[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [v3][PATCH 1/1] xen:vtd: missing RMRR mapping while share EPT
Jan Beulich wrote on 2014-07-25: >>>> On 24.07.14 at 19:12, <kevin.tian@xxxxxxxxx> wrote: >>>> From: Chen, Tiejun >>> Sent: Thursday, July 24, 2014 4:00 AM >>> >>> intel_iommu_map_page() does nothing if VT-d shares EPT page table. >>> So rmrr_identity_mapping() never create RMRR mapping but in some >>> cases like some GFX drivers it still need to access RMRR. >> >> this is not accurate. as long as RMRR is reported, it's always >> necessary to have the identity mapping there, not just needed in >> SOME CASES. :-) > > Actually (as also said before) I think "in some cases" is quite correct: > There's no guarantee that a device will actually access the region(s) > an RMRR may specify for it. A particular example would be the USB case > where iiuc these regions are needed only until legacy mode emulation gets > turned off. Yes, even for Intel GFX, the RMRR is never really accessed. So we never saw any issue even without this patch. > > Jan Best regards, Yang _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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