linux-kernel - Re: [PATCH] mm/hwpoison: Clear PRESENT bit for kernel 1:1 mappings of poison pages

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Date:   Thu, 22 Jun 2017 11:39:05 +0200
From:   Borislav Petkov <bp@...e.de>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>, x86@...nel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Yazen Ghannam <yazen.ghannam@....com>
Subject: Re: [PATCH] mm/hwpoison: Clear PRESENT bit for kernel 1:1 mappings
 of poison pages

On Wed, Jun 21, 2017 at 10:47:40AM -0700, Luck, Tony wrote:
> I would if I could work out how to use it. From reading the manual
> page there seem to be a few options to this, but none of them appear
> to just drop a specific address (apart from my own). :-(

$ git send-email --to ... --cc ... --cc ... --suppress-cc=all ...

That should send only to the ones you have in --to and --cc and suppress
the rest.

Do a

$ git send-email -v --dry-run --to ... --cc ... --cc ... --suppress-cc=all ...

to see what it is going to do.

> I'd assume that other X86 implementations would face similar issues (unless
> they have extremely cautious pre-fetchers and/or no speculation).
> 
> I'm also assuming that non-X86 architectures that do recovery may want this
> too ... hence hooking the arch_unmap_kpfn() function into the generic
> memory_failure() code.

Which means that you could move the function to generic
mm/memory_failure.c code after making the decoy_addr computation
generic.

I'd still like to hear some sort of confirmation from other
vendors/arches whether it makes sense for them too, though.

I mean, if they don't do speculative accesses, then it probably doesn't
matter even - the page is innacessible anyway but still...

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--