On 09/04/15 09:51, David Vrabel wrote: > On 08/04/15 20:44, Andrew Cooper wrote: >> Intead of clobbering DMAR -> XMAR and back, clobber to RMAD instead. This >> means that changing the signature does not alter the checksum, which allows >> the clobbering/unclobbering to be peformed atomically and idempotently, which >> is an advantage on the kexec path which can reenter acpi_dmar_reinstate(). > Could RMAD be specified as a real table in the future? Does the > clobbered name have to start with X to avoid future conflicts? > > David
I am not aware of any restrictions imposed by the APCI spec. Any clobbered signature is potentially a real table in the future. This DMAR clobbering was introduced by 83904107a33c9badc34ecdd1f8ca0f9271e5e370 which claims that the dom0 VT-d driver was capable of playing with the IOMMU(s) while Xen was also using them. An alternative approach might be to leave the DMAR table alone and sprinkle some iomem_deny_access() around to forcibly prevent dom0 from playing. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
