On 14/06/2016 07:01, Chao Peng wrote: >> > >> > Which are the CPUID leaves for which KVM_GET_SUPPORTED_CPUID is not >> > stateless? I cannot find any. > I have though leaf 0xd, sub leaf 1 is not stateless, as the size of > xsave buffer(EBX) is based on XCR0 | IA32_XSS. But after looking KVM > code more carefully, seems I was wrong. The code calculates EBX with the > host xcr0 but not guest xcr0, nor guest IA32_XSS (not sure if this is > the correct behavior), so it can always returns constant data on a > certain machine.
Indeed, KVM computes the correct value at runtime, but KVM_GET_SUPPORTED_CPUID runs before there is a value for guest XCR0 or guest IA32_XSS. Thanks, I've queued the patch for QEMU 2.7. Paolo
