Re: [PATCH 5/5] dax: always use _copy_mc_to_iter in dax_copy_to_iter

Vivek Goyal
2021-12-14T13:59:08Z

On Sun, Dec 12, 2021 at 06:48:05AM -0800, Dan Williams wrote:
> On Fri, Dec 10, 2021 at 6:05 AM Vivek Goyal <vgoyal@redhat.com> wrote:
> >
> > On Thu, Dec 09, 2021 at 07:38:28AM +0100, Christoph Hellwig wrote:
> > > While using the MC-safe copy routines is rather pointless on a virtual device
> > > like virtiofs,
> >
> > I was wondering about that. Is it completely pointless.
> >
> > Typically we are just mapping host page cache into qemu address space.
> > That shows as virtiofs device pfn in guest and that pfn is mapped into
> > guest application address space in mmap() call.
> >
> > Given on host its DRAM, so I would not expect machine check on load side
> > so there was no need to use machine check safe variant.
>
> That's a broken assumption, DRAM experiences multi-bit ECC errors.
> Machine checks, data aborts, etc existed before PMEM.

So we should use MC safe variant when loading from DRAM as well?
(If needed platoform support is there).

Vivek