linux-kernel - Re: [PATCH 5/5] KVM: x86: MMU: Consolidate WARN_ON/BUG

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Date:	Tue, 10 Nov 2015 18:05:20 +0900
From:	Takuya Yoshikawa <yoshikawa_takuya_b1@....ntt.co.jp>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] KVM: x86: MMU: Consolidate WARN_ON/BUG_ON checks for
 reverse-mapped sptes

On 2015/11/09 19:14, Paolo Bonzini wrote:
> Can you also change kvm_mmu_mark_parents_unsync to use
> for_each_rmap_spte instead of pte_list_walk?  It is the last use of
> pte_list_walk, and it's nice if we have two uses of for_each_rmap_spte
> with parent_ptes as the argument.

No problem, I will do.

Since parent_ptes is also explained as the "reverse mapping" list of
parent sptes (in mmu.txt and kvm_host.h), using rmap helpers will not
look so strange.

> BTW, on my todo list is to change the rmap items to a struct (with a
> single u64 inside) for type safety.  Since you are touching this code,
> perhaps you can give it a shot?

Yes, almost done here (assuming that you mean 'unsigned long').
But I have some candidates for its name in mind:

1. struct kvm_rmap { unsigned long val; };
2. struct kvm_rmap_head { unsigned long val; };
3. struct kvm_rmap_list_head { unsigned long val; };
4. struct kvm_spte_list_head { unsigned long val; };

Since this is the head of the reverse mapping list of sptes, I thought
name 3 might be the best and first made a patch with it, but it was
a bit longer than I had hoped it to be.

I have changed it to name 2, and it looks a bit nicer now, but even
shorter, e.g. name 1, may be good as well.

Do you have any preference?

   Takuya

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