linux-kernel - Re: [PATCH 17/23] x86/fpu: Eager switch PKRU state

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Message-ID: <1d4b7b5c-9c3d-1ef5-3336-b7945b7978d4@redhat.com>
Date:   Thu, 8 Nov 2018 12:12:52 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-kernel@...r.kernel.org
Cc:     x86@...nel.org, Andy Lutomirski <luto@...nel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        kvm@...r.kernel.org, "Jason A. Donenfeld" <Jason@...c4.com>,
        Rik van Riel <riel@...riel.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [PATCH 17/23] x86/fpu: Eager switch PKRU state

On 07/11/2018 20:48, Sebastian Andrzej Siewior wrote:
> index 375226055a413..5b33985d9f475 100644
> --- a/arch/x86/kernel/fpu/xstate.c
> +++ b/arch/x86/kernel/fpu/xstate.c
> @@ -811,7 +811,7 @@ void fpu__resume_cpu(void)
>   *
>   * Note: does not work for compacted buffers.
>   */

The comment is wrong, which was already the case before but it becomes a
bit more important if the function is used outside its module.

However, why not use get_xsave_addr?  I don't see why it is important to
skip the checks, and if it is it probably deserves a comment. "Raw" and
double underscores in the function name is scary...

Paolo

> -static void *__raw_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
> +void *__raw_xsave_addr(struct xregs_state *xsave, int xfeature_nr)
>  {
>  	if (!xfeature_enabled(xfeature_nr)) {
>  		WARN_ON_FPU(1);