Re: [PATCH v2 5/7] KVM:VMX: Pass through host CET related MSRs to Guest.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Mon, Jan 28, 2019 at 05:20:24PM +0800, Yang Weijiang wrote:
> On Mon, Jan 28, 2019 at 07:28:42AM -0800, Sean Christopherson wrote:
> > On Sun, Jan 27, 2019 at 09:05:59PM +0800, Yang Weijiang wrote:
> > > On Fri, Jan 25, 2019 at 02:50:12PM -0800, Sean Christopherson wrote:
> > > > On Wed, Jan 23, 2019 at 04:59:07AM +0800, Yang Weijiang wrote:
> > > > > +
> > > > > +	msr_bitmap = vmx->vmcs01.msr_bitmap;
> > > > > +	best = kvm_find_cpuid_entry(vcpu, 7, 0);
> > > > > +	if ((best && best->function == 0x7) &&
> > > > > +	    ((best->ecx & bit(X86_FEATURE_SHSTK)) |
> > > > > +	    (best->edx & bit(X86_FEATURE_IBT)))) {
> > > > > +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_U_CET, MSR_TYPE_RW);
> > > > > +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_S_CET, MSR_TYPE_RW);
> > > > > +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_INT_SSP_TAB, MSR_TYPE_RW);
> > > > > +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PL0_SSP, MSR_TYPE_RW);
> > > > > +		vmx_disable_intercept_for_msr(msr_bitmap, MSR_IA32_PL3_SSP, MSR_TYPE_RW);
> > > > 
> > > > kvm_cpuid_update() an be called multiple times, don't we need to look
> > > > for a change in status as opposed to the bits being enabled?  And at
> > > > that point toggling interception should probably be wrapped in a helper
> > > > function.
> > > > 
> > >  Hi, Sean,
> > > 
> > >  Do you mean vmx_cpuid_update() here? I checked the code, it's called in
> > >  kvm_vcpu_ioctl_set_cpuid() and kvm_vcpu_ioctl_set_cpuid2(). Given that,
> > >  do I still need to check the bits before enable them?
> > 
> > Userspace can call the ioctl() any number of times, i.e. you can't
> > anything about the state of vmx->vmcs01.msr_bitmap.
> 
> OK, I'll add a flag in vcpu_vmx to mark the bit status and wrap the code in a
> helper.

A flag isn't necessary, just enable/disable the MSRs based on the new
CPUID value.  Updating the guest's CPUID values is relatively rare, i.e.
worst case scenario fiddling with the MSR bitmaps is redundant.



[Index of Archives]     [KVM ARM]     [KVM ia64]     [KVM ppc]     [Virtualization Tools]     [Spice Development]     [Libvirt]     [Libvirt Users]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite Questions]     [Linux Kernel]     [Linux SCSI]     [XFree86]

  Powered by Linux