On Sat, 6 Jan 2018, tip-bot for Tom Lendacky wrote:
> Commit-ID: 0bf17c102177d5da9363bf8b1e4704b9996d5079
> Gitweb:
> https://git.kernel.org/tip/0bf17c102177d5da9363bf8b1e4704b9996d5079
> Author: Tom Lendacky <thomas.lenda...@amd.com>
> AuthorDate: Fri, 5 Jan 2018 10:07:56 -0600
> Committer: Thomas Gleixner <t...@linutronix.de>
> CommitDate: Sat, 6 Jan 2018 21:57:40 +0100
>
> x86/cpu/AMD: Use LFENCE_RDTSC instead of MFENCE_RDTSC
>
> With LFENCE now a serializing instruction, set the LFENCE_RDTSC
> feature since the LFENCE instruction has less overhead than the
> MFENCE instruction.
Second thoughts on that. As pointed out by someone in one of the insane
long threads:
What happens if the kernel runs as a guest and
- the hypervisor did not set the LFENCE to serializing on the host
- the hypervisor does not allow writing MSR_AMD64_DE_CFG
That would bring the guest into a pretty bad state or am I missing
something essential here?
I'm dropping these patches until this question is answered.
Thanks,
tglx
