linux-kernel - Re: [PATCH v3] x86/boot: Avoid writing to cr4 twice in startup

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Message-ID: <1f809e9d-5383-469d-8c31-10f8230b79b8@zytor.com>
Date: Tue, 15 Jul 2025 13:31:35 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Khalid Ali <khaliidcaliy@...il.com>, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com
Cc: x86@...nel.org, ardb@...nel.org, ubizjak@...il.com, brgerst@...il.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] x86/boot: Avoid writing to cr4 twice in startup_64()

On 2025-07-15 11:16, Khalid Ali wrote:
> From: Khalid Ali <khaliidcaliy@...il.com>
> 
> When Initializing cr4 bit PSE and PGE, cr4 is written twice for	
> each bit. This is redundancy.
> 
> Instead, set both bits first and write CR4 once, avoiding redundant
> writes. This makes consistent with cr0 writes, which is set bits and
> write once.
> 
> Signed-off-by: Khalid Ali <khaliidcaliy@...il.com>

In case this wasn't obvious, this is:

Nacked-by: H. Peter Anvin (Intel) <hpa@...or.com>

... with extreme prejudice.

	-hpa