[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH RESEND v1 2/7] x86: configure vmcs for Intel processor trace virtualization
> >>> On 28.04.18 at 03:07, <luwei.kang@xxxxxxxxx> wrote: > >> > @@ -383,13 +388,28 @@ static int vmx_init_vmcs_config(void) > >> > _vmx_secondary_exec_control &= > >> > ~SECONDARY_EXEC_ENABLE_VIRT_EXCEPTIONS; > >> > > >> > min = 0; > >> > - opt = VM_ENTRY_LOAD_GUEST_PAT | VM_ENTRY_LOAD_BNDCFGS; > >> > + opt = VM_ENTRY_LOAD_GUEST_PAT | VM_ENTRY_LOAD_BNDCFGS | > >> > + VM_ENTRY_CONCEAL_PT_PIP | VM_ENTRY_LOAD_IA32_RTIT_CTL; > >> > _vmx_vmentry_control = adjust_vmx_controls( > >> > "VMEntry Control", min, opt, MSR_IA32_VMX_ENTRY_CTLS, > >> > &mismatch); > >> > > >> > if ( mismatch ) > >> > return -EINVAL; > >> > > >> > + if ( !(_vmx_secondary_exec_control & > >> > + SECONDARY_EXEC_ENABLE_EPT) > >> || > >> > + !(_vmx_secondary_exec_control & > >> > + SECONDARY_EXEC_PT_USE_GPA) > >> || > >> > + !(_vmx_vmexit_control & VM_EXIT_CLEAR_IA32_RTIT_CTL) || > >> > + !(_vmx_vmentry_control & VM_ENTRY_LOAD_IA32_RTIT_CTL) ) > >> > + { > >> > + _vmx_secondary_exec_control &= > >> ~(SECONDARY_EXEC_PT_USE_GPA | > >> > + SECONDARY_EXEC_CONCEAL_PT_PIP); > >> > + _vmx_vmexit_control &= ~(VM_EXIT_CONCEAL_PT_PIP | > >> > + VM_EXIT_CLEAR_IA32_RTIT_CTL); > >> > + _vmx_vmentry_control &= ~(VM_ENTRY_CONCEAL_PT_PIP | > >> > + VM_ENTRY_LOAD_IA32_RTIT_CTL); > >> > + opt_intel_pt = 0; > >> > + } > >> > >> Besides clearing the flag here, shouldn't you also check it further up? > > > > If " opt_intel_pt =0" represent user don't want to use this feature to > > all guest or hardware don't support it at all. If flag "opt_intel_pt " > > still true after this check represent the user want to use this > > feature and hardware have capability to support PT in guest. This is > > depend on hardware capability and the parameter set of xen command line > > "ipt=1". > > I'm having some difficulty to follow this, so let me explain my point a little > further: If (part of) the required features is available in hardware, but the > user opted to not use IPT, wouldn't it be better for > consistency to turn off the individual IPT features (so that e.g. checks of > them elsewhere in the code won't go wrong), i.e. pretend > the hardware doesn't support them? If the hardware have the capability to enable IPT in guest but the user don't want to use it. We can set "intel_pt = 0" in XEN command line to disable this feature so that IPT will can't be detected in all guest. Thanks, Luwei Kang > > Jan > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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