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

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

[Dan Williams]

[ adding nvdimm folks ]

On Fri, Nov 27, 2015 at 2:16 AM, Ingo Molnar <mingo@kernel.org> wrote:
>
> * Luck, Tony <tony.luck@intel.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.

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

[Luck, Tony]

> 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.

I'm making a V2 that fixes some build errors for 32-bit and addresses other commentary
from the community. Perhaps a couple more days before I finish it up ready to post.

-Tony

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

[Ingo Molnar]

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

> [ adding nvdimm folks ]
> 
> On Fri, Nov 27, 2015 at 2:16 AM, Ingo Molnar <mingo@kernel.org> wrote:
> >
> > * Luck, Tony <tony.luck@intel.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