Re: [RFC][PATCH v2 00/21] x86/pti: Defer CR3 switch to C code

Borislav Petkov
2020-11-17T18:28:48Z

On Tue, Nov 17, 2020 at 07:12:07PM +0100, Alexandre Chartre wrote:
> Yes. L1TF/MDS allow some inter cpu-thread attacks which are not mitigated at
> the moment. In particular, this allows a guest VM to attack another guest VM
> or the host kernel running on a sibling cpu-thread. Core Scheduling will
> mitigate the guest-to-guest attack but not the guest-to-host attack.

I see in vmx_vcpu_enter_exit():

/* L1D Flush includes CPU buffer clear to mitigate MDS */
if (static_branch_unlikely(&vmx_l1d_should_flush))
vmx_l1d_flush(vcpu);
else if (static_branch_unlikely(&mds_user_clear))
mds_clear_cpu_buffers();

Is that not enough?

--
Regards/Gruss,
Boris.