On 12/12/16 23:47, Tamas K Lengyel wrote: > >> It works on x86 because, IIRC, you do a software page table walking. >> Although, I don't think you have particular write/read access checking on >> x86. > I don't recall there being any software page walking being involved on > x86. Why would that be needed? On x86 we get the guest physical > address recorded by the CPU automatically. AFAIK in case the pagetable > was unaccessible for the translation of a VA, we would get an event > with the pagetable's PA and the type of event that generated it (ie. > reading during translation).
x86 provides no mechanism to have hardware translate an address in a separate context. Therefore, all translations which are necessary need to be done in hardware. Newer versions of VT-x/SVM may provide additional information on a vmexit, which include a guest physical address relevant to the the reason for the vmexit. Xen will attempt to proactively use this information to avoid a software pagewalk, but can always fall back to the software method if needs be. I presume ARM has always relied on hardware support for translation, and has no software translation support? I presume therefore that translations only work when in current context? ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
