linux-kernel - Re: [PATCH 6/7] mm/x86: Add missing pud helpers

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Date: Fri, 21 Jun 2024 19:36:30 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "linux-mm@...ck.org" <linux-mm@...ck.org>, "peterx@...hat.com"
	<peterx@...hat.com>, "Hansen, Dave" <dave.hansen@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
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	<willy@...radead.org>, "dave.hansen@...ux.intel.com"
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	<ying.huang@...el.com>, "x86@...nel.org" <x86@...nel.org>, "Williams, Dan J"
	<dan.j.williams@...el.com>
Subject: Re: [PATCH 6/7] mm/x86: Add missing pud helpers

On Fri, 2024-06-21 at 07:51 -0700, Dave Hansen wrote:
> 
> But, still, what if you take a Dirty=1,Write=1 pud and pud_modify() it
> to make it Dirty=1,Write=0?  What prevents that from being
> misinterpreted by the hardware as being a valid 1G shadow stack mapping?

Hmm, it looks like we could use an arch_check_zapped_pud() that does a warning
like arch_check_zapped_pte/pmd() too. Not that we had no use for one before
this.