linux-kernel - Re: [PATCH] x86/mm: fix lookup_address() to handle physical memory holes in direct mapping

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Message-ID: <25478bbd92a0dacb6d52d7ffd214374e151a9338.camel@intel.com>
Date: Mon, 1 Jul 2024 19:13:30 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "jgross@...e.com" <jgross@...e.com>, "luto@...nel.org" <luto@...nel.org>,
	"bp@...en8.de" <bp@...en8.de>, "dave.hansen@...ux.intel.com"
	<dave.hansen@...ux.intel.com>, "peterz@...radead.org" <peterz@...radead.org>,
	"mingo@...hat.com" <mingo@...hat.com>, "tglx@...utronix.de"
	<tglx@...utronix.de>, "ashish.kalra@....com" <ashish.kalra@....com>
CC: "x86@...nel.org" <x86@...nel.org>, "mhklinux@...look.com"
	<mhklinux@...look.com>, "Rodel, Jorg" <jroedel@...e.de>, "hpa@...or.com"
	<hpa@...or.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "thomas.lendacky@....com"
	<thomas.lendacky@....com>, "kirill.shutemov@...ux.intel.com"
	<kirill.shutemov@...ux.intel.com>, "peterx@...hat.com" <peterx@...hat.com>,
	"linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>
Subject: Re: [PATCH] x86/mm: fix lookup_address() to handle physical memory
 holes in direct mapping

On Mon, 2024-07-01 at 13:59 -0500, Kalra, Ashish wrote:
> 
> Then what is the caller supposed to do in this case ?
> 
> As the return from lookup_address() is non-NULL in this case, accessing it
> causes a fatal #PF.
> 
> Is the caller supposed to add the check for a valid PTE using pte_none(*pte) ?

I did a quick look at the callers, and some do their own check for pte_none().
But some don't. Some also assume the return can't be NULL.

Can you elaborate on your goal for this change? Just a cleanup?