[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen master] x86/cpuid: Avoid unconditionally clobbering ITSC for guests
commit a5adcee740df2679cf6828535279d8f8cbe2eff1 Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> AuthorDate: Fri May 13 19:38:41 2016 +0100 Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> CommitDate: Tue May 17 15:54:49 2016 +0100 x86/cpuid: Avoid unconditionally clobbering ITSC for guests In general, Invariant TSC is not a feature which can be advertised to guests, because it cannot be guaranteed across migrate. domain_cpuid() goes so far as to deliberately clobber the feature flag under a number of circumstances. Because ITSC is absent from the static {pv,hvm}_featureset masks, c/s b648feff "xen/x86: Improvements to in-hypervisor cpuid sanity checks" caused ITSC to be unconditionally masked out. As an interim solution, include the hosts idea of ITSC along with the static {pv,hvm}_featureset when restricting the guests view of features. This causes the hardware domain, and VMs explicitly configured with ITSC and no-migrate to be offered ITSC (subject to hardware availability). Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> Reviewed-by: Jan Beulich <JBeulich@xxxxxxxx> Release-acked-by: Wei Liu <wei.liu2@xxxxxxxxxx> --- xen/arch/x86/hvm/hvm.c | 3 ++- xen/arch/x86/traps.c | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c index 7492030..5040a5c 100644 --- a/xen/arch/x86/hvm/hvm.c +++ b/xen/arch/x86/hvm/hvm.c @@ -3509,7 +3509,8 @@ void hvm_cpuid(unsigned int input, unsigned int *eax, unsigned int *ebx, break; case 0x80000007: - *edx &= hvm_featureset[FEATURESET_e7d]; + *edx &= (hvm_featureset[FEATURESET_e7d] | + (host_featureset[FEATURESET_e7d] & cpufeat_mask(X86_FEATURE_ITSC))); break; case 0x80000008: diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c index 0052ab8..1ef8401 100644 --- a/xen/arch/x86/traps.c +++ b/xen/arch/x86/traps.c @@ -1142,7 +1142,8 @@ void pv_cpuid(struct cpu_user_regs *regs) break; case 0x80000007: - d &= pv_featureset[FEATURESET_e7d]; + d &= (pv_featureset[FEATURESET_e7d] | + (host_featureset[FEATURESET_e7d] & cpufeat_mask(X86_FEATURE_ITSC))); break; case 0x80000008: -- generated by git-patchbot for /home/xen/git/xen.git#master _______________________________________________ Xen-changelog mailing list Xen-changelog@xxxxxxxxxxxxx http://lists.xensource.com/xen-changelog
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