Re: guest state leak into host

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Dong, Eddie wrote:
> Avi:
> 	Following commit mentioned guest state leaking into host, Can u
> explain a bit?
> 	In my understanding,  as if control goes to vmx_vcpu_run, CPU
> preemption is disabled, i.e. no rescheduling will happen (Guest
> resheduling will only happen at IOCTL return to Qemu time or vcpu_put at
> kvm_vcpu_ioctl_run). In this case, let machine FPU hold guest state
> (Linux Kernel itself will not use FPU), and machine MSRs (SYSCALL_MASK,
> LSTAR, K6_STAR, CSTAR, GS_BASE) hold for guest MSRs can avoid
> save/restore and thus performance gain. But I might make some mistake.
>   

Some exit handlers (even the #PF handler) can sleep sometimes.  They 
call kvm_arch_ops->vcpu_put(), do some sleepy thing, then call 
kvm_arch_ops->vcpu_load().  The changes in the commit make sure that if 
vcpu_put() is called, the lightweight exit is converted to a heavyweight 
exit.  Since such sleeps are rare, this is not expected to impact 
performance.

See for example mmu_topup_memory_caches().


-- 
error compiling committee.c: too many arguments to function


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