Re: [patch 2/3] KVM: MMU: skip global pgtables on sync due to cr3 switch

[Avi Kivity <avi@redhat.com>]

Marcelo Tosatti wrote:
> Skip syncing global pages on cr3 switch (but not on cr4/cr0). This is
> important for Linux 32-bit guests with PAE, where the kmap page is
> marked as global.
>
>   

Patch is good, but won't apply without the first.

>  {
>  	u64 spte;
>  	int ret = 0;
>  	u64 mt_mask = shadow_mt_mask;
> +	struct kvm_mmu_page *sp = page_header(__pa(shadow_pte));
> +
> +	if (!global && sp->global) {
> +		sp->global = 0;
>   

A slight deficiency in this approach is that a page can't transition 
from !global to global.  I don't think this is frequent, so we don't 
need to deal with it.  But a more accurate approach is to keep a count 
of non-global present mappings, and to activate the global logic when 
this count is nonzero.



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