Re: [PATCH v2 1/5] KVM: Add APIs for unlocked TLB flush

[Avi Kivity <avi@redhat.com>]

On 05/17/2012 01:24 PM, Avi Kivity wrote:
> Currently we flush the TLB while holding mmu_lock.  This
> increases the lock hold time by the IPI round-trip time, increasing
> contention, and makes dropping the lock (for latency reasons) harder.
>
> This patch changes TLB management to be usable locklessly, introducing
> the following APIs:
>
>   kvm_mark_tlb_dirty() - mark the TLB as containing stale entries
>   kvm_cond_flush_remote_tlbs() - flush the TLB if it was marked as
>                                   dirty
>
> These APIs can be used without holding mmu_lock (though if the TLB
> became stale due to shadow page table modifications, typically it
> will need to be called with the lock held to prevent other threads
> from seeing the modified page tables with the TLB unmarked and unflushed)/
>


Oops, forgot the cover letter and the changelog.  I'm experimenting with
posting directly from git send-email.

The change is the new patch 2 which tries to ensure we never bypass a
tlb flush.  Perhaps a better way to do it is to move the
kvm_cond_flush_remote_tlbs() _before_ the code that depends on them,
instead of after the code that changes the spte.

Please review carefully.

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