linux-kernel - Re: [PATCH 2/2] KVM: MMU: allow more page become unsync at getting sp time

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Message-ID: <4BF9378B.4080703@redhat.com>
Date:	Sun, 23 May 2010 17:11:23 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
CC:	Marcelo Tosatti <mtosatti@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	KVM list <kvm@...r.kernel.org>
Subject: Re: [PATCH 2/2] KVM: MMU: allow more page become unsync at getting
 sp time

On 05/23/2010 03:16 PM, Xiao Guangrong wrote:
> Allow more page become asynchronous at getting sp time, if need create new
> shadow page for gfn but it not allow unsync(level>  1), we should unsync all
> gfn's unsync page
>
>
>
> +/* @gfn should be write-protected at the call site */
> +static void kvm_sync_pages(struct kvm_vcpu *vcpu,  gfn_t gfn)
> +{
> +	struct hlist_head *bucket;
> +	struct kvm_mmu_page *s;
> +	struct hlist_node *node, *n;
> +	unsigned index;
> +	bool flush = false;
> +
> +	index = kvm_page_table_hashfn(gfn);
> +	bucket =&vcpu->kvm->arch.mmu_page_hash[index];
> +	hlist_for_each_entry_safe(s, node, n, bucket, hash_link) {
>    

role.direct, role.invalid?

Well, role.direct cannot be unsync.  But that's not something we want to 
rely on.

This patch looks good too.

Some completely unrelated ideas:

- replace mmu_zap_page() calls in __kvm_sync_page() by setting 
role.invalid instead.  This reduces problems with the hash list being 
modified while we manipulate it.
- add a for_each_shadow_page_direct() { ... } and 
for_each_shadow_page_indirect() { ... } to replace the 
hlist_for_each_entry_safe()s.
- add kvm_tlb_gather() to reduce IPIs from kvm_mmu_zap_page()
- clear spte.accessed on speculative sptes (for example from invlpg) so 
the swapper won't keep them in ram unnecessarily

Again, completely unrelated to this patch set, just wrong them down so I 
don't forget them and to get your opinion.

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

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