On Wed, Oct 30, 2019 at 02:28:02PM +0800, Luwei Kang wrote: > The CPUID level need to be set to 0x14 manually on old > machine-type if Intel PT is enabled in guest. e.g. in Qemu 3.1 > -machine pc-i440fx-3.1 -cpu qemu64,+intel-pt > will be CPUID[0].EAX(level)=7 and CPUID[7].EBX[25](intel-pt)=1. > > Some Intel PT capabilities are exposed by leaf 0x14 and the > missing capabilities will cause some MSRs access failed. > This patch add a warning message to inform the user to extend > the CPUID level.
Note that a warning is not an acceptable fix for a QEMU crash. We still need to fix the QEMU crash reported at: https://lore.kernel.org/qemu-devel/20191024141536.gu6...@habkost.net/ > > Suggested-by: Eduardo Habkost <ehabk...@redhat.com> > Signed-off-by: Luwei Kang <luwei.k...@intel.com> The subject line says "v1", but this patch is different from the v1 you sent earlier. If you are sending a different patch, please indicate it is a new version. Please also indicate what changed between different patch versions, to help review. > --- > target/i386/cpu.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/target/i386/cpu.c b/target/i386/cpu.c > index a624163..f67c479 100644 > --- a/target/i386/cpu.c > +++ b/target/i386/cpu.c > @@ -5440,8 +5440,12 @@ static void x86_cpu_expand_features(X86CPU *cpu, Error > **errp) > > /* Intel Processor Trace requires CPUID[0x14] */ > if ((env->features[FEAT_7_0_EBX] & CPUID_7_0_EBX_INTEL_PT) && > - kvm_enabled() && cpu->intel_pt_auto_level) { Not directly related to the warning: do you know why we have a kvm_enabled() check here? It seems unnecessary. We want CPUID level to be correct for all accelerators. > - x86_cpu_adjust_level(cpu, &cpu->env.cpuid_min_level, 0x14); > + kvm_enabled()) { > + if (cpu->intel_pt_auto_level) > + x86_cpu_adjust_level(cpu, &cpu->env.cpuid_min_level, 0x14); > + else > + warn_report("Intel PT need CPUID leaf 0x14, please set " > + "by \"-cpu ...,+intel-pt,level=0x14\""); The warning shouldn't be triggered if level is already >= 0x14. It is probably a good idea to mention that this happens only on pc-*-3.1 and older, as updating the machine-type is a better solution to the problem than manually setting the "level" property. This will print the warning multiple times if there are multiple VCPUs. You can use warn_report_once() to avoid that. > } > > /* CPU topology with multi-dies support requires CPUID[0x1F] */ > -- > 1.8.3.1 > -- Eduardo
