Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753975AbaGNJQM (ORCPT ); Mon, 14 Jul 2014 05:16:12 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:37847 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1753438AbaGNJQH (ORCPT ); Mon, 14 Jul 2014 05:16:07 -0400 X-IronPort-AV: E=Sophos;i="5.00,888,1396972800"; d="scan'208";a="33232887" Message-ID: <53C3A010.6000405@cn.fujitsu.com> Date: Mon, 14 Jul 2014 17:17:04 +0800 From: Tang Chen User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20120430 Thunderbird/12.0.1 MIME-Version: 1.0 To: Gleb Natapov CC: , , , , , , , Tang Chen Subject: Re: [RESEND PATCH v2 4/5] kvm: Remove ept_identity_pagetable from struct kvm_arch. References: <1404824492-30095-5-git-send-email-tangchen@cn.fujitsu.com> <1404871683-27293-1-git-send-email-tangchen@cn.fujitsu.com> <20140712074425.GG4399@minantech.com> In-Reply-To: <20140712074425.GG4399@minantech.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.167.226.99] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Gleb, Please see below. On 07/12/2014 03:44 PM, Gleb Natapov wrote: > On Wed, Jul 09, 2014 at 10:08:03AM +0800, Tang Chen wrote: >> kvm_arch->ept_identity_pagetable holds the ept identity pagetable page. But >> it is never used to refer to the page at all. >> >> In vcpu initialization, it indicates two things: >> 1. indicates if ept page is allocated >> 2. indicates if a memory slot for identity page is initialized >> >> Actually, kvm_arch->ept_identity_pagetable_done is enough to tell if the ept >> identity pagetable is initialized. So we can remove ept_identity_pagetable. >> >> Signed-off-by: Tang Chen >> --- >> arch/x86/include/asm/kvm_host.h | 1 - >> arch/x86/kvm/vmx.c | 25 +++++++++++-------------- >> 2 files changed, 11 insertions(+), 15 deletions(-) >> >> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h >> index 4931415..62f973e 100644 >> --- a/arch/x86/include/asm/kvm_host.h >> +++ b/arch/x86/include/asm/kvm_host.h >> @@ -578,7 +578,6 @@ struct kvm_arch { >> >> gpa_t wall_clock; >> >> - struct page *ept_identity_pagetable; >> bool ept_identity_pagetable_done; >> gpa_t ept_identity_map_addr; >> >> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >> index 0918635e..fe2e5f4 100644 >> --- a/arch/x86/kvm/vmx.c >> +++ b/arch/x86/kvm/vmx.c >> @@ -741,6 +741,7 @@ static void vmx_sync_pir_to_irr_dummy(struct kvm_vcpu *vcpu); >> static void copy_vmcs12_to_shadow(struct vcpu_vmx *vmx); >> static void copy_shadow_to_vmcs12(struct vcpu_vmx *vmx); >> static bool vmx_mpx_supported(void); >> +static int alloc_identity_pagetable(struct kvm *kvm); >> >> static DEFINE_PER_CPU(struct vmcs *, vmxarea); >> static DEFINE_PER_CPU(struct vmcs *, current_vmcs); >> @@ -3921,21 +3922,21 @@ out: >> >> static int init_rmode_identity_map(struct kvm *kvm) >> { >> - int i, idx, r, ret; >> + int i, idx, r, ret = 0; >> pfn_t identity_map_pfn; >> u32 tmp; >> >> if (!enable_ept) >> return 1; >> - if (unlikely(!kvm->arch.ept_identity_pagetable)) { >> - printk(KERN_ERR "EPT: identity-mapping pagetable " >> - "haven't been allocated!\n"); >> - return 0; >> - } >> if (likely(kvm->arch.ept_identity_pagetable_done)) >> return 1; >> - ret = 0; >> identity_map_pfn = kvm->arch.ept_identity_map_addr>> PAGE_SHIFT; >> + >> + mutex_lock(&kvm->slots_lock); > Why move this out of alloc_identity_pagetable()? > Referring to the original code, I think mutex_lock(&kvm->slots_lock) is used to protect kvm->arch.ept_identity_pagetable. If two or more threads try to modify it at the same time, the mutex ensures that the identity table is only allocated once. Now, we dropped kvm->arch.ept_identity_pagetable. And use kvm->arch.ept_identity_pagetable_done to check if the identity table is allocated and initialized. So we should protect memory slot operation in alloc_identity_pagetable() and kvm->arch.ept_identity_pagetable_done with this mutex. Of course, I can see that the name "slots_lock" indicates that it may be used to protect the memory slot operation only. Maybe move it out here is not suitable. If I'm wrong, please tell me. >> + r = alloc_identity_pagetable(kvm); >> + if (r) >> + goto out2; >> + >> idx = srcu_read_lock(&kvm->srcu); >> r = kvm_clear_guest_page(kvm, identity_map_pfn, 0, PAGE_SIZE); >> if (r< 0) >> @@ -3953,6 +3954,9 @@ static int init_rmode_identity_map(struct kvm *kvm) >> ret = 1; >> out: >> srcu_read_unlock(&kvm->srcu, idx); >> + >> +out2: >> + mutex_unlock(&kvm->slots_lock); >> return ret; >> } >> >> @@ -4006,9 +4010,6 @@ static int alloc_identity_pagetable(struct kvm *kvm) >> struct kvm_userspace_memory_region kvm_userspace_mem; >> int r = 0; >> >> - mutex_lock(&kvm->slots_lock); >> - if (kvm->arch.ept_identity_pagetable) >> - goto out; >> kvm_userspace_mem.slot = IDENTITY_PAGETABLE_PRIVATE_MEMSLOT; >> kvm_userspace_mem.flags = 0; >> kvm_userspace_mem.guest_phys_addr = >> @@ -4025,9 +4026,7 @@ static int alloc_identity_pagetable(struct kvm *kvm) >> goto out; >> } >> >> - kvm->arch.ept_identity_pagetable = page; > I think we can drop gfn_to_page() above too now. Why would we need it? > Yes, will remove it in the next version. Thanks. >> out: >> - mutex_unlock(&kvm->slots_lock); >> return r; >> } >> >> @@ -7583,8 +7582,6 @@ static struct kvm_vcpu *vmx_create_vcpu(struct kvm *kvm, unsigned int id) >> kvm->arch.ept_identity_map_addr = >> VMX_EPT_IDENTITY_PAGETABLE_ADDR; >> err = -ENOMEM; >> - if (alloc_identity_pagetable(kvm) != 0) >> - goto free_vmcs; >> if (!init_rmode_identity_map(kvm)) >> goto free_vmcs; >> } >> -- >> 1.8.3.1 >> > > -- > Gleb. > . > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/