>>> On 19.04.17 at 16:17, <andrew.coop...@citrix.com> wrote: > On 19/04/17 15:06, Jan Beulich wrote: >>>>> On 19.04.17 at 15:49, <andrew.coop...@citrix.com> wrote: >>> If a PV kernel is aware of UMIP and turns UMIP on, #GPs from userspace >>> should be bounced to the kernel, and #GPs from kernel space (as it is >>> ring-deprivileged) must be emulated and execute successfully. >>> >>> If Xen is using UMIP to protect itself, it needs to emulate and fake up >>> the information to both guest userspace and kernelspace. >>> >>> If both Xen and the PV kernel turn on UMIP, Xen needs to bounce >>> userspace #GPs to the guest kernel, and fake up information for the >>> guest kernel. >> I disagree in one point: If the guest kernel enabled UMIP, it being >> PV it should take care not to execute any of the covered insns (it >> has no use for them anyway). I see no reason to emulate anything >> in that case - emulation is needed only to keep _unaware_ >> environments working. > > That will involve someone ensuring that new PVops get introduced and used. > > Amongst other things, the current Linux doublefault handler uses sgdt.
But a PV guest would never get to see a #DF. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
