Re: [PATCH v5 4/5] KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL

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

 




On Wed, 2018-01-31 at 13:53 -0800, Jim Mattson wrote:
> On Wed, Jan 31, 2018 at 1:42 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> 
> > Can we just say it sucks to be L2 too? :)  Because in the end as long as
> > no one ever writes to spec_ctrl, everybody is happy.
> 
> Unfortunately, quite a few OS vendors shipped IBRS-based mitigations
> earlier this month. (Has Redhat stopped writing to IA32_SPEC_CTRL yet?
> :-)
> 
> And in the long run, everyone is going to set IA32_SPEC_CTRL.IBRS=1 on
> CPUs with IA32_ARCH_CAPABILITIES.IBRS_ALL.


I'm actually working on IBRS_ALL at the moment.

I was tempted to *not* let the guests turn it off. Expose SPEC_CTRL but
just make it a no-op.

Or if that really doesn't fly, perhaps with IBRS_ALL we should invert
the logic. Set IBRS to 1 on vCPU reset, and only if it's set to *zero*
do we pass through the MSR and set the save_spec_ctrl_on_exit flag.

But let's get the code for *current* hardware done first...

Attachment: smime.p7s
Description: S/MIME cryptographic signature


[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