Re: [PATCH v4 6/6] KVM: VMX: Make CR0.WP a guest owned bit

[Xiaoyao Li]

On 3/27/2023 4:37 PM, Mathias Krause wrote:
> On 27.03.23 10:33, Xiaoyao Li wrote:
> > On 3/22/2023 9:37 AM, Mathias Krause wrote:
> > > Guests like grsecurity that make heavy use of CR0.WP to implement kernel
> > > level W^X will suffer from the implied VMEXITs.
> > >
> > > With EPT there is no need to intercept a guest change of CR0.WP, so
> > > simply make it a guest owned bit if we can do so.
> >
> > I'm interested in the performance gain. Do you have data like Patch 2?
>
> It's mentioned in the cover letter[1], quoted below:

Sorry I missed it. The data of not intercepting CR0.WP looks great as well.

> [1]
> https://lore.kernel.org/kvm/20230322013731.102955-1-minipli@xxxxxxxxxxxxxx/
>
> : I used 'ssdd 10 50000' from rt-tests[5] as a micro-benchmark, running on a
> : grsecurity L1 VM. Below table shows the results (runtime in seconds, lower
> : is better):
> :
> :                               legacy     TDP    shadow
> :     kvm-x86/next@d8708b        8.43s    9.45s    70.3s
> :     + patches 1-3              5.39s    5.63s    70.2s
> :     + patches 4-6              3.51s    3.47s    67.8s
>
>
> Thanks,
> Mathias