[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] x86/vtd: fix IOMMU share PT destruction path
>>> On 09.10.18 at 14:57, <roger.pau@xxxxxxxxxx> wrote: > On Tue, Oct 09, 2018 at 12:22:34PM +0100, Paul Durrant wrote: >> > -----Original Message----- >> > From: Wei Liu [mailto:wei.liu2@xxxxxxxxxx] >> > Sent: 09 October 2018 11:42 >> > To: xen-devel@xxxxxxxxxxxxxxxxxxxx >> > Cc: Jan Beulich <JBeulich@xxxxxxxx>; Roger Pau Monne >> > <roger.pau@xxxxxxxxxx>; Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Wei Liu >> > <wei.liu2@xxxxxxxxxx>; Kevin Tian <kevin.tian@xxxxxxxxx> >> > Subject: [PATCH] x86/vtd: fix IOMMU share PT destruction path >> > >> > Commit 2916951c1 ("mm / iommu: include need_iommu() test in >> > iommu_use_hap_pt()") included need_iommu() in iommu_use_hap_pt and >> > 91d4eca7add (" mm / iommu: split need_iommu() into has_iommu_pt() and >> > need_iommu_pt_sync()") made things finer grain by spliting need_iommu >> > into three states. >> > >> > The destruction path can't use iommu_use_hap_pt because at the point >> > platform op is called, IOMMU is already switched to disabled state and >> > the shared PT test would always be false. >> > >> >> This is VT-d specific and the issue could affect AMD too. Can't you just > switch round the call to teardown and setting IOMMU_status_disabled in > xen/drivers/passthrough/iommu.c:iommu_teardown()? > > AMD doesn't support shared page tables so far, but in order to avoid > having to debug this again if AMD ever gains support for shared page > tables I think switching the order in iommu_teardown might be better. I think we've pretty much ruled out AMD ever re-gaining such sharing functionality. In fact I thought we had settled that the dead code relating to this functionality could be ripped out, if anyone could carve out the time needed for doing so. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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