linux-kernel - Re: [PATCH v6 3/6] mce: fix set_mce_nospec to always unmap the whole page

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Date:   Tue, 22 Mar 2022 01:44:10 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Jane Chu <jane.chu@...cle.com>
Cc:     david@...morbit.com, djwong@...nel.org, dan.j.williams@...el.com,
        hch@...radead.org, vishal.l.verma@...el.com, dave.jiang@...el.com,
        agk@...hat.com, snitzer@...hat.com, dm-devel@...hat.com,
        ira.weiny@...el.com, willy@...radead.org, vgoyal@...hat.com,
        linux-fsdevel@...r.kernel.org, nvdimm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org
Subject: Re: [PATCH v6 3/6] mce: fix set_mce_nospec to always unmap the whole
 page

On Sat, Mar 19, 2022 at 12:28:30AM -0600, Jane Chu wrote:
> Mark poisoned page as not present, and to reverse the 'np' effect,
> restate the _PAGE_PRESENT bit. Please refer to discussions here for
> reason behind the decision.
> https://lore.kernel.org/all/CAPcyv4hrXPb1tASBZUg-GgdVs0OOFKXMXLiHmktg_kFi7YBMyQ@mail.gmail.com/

I think it would be good to summarize the conclusion here instead of
just linking to it.

> +static int _set_memory_present(unsigned long addr, int numpages)
> +{
> +	return change_page_attr_set(&addr, numpages, __pgprot(_PAGE_PRESENT), 0);
> +}

What is the point of this trivial helper with a single caller?