Re: merge kvm_flush_remote_tlbs when modifing shadow pte

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

Dong, Eddie wrote:
> host side TLB flush can be merged together if multiple
> spte need to be write-protected.
>
> Signed-off-by: Yaozu (Eddie) Dong <eddie.dong-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
>
> diff --git a/drivers/kvm/mmu.c b/drivers/kvm/mmu.c
> index 92ac0d1..749db46 100644
> --- a/drivers/kvm/mmu.c
> +++ b/drivers/kvm/mmu.c
> @@ -524,9 +524,9 @@ static void rmap_write_protect(struct kvm *kvm, u64
> gfn)
>  		rmap_printk("rmap_write_protect: spte %p %llx\n", spte,
> *spte);
>  		if (is_writeble_pte(*spte))
>  			set_shadow_pte(spte, *spte & ~PT_WRITABLE_MASK);
> -		kvm_flush_remote_tlbs(kvm);
>  		spte = rmap_next(kvm, rmapp, spte);
>  	}
> +	kvm_flush_remote_tlbs(kvm);
>  }
>   


I think this can be improved; in case we don't touch the shadow pte at 
all, there is no need to flush the tlbs.

Also, please pull from kvm.git; things have moved around (mmu.c is now 
in arch/x86/kvm/).


-- 
Any sufficiently difficult bug is indistinguishable from a feature.


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