Re: [PATCH v2] KVM: VMX: Cache IA32_DEBUGCTL in memory

[Radim KrÄmÃÅ]

2017-11-29 01:31-0800, Wanpeng Li:
> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> 
> MSR_IA32_DEBUGCTLMSR is zeroed on VMEXIT, so it is saved/restored 
> each time during world switch. Jim from Google pointed out that 
> when running schbench in L2, vmx_vcpu_run will occupy 4% cpu time, 
> and the 25% of vmx_vcpu_run cpu time is occupied by get_debugctlmsr(). 
> This patch caches the host IA32_DEBUGCTL MSR and saves/restores 
> the host IA32_DEBUGCTL msr when guest/host switches to avoid to 
> save/restore each time during world switch.
> 
> Suggested-by: Jim Mattson <jmattson@xxxxxxxxxx>
> Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> Cc: Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx>
> Cc: Jim Mattson <jmattson@xxxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> ---

Queued, thanks.

And there is another optimization loosely connected to the "[PATCH v3
00/16] Move vcpu_load and vcpu_put calls to arch code" series:
We only need to read the value for the KVM_RUN ioctl.