| Message ID | 1463417955-4258-1-git-send-email-andrew.cooper3@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
>>> On 16.05.16 at 18:59, <andrew.cooper3@citrix.com> wrote: > 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@citrix.com> Reviewed-by: Jan Beulich <jbeulich@suse.com>
On Mon, May 16, 2016 at 05:59:15PM +0100, Andrew Cooper wrote: > 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@citrix.com> Release-acked-by: Wei Liu <wei.liu2@citrix.com>
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:
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@citrix.com> --- CC: Jan Beulich <JBeulich@suse.com> CC: Wei Liu <wei.liu2@citrix.com> --- xen/arch/x86/hvm/hvm.c | 3 ++- xen/arch/x86/traps.c | 3 ++- 2 files changed, 4 insertions(+), 2 deletions(-)