Re: [PATCH v9 0/10] iommu/vt-d: Fix intel vt-d faults in kdump kernel

Dave Young
2015-05-12T05:57:23Z

On 05/11/15 at 12:11pm, Joerg Roedel wrote:
> On Thu, May 07, 2015 at 09:56:00PM +0800, Dave Young wrote:
> > Joreg, I can not find the last reply from you, so just reply here about
> > my worries here.
> >
> > I said that the patchset will cause more problems, let me explain about
> > it more here:
> >
> > Suppose page table was corrupted, ie. original mapping iova1 -> page 1
> > it was changed to iova1 -> page 2 accidently while crash happening,
> > thus future dma will read/write page 2 instead page 1, right?
>
> When the page-table is corrupted then it is a left-over from the old
> kernel. When the kdump kernel boots the situation can at least not get
> worse. For the page tables it is also hard to detect wrong mappings (if
> this would be possible the hardware could already do it), so any checks
> we could do there are of limited use anyway.

Joerg, since both of you guys do not think it is a problem I will object it
any more though I still do not like reusing the old page tables. So let's
leave it as a future issue.

Thanks
Dave