linux-kernel - Re: [PATCH v3 14/19] KVM: MMU: clean up spte updating and clearing

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Date:	Wed, 6 Jul 2011 14:39:11 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Xiao Guangrong <xiaoguangrong@...fujitsu.com>
Cc:	Avi Kivity <avi@...hat.com>, LKML <linux-kernel@...r.kernel.org>,
	KVM <kvm@...r.kernel.org>
Subject: Re: [PATCH v3 14/19] KVM: MMU: clean up spte updating and clearing

On Thu, Jun 30, 2011 at 04:25:34PM +0800, Xiao Guangrong wrote:
> Clean up the code between mmu_spte_clear_* and mmu_spte_update
> 
> Signed-off-by: Xiao Guangrong <xiaoguangrong@...fujitsu.com>
> ---
>  arch/x86/kvm/mmu.c |   75 +++++++++++++++++++++++++++-------------------------
>  1 files changed, 39 insertions(+), 36 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 48c0a45..857d0d6 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -279,24 +279,51 @@ static u64 __xchg_spte(u64 *sptep, u64 new_spte)
>  #endif
>  }
>  
> -static bool spte_has_volatile_bits(u64 spte)
> +static bool spte_is_bit_cleared(u64 old_spte, u64 new_spte, u64 bit_mask)
> +{
> +	return (old_spte & bit_mask) && !(new_spte & bit_mask);
> +}
> +
> +static bool spte_has_volatile_bits(u64 spte, u64 keep_bits)
>  {
> +	bool access_nonvolatile = false, dirty_nonvolatile = false;
> +
>  	if (!shadow_accessed_mask)
>  		return false;
>  
> -	if (!is_shadow_present_pte(spte))
> -		return false;
> +	if ((spte | keep_bits) & shadow_accessed_mask)
> +		access_nonvolatile = true;
> +
> +	if (!is_writable_pte(spte) || ((spte | keep_bits) & shadow_dirty_mask))
> +		dirty_nonvolatile = true;
>  
> -	if ((spte & shadow_accessed_mask) &&
> -	      (!is_writable_pte(spte) || (spte & shadow_dirty_mask)))
> +	if (access_nonvolatile && dirty_nonvolatile)
>  		return false;
>  
>  	return true;
>  }
>  
> -static bool spte_is_bit_cleared(u64 old_spte, u64 new_spte, u64 bit_mask)
> +static void track_spte_bits(u64 old_spte, u64 keep_bits, bool always_track)
>  {
> -	return (old_spte & bit_mask) && !(new_spte & bit_mask);
> +	if (always_track ||
> +	      (spte_is_bit_cleared(old_spte, keep_bits, shadow_accessed_mask)))
> +		kvm_set_pfn_accessed(spte_to_pfn(old_spte));
> +
> +	if (always_track ||
> +	      (spte_is_bit_cleared(old_spte, keep_bits, shadow_dirty_mask)))
> +		kvm_set_pfn_dirty(spte_to_pfn(old_spte));
> +}

This is much more confusing than previously, please drop it.

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