From: Ingo Molnar <mingo@kernel.org>
To: Benjamin Berg <benjamin@sipsolutions.net>
Cc: linux-arch@vger.kernel.org, linux-um@lists.infradead.org,
x86@kernel.org, briannorris@chromium.org,
linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com
Subject: Re: [PATCH 3/3] x86: avoid copying dynamic FP state from init_task
Date: Wed, 26 Feb 2025 14:23:03 +0100 [thread overview]
Message-ID: <Z78Vt8yCcPrFQeqo@gmail.com> (raw)
In-Reply-To: <159a83bf5457edbabcc1e88ee5ab98cf58ca6cb0.camel@sipsolutions.net>
* Benjamin Berg <benjamin@sipsolutions.net> wrote:
> > Note that this patch, while it still applies cleanly, crashes/hangs
> > the x86-64 defconfig kernel bootup in the early boot phase in a KVM
> > guest bootup.
>
> Oh, outch. It seems that arch_task_struct_size can actually become
> smaller than sizeof(init_task) if the CPU does not have certain
> features.
>
> See fpu__init_task_struct_size, which does:
>
> int task_size = sizeof(struct task_struct);
> task_size -= sizeof(current->thread.fpu.__fpstate.regs);
> task_size += fpu_kernel_cfg.default_size;
>
> I'll submit a new version of the patch and then also switch to use
> memcpy_and_pad.
Thank you!
Ingo
prev parent reply other threads:[~2025-02-26 13:23 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-17 20:27 [PATCH 0/3] KASAN fix for arch_dup_task_struct (x86, um) Benjamin Berg
2024-12-17 20:27 ` [PATCH 1/3] vmlinux.lds.h: remove entry to place init_task onto init_stack Benjamin Berg
2024-12-17 20:27 ` [PATCH 2/3] um: avoid copying FP state from init_task Benjamin Berg
2025-01-20 13:36 ` Thomas Weißschuh
2024-12-17 20:27 ` [PATCH 3/3] x86: avoid copying dynamic " Benjamin Berg
2025-02-26 13:08 ` Ingo Molnar
2025-02-26 13:19 ` Benjamin Berg
2025-02-26 13:23 ` Ingo Molnar [this message]
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