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

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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




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