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Subject: Re: [PATCH 1/2] x86: mm: ptdump: Calculate effective permissions
 correctly
To:     Steven Price <steven.price@arm.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Andy Lutomirski <luto@kernel.org>,
        Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>, x86@kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
References: <20200521152308.33096-1-steven.price@arm.com>
 <20200521152308.33096-2-steven.price@arm.com>
From:   Jan Beulich <jbeulich@suse.com>
Message-ID: <5a7fc0d5-14c5-d263-daf1-bf81da30d91e@suse.com>
Date:   Wed, 27 May 2020 17:15:17 +0200
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On 21.05.2020 17:23, Steven Price wrote:
> By switching the x86 page table dump code to use the generic code the
> effective permissions are no longer calculated correctly because the
> note_page() function is only called for *leaf* entries. To calculate the
> actual effective permissions it is necessary to observe the full
> hierarchy of the page tree.
> 
> Introduce a new callback for ptdump which is called for every entry and
> can therefore update the prot_levels array correctly. note_page() can
> then simply access the appropriate element in the array.
> 
> Reported-by: Jan Beulich <jbeulich@suse.com>
> Fixes: 2ae27137b2db ("x86: mm: convert dump_pagetables to use walk_page_range")
> Signed-off-by: Steven Price <steven.price@arm.com>

This (with the later correction) and the 2nd patch
Tested-by: Jan Beulich <jbeulich@suse.com>

It allowed me to go and finally find why under Xen there was still
a single W+X mapping left - another bug, another patch.

Thanks, Jan