[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
On 2014/7/25 16:36, Jan Beulich wrote: On 25.07.14 at 10:24, <yang.z.zhang@xxxxxxxxx> wrote:Jan Beulich wrote on 2014-07-25:On 24.07.14 at 19:12, <kevin.tian@xxxxxxxxx> wrote: From: Chen, TiejunSent: 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 getsturned off. Yes, even for Intel GFX, the RMRR is never really accessed. So we never saw any issue even without this patch.So then what's the patch good for? If it's just addressing a theoretical No, this is not a theoretical problem.I already reply to Yang, on BDW windows GFX driver really accesses this range now. Without this patch, the blue screen appears. Tiejun issue, then this supports my intention to commit it only when the other (theoretical only) problem also gets taken care of. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
|
Lists.xenproject.org is hosted with RackSpace, monitoring our |