On 8/4/21 7:09 PM, Daniel P. Berrangé wrote: > We currently query the host MSRs to determine if TSC scaling is > supported. This works OK when running privileged and can open > the /dev/cpu/0/msr. When unprivileged we fallback to querying > MSRs from /dev/kvm. This is incorrect because /dev/kvm only > reports accurate info for MSRs that are valid to use from inside > a guest. The TSC scaling support MSR is not, thus we always end > up reporting lack of TSC scaling when unprivileged. > > The solution to this is easy, because KVM can directly report > whether TSC scaling is available, which matches what QEMU will > do at startup. > > https://gitlab.com/libvirt/libvirt/-/issues/188 Perhaps, Closes: https://gitlab.com/... ? > Reported-by: Roman Mohr <rmohr@xxxxxxxxxx> > Signed-off-by: Daniel P. Berrangé <berrange@xxxxxxxxxx> > --- > src/util/virhostcpu.c | 19 +++++++------------ > 1 file changed, 7 insertions(+), 12 deletions(-) > > diff --git a/src/util/virhostcpu.c b/src/util/virhostcpu.c > index 7aa92ad11d..f140610b47 100644 > --- a/src/util/virhostcpu.c > +++ b/src/util/virhostcpu.c > @@ -1349,11 +1349,10 @@ virHostCPUGetMSR(unsigned long index, > virHostCPUTscInfo * > virHostCPUGetTscInfo(void) > { > - virHostCPUTscInfo *info; > + g_autofree virHostCPUTscInfo *info = g_new0(virHostCPUTscInfo, 1); > VIR_AUTOCLOSE kvmFd = -1; > VIR_AUTOCLOSE vmFd = -1; > VIR_AUTOCLOSE vcpuFd = -1; > - uint64_t msr = 0; > int rc; > > if ((kvmFd = open(KVM_DEVICE, O_RDONLY)) < 0) { > @@ -1378,23 +1377,19 @@ virHostCPUGetTscInfo(void) > _("Unable to probe TSC frequency")); > return NULL; > } > - > - info = g_new0(virHostCPUTscInfo, 1); > - > info->frequency = rc * 1000ULL; > > - if (virHostCPUGetMSR(VMX_PROCBASED_CTLS2_MSR, &msr) == 0) { > - /* High 32 bits of the MSR value indicate whether specific control > - * can be set to 1. */ > - msr >>= 32; > - > - info->scaling = virTristateBoolFromBool(!!(msr & VMX_USE_TSC_SCALING)); > + if ((rc = ioctl(kvmFd, KVM_CHECK_EXTENSION, KVM_CAP_TSC_CONTROL)) < 0) { > + virReportSystemError(errno, "%s", > + _("Unable to query TSC scaling support")); > + return NULL; > } > + info->scaling = rc ? VIR_TRISTATE_BOOL_YES : VIR_TRISTATE_BOOL_NO; > > VIR_DEBUG("Detected TSC frequency %llu Hz, scaling %s", > info->frequency, virTristateBoolTypeToString(info->scaling)); > > - return info; > + return g_steal_pointer(&info); > } > > #else > I think you can also remove defines of those VMX_ macros that are being removed: # define VMX_PROCBASED_CTLS2_MSR 0x48b # define VMX_USE_TSC_SCALING (1 << 25) Reviewed-by: Michal Privoznik <mprivozn@xxxxxxxxxx> Michal
