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Date:   Thu, 8 Nov 2018 12:38:17 +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 01/23] x86/fpu: Use ULL for shift in
 xfeature_uncompacted_offset()
Message-ID: <20181108113817.GB7543@zn.tnic>
References: <20181107194858.9380-1-bigeasy@linutronix.de>
 <20181107194858.9380-2-bigeasy@linutronix.de>
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On Wed, Nov 07, 2018 at 08:48:36PM +0100, Sebastian Andrzej Siewior wrote:
> The xfeature mask is 64bit so a shift from a number to its mask should
> have LL prefix or else nr > 31 will be lost. This is not a problem now
> but should XFEATURE_MASK_SUPERVISOR gain a bit >31 then this check won't
> catch it.
> 
> Add a ULL suffix so >31bit number will be properly shifted.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  arch/x86/kernel/fpu/xstate.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
> index 87a57b7642d36..9dc0a2c8c2755 100644
> --- a/arch/x86/kernel/fpu/xstate.c
> +++ b/arch/x86/kernel/fpu/xstate.c
> @@ -444,7 +444,7 @@ static int xfeature_uncompacted_offset(int xfeature_nr)
>  	 * format. Checking a supervisor state's uncompacted offset is
>  	 * an error.
>  	 */
> -	if (XFEATURE_MASK_SUPERVISOR & (1 << xfeature_nr)) {
> +	if (XFEATURE_MASK_SUPERVISOR & (1ULL << xfeature_nr)) {

Or simply BIT_ULL(xfeature_nr).

-- 
Regards/Gruss,
    Boris.

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