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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH for-4.12] arm/p2m: do not invalidate p2m root if it is shared with IOMMU
On 29.01.19 17:17, Julien Grall wrote: No we don't have to. I mean, EPAM systems as a XEN based virtualization solution provider have to handle that issue. They have been lucky to see this working even on baremetal. Set/Way operations have been dropped from Linux for a long time, so I really can't see why a proprietary driver is still using them. I guess there were some performance concerns. And they are really lucky, so they did not face related issues on baremetal. I think the policy for Set/Way operations is correct in Xen. This works to avoid breaking basic case but the most complex one are going to break. Maybe it worth to get a notification from XEN, i.e. WARN_ONCE, saying that Set/Way cache operations are undesirable in VM and will lead to the system performance drop, or even instability in case of IOMMU sharing p2m with CPU. This might save days of debugging to XEN on ARM users. You solution is only delaying the real fix I would not say it is delaying the fix, but allows us to have a functional system until we get that fix. (i.e removing Set/Way operation from the software). So here the best solution is to go to the vendor and ask them to fix their software. Actually escalation the issue to the vendor is one of our next steps here. -- Sincerely, Andrii Anisov. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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