linux-kernel - Re: [PATCH 3/3] x86, ras: Add mcsafe_memcpy() function to recover from machine checks

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Message-ID: <20151214095500.GA31573@gmail.com>
Date:	Mon, 14 Dec 2015 10:55:00 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	"Luck, Tony" <tony.luck@...el.com>, Borislav Petkov <bp@...en8.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-edac@...r.kernel.org,
	the arch/x86 maintainers <x86@...nel.org>,
	Jens Axboe <axboe@...com>,
	"Verma, Vishal L" <vishal.l.verma@...el.com>,
	Jeff Moyer <jmoyer@...hat.com>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...1.01.org>
Subject: Re: [PATCH 3/3] x86, ras: Add mcsafe_memcpy() function to recover
 from machine checks


* Dan Williams <dan.j.williams@...el.com> wrote:

> [ adding nvdimm folks ]
> 
> On Fri, Nov 27, 2015 at 2:16 AM, Ingo Molnar <mingo@...nel.org> wrote:
> >
> > * Luck, Tony <tony.luck@...el.com> wrote:
> >
> >> On Thu, Nov 12, 2015 at 08:53:13AM +0100, Ingo Molnar wrote:
> >> > > +extern phys_addr_t mcsafe_memcpy(void *dst, const void __user *src,
> >> > > +                         unsigned size);
> >> >
> >> > So what's the longer term purpose, where will mcsafe_memcpy() be used?
> >>
> >> The initial plan is to use this for file systems backed by NVDIMMs. They will
> >> have a large amount of memory, and we have a practical recovery path - return
> >> -EIO just like legacy h/w.
> >>
> >> We can look for other places in the kernel where we read large amounts of memory
> >> and have some idea how to recover if the memory turns out to be bad.
> >
> > I see, that's sensible!
> >
> > Thanks,
> >
> >         Ingo
> 
> Is that an "Acked-by"?  I'd like to pull this plus Vishal's
> gendisk-badblocks patches into a unified libnvdimm-error-handling
> branch.  We're looking to have v4.5 able to avoid or survive nvdimm
> media errors through the pmem driver and DAX paths.

So there was some feedback for v2 as well - I'd like to see v3 before an Acked-by.

But yeah, this is progressing in the right direction, and I suspect it's a 
relatively urgent feature from an nvdimm POV?

Thanks,

	Ingo
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