Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933935AbaFRFtP (ORCPT ); Wed, 18 Jun 2014 01:49:15 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:48018 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1756610AbaFRFtN (ORCPT ); Wed, 18 Jun 2014 01:49:13 -0400 X-IronPort-AV: E=Sophos;i="5.00,730,1396972800"; d="scan'208";a="32071738" From: Tang Chen To: , , , , , , CC: , , , , , , Subject: [RFC PATCH 1/1] Move two pinned pages to non-movable node in kvm. Date: Wed, 18 Jun 2014 13:50:00 +0800 Message-ID: <1403070600-6083-1-git-send-email-tangchen@cn.fujitsu.com> X-Mailer: git-send-email 1.7.11.7 MIME-Version: 1.0 Content-Type: text/plain 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, I met a problem when offlining memory with a kvm guest running. [Problem] When qemu creates vpus, it will call the following two functions to allocate two pages: 1. alloc_apic_access_page(): allocate apic access page for FlexPriority in intel cpu. 2. alloc_identity_pagetable(): allocate ept identity pagetable for real mode. And unfortunately, these two pages will be pinned in memory, and they cannot be migrated. As a result, they cannot be offlined. And memory hot-remove will fail. [The way I tried] I tried to migrate these two pages, but I think I cannot find a proper way to migrate them. Let's take ept identity pagetable for example: In my opinion, since it is pagetable, CPU will access this page every time the guest read/write memory. For example, the following code will access memory: int a; a = 0; So this ept identity pagetable page can be accessed at any time by CPU automatically. [Solution] I have a basic idea to solve this problem: allocate these two pages in non-movable nodes. (For now, we can only hot-remove memory in movable nodes.) alloc_identity_pagetable() |-> __kvm_set_memory_region() | |-> kvm_arch_prepare_memory_region() | |-> userspace_addr = vm_mmap(); | |-> memslot->userspace_addr = userspace_addr; /* map usespace address (qemu) */ | | /* | * Here, set memory policy for the mapped but not allocated page, | * make it can only be allocated in non-movable nodes. | * (We can reuse "numa_kernel_nodes" node mask in movable_node functionality.) | */ | |-> page = gfn_to_page() /* allocate and pin page */ Please refer to the attached patch for detail. I did some basic test for the patch, and it will make memory offline succeed. [Questions] And by the way, would you guys please answer the following questions for me ? 1. What's the ept identity pagetable for ? Only one page is enough ? 2. Is the ept identity pagetable only used in realmode ? Can we free it once the guest is up (vcpu in protect mode)? 3. Now, ept identity pagetable is allocated in qemu userspace. Can we allocate it in kernel space ? 4. If I want to migrate these two pages, what do you think is the best way ? Thanks. Signed-off-by: Tang Chen --- arch/x86/include/asm/numa.h | 1 + arch/x86/kvm/vmx.c | 5 +++++ arch/x86/kvm/x86.c | 1 + arch/x86/mm/numa.c | 3 ++- include/linux/mempolicy.h | 6 ++++++ mm/mempolicy.c | 9 +++++++++ 6 files changed, 24 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/numa.h b/arch/x86/include/asm/numa.h index 4064aca..6312577 100644 --- a/arch/x86/include/asm/numa.h +++ b/arch/x86/include/asm/numa.h @@ -30,6 +30,7 @@ extern int numa_off; */ extern s16 __apicid_to_node[MAX_LOCAL_APIC]; extern nodemask_t numa_nodes_parsed __initdata; +extern nodemask_t numa_kernel_nodes; extern int __init numa_add_memblk(int nodeid, u64 start, u64 end); extern void __init numa_set_distance(int from, int to, int distance); diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index 801332e..4a3b5b5 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -32,6 +32,7 @@ #include #include #include +#include #include "kvm_cache_regs.h" #include "x86.h" @@ -3988,6 +3989,8 @@ static int alloc_apic_access_page(struct kvm *kvm) if (r) goto out; + numa_bind_non_movable(kvm_userspace_mem.userspace_addr, PAGE_SIZE); + page = gfn_to_page(kvm, 0xfee00); if (is_error_page(page)) { r = -EFAULT; @@ -4018,6 +4021,8 @@ static int alloc_identity_pagetable(struct kvm *kvm) if (r) goto out; + numa_bind_non_movable(kvm_userspace_mem.userspace_addr, PAGE_SIZE); + page = gfn_to_page(kvm, kvm->arch.ept_identity_map_addr >> PAGE_SHIFT); if (is_error_page(page)) { r = -EFAULT; diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index f32a025..3962a23 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -7295,6 +7295,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm, return PTR_ERR((void *)userspace_addr); memslot->userspace_addr = userspace_addr; + mem->userspace_addr = userspace_addr; } return 0; diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c index a32b706..d706148 100644 --- a/arch/x86/mm/numa.c +++ b/arch/x86/mm/numa.c @@ -22,6 +22,8 @@ int __initdata numa_off; nodemask_t numa_nodes_parsed __initdata; +nodemask_t numa_kernel_nodes; +EXPORT_SYMBOL(numa_kernel_nodes); struct pglist_data *node_data[MAX_NUMNODES] __read_mostly; EXPORT_SYMBOL(node_data); @@ -557,7 +559,6 @@ static void __init numa_init_array(void) static void __init numa_clear_kernel_node_hotplug(void) { int i, nid; - nodemask_t numa_kernel_nodes = NODE_MASK_NONE; unsigned long start, end; struct memblock_region *r; diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h index f230a97..14f3f04 100644 --- a/include/linux/mempolicy.h +++ b/include/linux/mempolicy.h @@ -140,6 +140,7 @@ bool vma_policy_mof(struct task_struct *task, struct vm_area_struct *vma); extern void numa_default_policy(void); extern void numa_policy_init(void); +extern long numa_bind_non_movable(unsigned long start, unsigned long len); extern void mpol_rebind_task(struct task_struct *tsk, const nodemask_t *new, enum mpol_rebind_step step); extern void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new); @@ -243,6 +244,11 @@ static inline void numa_default_policy(void) { } +static inline long numa_bind_non_movable(unsigned long start, unsigned long len) +{ + return -EINVAL; +} + static inline void mpol_rebind_task(struct task_struct *tsk, const nodemask_t *new, enum mpol_rebind_step step) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 2849742..20065a9 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -97,6 +97,7 @@ #include #include +#include #include #include "internal.h" @@ -2663,6 +2664,14 @@ void numa_default_policy(void) do_set_mempolicy(MPOL_DEFAULT, 0, NULL); } +/* Bind a memory range to non-movable nodes. */ +long numa_bind_non_movable(unsigned long start, unsigned long len) +{ + return do_mbind(start, len, MPOL_BIND, MPOL_MODE_FLAGS, + &numa_kernel_nodes, MPOL_MF_STRICT); +} +EXPORT_SYMBOL(numa_bind_non_movable); + /* * Parse and format mempolicy from/to strings */ -- 1.8.3.1 -- 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/