linux-kernel - Re: [PATCH v3 3/3] x86: Zap TOP_OF_KERNEL_STACK_PADDING on x86

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Message-ID: <1106B557-4AA2-410F-A990-C0C3BB7E675B@zytor.com>
Date: Fri, 21 Mar 2025 01:14:54 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Xin Li <xin@...or.com>, Brian Gerst <brgerst@...il.com>
CC: linux-kernel@...r.kernel.org, luto@...nel.org, tglx@...utronix.de,
        mingo@...nel.org, bp@...en8.de, dave.hansen@...ux.intel.com,
        x86@...nel.org, peterz@...radead.org
Subject: Re: [PATCH v3 3/3] x86: Zap TOP_OF_KERNEL_STACK_PADDING on x86_64

On March 20, 2025 10:47:25 PM PDT, Xin Li <xin@...or.com> wrote:
>On 3/19/2025 12:17 PM, Brian Gerst wrote:
>> I'm not sure it's worth fully removing TOP_OF_KERNEL_STACK_PADDING for
>> 64-bit if it results in needing separate definitions of
>> task_top_of_stack().  Leaving it at zero is fine.  The other changes
>> are fine though.
>
>Let's leave it to x86 maintainers ;-)
>
>But to me, TOP_OF_KERNEL_STACK_PADDING no longer makes sense on 64-bit,
>and it makes it simpler to remove it.  On the other side, 32-bit is to
>be zapped...
>
>Thanks!
>    Xin
>

For what it's worth, it was there as 0 before the FRED changes, so ...