[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v2] x86/hvmloader: round up memory BAR size to 4K
On Mon, Jan 20, 2020 at 05:10:33PM +0100, Jan Beulich wrote: > On 17.01.2020 12:08, Roger Pau Monne wrote: > > When placing memory BARs with sizes smaller than 4K multiple memory > > BARs can end up mapped to the same guest physical address, and thus > > won't work correctly. > > Thinking about it again, aren't you fixing one possible case by > breaking the opposite one: What you fix is when the two distinct > BARs (of the same or different devices) map to distinct MFNs > (which would have required a single GFN to map to both of these > MFNs). But don't you, at the same time, break the case of two > BARs (perhaps, but not necessarily, of the same physical device) > mapping both to the same MFN, i.e. requiring to have two distinct > GFNs map to one MFN? (At least for the moment I can't see a way > for hvmloader to distinguish the two cases.) IMO we should force all BARs to be page-isolated by dom0 (since Xen doesn't have the knowledge of doing so), but I don't see the issue with having different gfns pointing to the same mfn. Is that a limitation of paging? I think you can map a grant multiple times into different gfns, which achieves the same AFAICT. Roger. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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