> -----Original Message----- > From: Jan Beulich <jbeul...@suse.com> > Sent: 27 November 2019 15:26 > To: Durrant, Paul <pdurr...@amazon.com> > Cc: Kevin Tian <kevin.t...@intel.com>; xen-devel@lists.xenproject.org; > Andrew Cooper <andrew.coop...@citrix.com>; Roger Pau Monné > <roger....@citrix.com>; Wei Liu <w...@xen.org> > Subject: Re: [Xen-devel] [PATCH] x86 / iommu: set up a scratch page in the > quarantine domain > > On 27.11.2019 16:18, Durrant, Paul wrote: > >> -----Original Message----- > >> From: Tian, Kevin <kevin.t...@intel.com> > >> Sent: 25 November 2019 08:22 > >> To: Durrant, Paul <pdurr...@amazon.com>; xen-devel@lists.xenproject.org > >> Cc: Jan Beulich <jbeul...@suse.com>; Andrew Cooper > >> <andrew.coop...@citrix.com>; Wei Liu <w...@xen.org>; Roger Pau Monné > >> <roger....@citrix.com> > >> Subject: RE: [PATCH] x86 / iommu: set up a scratch page in the > quarantine > >> domain > >> > >>> From: Paul Durrant [mailto:pdurr...@amazon.com] > >>> Sent: Wednesday, November 20, 2019 8:09 PM > >>> > >>> This patch introduces a new iommu_op to facilitate a per- > implementation > >>> quarantine set up, and then further code for x86 implementations > >>> (amd and vtd) to set up a read/wrote scratch page to serve as the > >> source/ > >>> target for all DMA whilst a device is assigned to dom_io. > >>> > >>> The reason for doing this is that some hardware may continue to re-try > >>> DMA, despite FLR, in the event of an error. Having a scratch page > mapped > >>> will allow pending DMA to drain and thus quiesce such buggy hardware. > >> > >> then there is no diagnostics at all since all faults are quiescent > now... > >> why do we want to support such buggy hardware? Is it better to make > >> it an default-off option since buggy is supposed to niche case? > > > > I guess it could be a command line option... perhaps making the new > > 'iommu=quarantine' boolean into something more complex, but I'm not > > sure it's really worth it. Perhaps a compile time option would be > > better? > > Yet another option: How about installing the scratch page mappings > only after a (handful of) IOMMU faults? But of course there was the > related earlier question of whether indeed our turning off of bus > mastering doesn't already help silencing the faults.
No. Unfortunately the h/w has zero tolerance for some faults. Paul > > Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
