expecting that building the kernel with APX would be very
different than a kernel_fpu_begin(). We don't just need *one* more save
area for APX registers: we need a stack, just like normal GPRs.
We'd effectively need to enlarge pt_regs and fix up things like
PUSH_AND_CLEAR_REGS to save the APX registers in addition to the good
old GPRs before calling C code.
That's what I was thinking at least. Did folks have more clever ideas?
next prev parent reply other threads:[~2025-03-05 16:54 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-04 20:49 [RFC PATCH v2] x86/fpu: make kernel-mode FPU reliably usable in softirqs Eric Biggers
2025-03-05 9:07 ` Ingo Molnar
2025-03-05 16:55 ` Dave Hansen [this message]
2025-03-05 17:37 ` Ingo Molnar
2025-03-05 18:04 ` Dave Hansen
2025-03-05 18:13 ` Ingo Molnar
2025-03-05 21:22 ` David Laight
2025-03-05 17:39 ` Eric Biggers
2025-03-05 18:09 ` Ingo Molnar
2025-03-05 20:30 ` Eric Biggers
2025-03-06 11:42 ` Ingo Molnar
2025-03-06 12:09 ` Peter Zijlstra
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