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Date:   Wed, 12 Dec 2018 18:11:29 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        Andy Lutomirski <luto@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        kvm@vger.kernel.org, "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Rik van Riel <riel@surriel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>
Subject: Re: [PATCH 11/29] x86/fpu: Always init the `state' in fpu__clear()
Message-ID: <20181212171129.GD6653@zn.tnic>
References: <20181128222035.2996-1-bigeasy@linutronix.de>
 <20181128222035.2996-12-bigeasy@linutronix.de>
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On Wed, Nov 28, 2018 at 11:20:17PM +0100, Sebastian Andrzej Siewior wrote:
> fpu__clear() only initializes the `state' if the FPU is present. This
> initialisation is also required for the FPU-less system and takes place
> math_emulate(). Since fpu__initialize() only performs the initialization
> if ->initialized is zero it does not matter that it is invoked each time
> an opcode is emulated. It makes the removal of ->initialized easier if
> the struct is also initialized in FPU-less case at the same time.
> 
> Move fpu__initialize() before the FPU check so it is also performed in
> FPU-less case.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  arch/x86/include/asm/fpu/internal.h | 1 -
>  arch/x86/kernel/fpu/core.c          | 5 ++---
>  arch/x86/math-emu/fpu_entry.c       | 3 ---
>  3 files changed, 2 insertions(+), 7 deletions(-)

...

> diff --git a/arch/x86/math-emu/fpu_entry.c b/arch/x86/math-emu/fpu_entry.c
> index 9e2ba7e667f61..a873da6b46d6b 100644
> --- a/arch/x86/math-emu/fpu_entry.c
> +++ b/arch/x86/math-emu/fpu_entry.c
> @@ -113,9 +113,6 @@ void math_emulate(struct math_emu_info *info)
>  	unsigned long code_base = 0;
>  	unsigned long code_limit = 0;	/* Initialized to stop compiler warnings */
>  	struct desc_struct code_descriptor;
> -	struct fpu *fpu = &current->thread.fpu;
> -
> -	fpu__initialize(fpu);

Ok, you're removing it here but where is the FPU going to be initialized
now in the FPU-less case?

IOW, it is not clear to me where fpu__clear() get called for the FPU
emulation case now...

-- 
Regards/Gruss,
    Boris.

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