>>> On 15.01.15 at 16:06, <andrew.coop...@citrix.com> wrote: > On 15/01/15 14:53, Jan Beulich wrote: >>>>> On 15.01.15 at 15:14, <jbeul...@suse.com> wrote: >>> But I think I made a wrong assumption above regarding the >>> guest size: test-amd64-i386-xl-win7-amd64 produces a 64-bit >>> guest with a 32-bit tool stack, so the crucial part of all the >>> tests failing is not the guest's bitness, but tool stack's. So I'll >>> next look into which of the three feature flags might be off >>> when inspected from a 32-bit Dom0, as I now suspect that the >>> guest simply doesn't get its CPUID bits correctly set up by a >>> 32-bit Dom0 (i.e. the patch might just have uncovered a latent >>> bug). >> And there you go: The hypervisor deliberately clears the >> syscall feature flag for 32-bit PV guests on non-AMD CPUs, and >> hardware appears to do so too when CPUID gets executed from >> a non-64-bit CS (i.e. no matter whether you execute raw or >> "Xen-ified" CPUID there, you won't see that flag set). Yet 64-bit >> guests won't be bothered to check whether the flag is enabled, >> as x86-64 requires the feature to be there. > > As AMD had supported syscall in 32bit systems for a long time, I presume > it is only Intel where the feature bit in cpuid changes depending on cs.L
Sure. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
