linux-kernel - RE: [PATCH v3 4/4] Enabling Access bit when doing memory swapping

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Date:	Wed, 23 May 2012 13:31:23 +0000
From:	"Hao, Xudong" <xudong.hao@...el.com>
To:	"avi@...hat.com" <avi@...hat.com>
CC:	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mtosatti@...hat.com" <mtosatti@...hat.com>,
	"takuya.yoshikawa@...il.com" <takuya.yoshikawa@...il.com>,
	"Zhang, Xiantao" <xiantao.zhang@...el.com>,
	"Shan, Haitao" <haitao.shan@...el.com>
Subject: RE: [PATCH v3 4/4] Enabling Access bit when doing memory swapping

Hi, Avi

Will these patches be accepted if no other comments?

Thanks,
-Xudong


> -----Original Message-----
> From: Hao, Xudong
> Sent: Tuesday, May 22, 2012 11:23 AM
> To: avi@...hat.com
> Cc: kvm@...r.kernel.org; linux-kernel@...r.kernel.org; mtosatti@...hat.com;
> takuya.yoshikawa@...il.com; Zhang, Xiantao; Hao, Xudong; Shan, Haitao
> Subject: [PATCH v3 4/4] Enabling Access bit when doing memory swapping
> 
> <Re-send>
> 
> Enabling Access bit when doing memory swapping.
> 
> Changes from v2:
> -Still using claer_bit() function to make sure it's atomic operation.
> 
> Signed-off-by: Haitao Shan <haitao.shan@...el.com>
> Signed-off-by: Xudong Hao <xudong.hao@...el.com>
> ---
>  arch/x86/kvm/mmu.c |   14 ++++++++------
>  arch/x86/kvm/vmx.c |    6 ++++--
>  2 files changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index 72102e0..c2fef8e 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -1242,7 +1242,8 @@ static int kvm_age_rmapp(struct kvm *kvm,
> unsigned long *rmapp,
>  	int young = 0;
> 
>  	/*
> -	 * Emulate the accessed bit for EPT, by checking if this page has
> +	 * In case of absence of EPT Access and Dirty Bits supports,
> +	 * emulate the accessed bit for EPT, by checking if this page has
>  	 * an EPT mapping, and clearing it if it does. On the next access,
>  	 * a new EPT mapping will be established.
>  	 * This has some overhead, but not as much as the cost of swapping
> @@ -1253,11 +1254,12 @@ static int kvm_age_rmapp(struct kvm *kvm,
> unsigned long *rmapp,
> 
>  	for (sptep = rmap_get_first(*rmapp, &iter); sptep;
>  	     sptep = rmap_get_next(&iter)) {
> -		BUG_ON(!(*sptep & PT_PRESENT_MASK));
> +		BUG_ON(!is_shadow_present_pte(*sptep));
> 
> -		if (*sptep & PT_ACCESSED_MASK) {
> +		if (*sptep & shadow_accessed_mask) {
>  			young = 1;
> -			clear_bit(PT_ACCESSED_SHIFT, (unsigned long *)sptep);
> +			clear_bit((ffs(shadow_accessed_mask) - 1),
> +				 (unsigned long *)sptep);
>  		}
>  	}
> 
> @@ -1281,9 +1283,9 @@ static int kvm_test_age_rmapp(struct kvm *kvm,
> unsigned long *rmapp,
> 
>  	for (sptep = rmap_get_first(*rmapp, &iter); sptep;
>  	     sptep = rmap_get_next(&iter)) {
> -		BUG_ON(!(*sptep & PT_PRESENT_MASK));
> +		BUG_ON(!is_shadow_present_pte(*sptep));
> 
> -		if (*sptep & PT_ACCESSED_MASK) {
> +		if (*sptep & shadow_accessed_mask) {
>  			young = 1;
>  			break;
>  		}
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 32eb588..ea6390e 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -7275,8 +7275,10 @@ static int __init vmx_init(void)
>  	vmx_disable_intercept_for_msr(MSR_IA32_SYSENTER_EIP, false);
> 
>  	if (enable_ept) {
> -		kvm_mmu_set_mask_ptes(0ull, 0ull, 0ull, 0ull,
> -				VMX_EPT_EXECUTABLE_MASK);
> +		kvm_mmu_set_mask_ptes(0ull,
> +			(enable_ept_ad_bits) ? VMX_EPT_ACCESS_BIT : 0ull,
> +			(enable_ept_ad_bits) ? VMX_EPT_DIRTY_BIT : 0ull,
> +			0ull, VMX_EPT_EXECUTABLE_MASK);
>  		ept_set_mmio_spte_mask();
>  		kvm_enable_tdp();
>  	} else
> --
> 1.5.6

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