Re: [PATCHV2 3/3] x86, ras: Add mcsafe_memcpy() function to recover from machine checks

From: Andy Lutomirski
Date: Fri Dec 11 2015 - 17:27:19 EST

On Fri, Dec 11, 2015 at 2:20 PM, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> On Fri, Dec 11, 2015 at 2:17 PM, Luck, Tony <tony.luck@xxxxxxxxx> wrote:
>>> Also, would it be more straightforward if the mcexception landing pad
>>> looked up the va -> pa mapping by itself? Or is that somehow not
>>> reliable?
>> If we did get all the above right, then we could have
>> target use virt_to_phys() to convert to physical ...
>> I don't see that this part would be a problem.
> virt_to_phys() implies a linear address. In the case of the use in
> the pmem driver we'll be using an ioremap()'d address off somewherein
> vmalloc space.

There's always slow_virt_to_phys.

Note that I don't fundamentally object to passing the pa to the fixup
handler. I just think we should try to disentangle that from figuring
out what exactly the failure was.

Also, are there really PCOMMIT-capable CPUs that still forcibly
broadcast MCE? If, so, that's unfortunate.

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