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From: Marcelo Tosatti <mtosatti@redhat.com>
To: kvm@vger.kernel.org
Cc: avi@redhat.com, Marcelo Tosatti <mtosatti@redhat.com>
Subject: [patch 07/10] KVM: introduce kvm->srcu and convert kvm_set_memory_region to SRCU update
Date: Mon, 21 Sep 2009 20:37:18 -0300
Message-ID: <20090921234124.596305294@amt.cnet> (raw)
In-Reply-To: <20090921233711.213665413@amt.cnet>


[-- Attachment #0: introduce-srcu-and-use-for-slots --]
[-- Type: text/plain, Size: 13379 bytes --]

Use two steps for memslot deletion: mark the slot invalid (which stops 
instantiation of new shadow pages for that slot, but allows destruction),
then instantiate the new empty slot.

Also simplifies kvm_handle_hva locking.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: kvm-slotslock/include/linux/kvm.h
===================================================================
--- kvm-slotslock.orig/include/linux/kvm.h
+++ kvm-slotslock/include/linux/kvm.h
@@ -39,7 +39,7 @@ struct kvm_userspace_memory_region {
 
 /* for kvm_memory_region::flags */
 #define KVM_MEM_LOG_DIRTY_PAGES  1UL
-
+#define KVM_MEMSLOT_INVALID      (1UL << 1)
 
 /* for KVM_IRQ_LINE */
 struct kvm_irq_level {
Index: kvm-slotslock/virt/kvm/kvm_main.c
===================================================================
--- kvm-slotslock.orig/virt/kvm/kvm_main.c
+++ kvm-slotslock/virt/kvm/kvm_main.c
@@ -43,6 +43,7 @@
 #include <linux/swap.h>
 #include <linux/bitops.h>
 #include <linux/spinlock.h>
+#include <linux/srcu.h>
 
 #include <asm/processor.h>
 #include <asm/io.h>
@@ -352,11 +353,15 @@ static struct kvm *kvm_create_vm(void)
 	kvm->memslots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
 	if (!kvm->memslots)
 		goto out_err;
+	if (init_srcu_struct(&kvm->srcu))
+		goto out_err;
 
 #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
 	page = alloc_page(GFP_KERNEL | __GFP_ZERO);
-	if (!page)
+	if (!page) {
+		cleanup_srcu_struct(&kvm->srcu);
 		goto out_err;
+	}
 
 	kvm->coalesced_mmio_ring =
 			(struct kvm_coalesced_mmio_ring *)page_address(page);
@@ -367,6 +372,7 @@ static struct kvm *kvm_create_vm(void)
 		kvm->mmu_notifier.ops = &kvm_mmu_notifier_ops;
 		r = mmu_notifier_register(&kvm->mmu_notifier, current->mm);
 		if (r) {
+			cleanup_srcu_struct(&kvm->srcu);
 #ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
 			put_page(page);
 #endif
@@ -462,6 +468,7 @@ static void kvm_destroy_vm(struct kvm *k
 	kvm_arch_flush_shadow(kvm);
 #endif
 	kvm_arch_destroy_vm(kvm);
+	cleanup_srcu_struct(&kvm->srcu);
 	hardware_disable_all();
 	mmdrop(mm);
 }
@@ -502,12 +509,13 @@ int __kvm_set_memory_region(struct kvm *
 			    struct kvm_userspace_memory_region *mem,
 			    int user_alloc)
 {
-	int r;
+	int r, flush_shadow = 0;
 	gfn_t base_gfn;
 	unsigned long npages;
 	unsigned long i;
 	struct kvm_memory_slot *memslot;
 	struct kvm_memory_slot old, new;
+	struct kvm_memslots *slots, *old_memslots;
 
 	r = -EINVAL;
 	/* General sanity checks */
@@ -569,15 +577,7 @@ int __kvm_set_memory_region(struct kvm *
 		memset(new.rmap, 0, npages * sizeof(*new.rmap));
 
 		new.user_alloc = user_alloc;
-		/*
-		 * hva_to_rmmap() serialzies with the mmu_lock and to be
-		 * safe it has to ignore memslots with !user_alloc &&
-		 * !userspace_addr.
-		 */
-		if (user_alloc)
-			new.userspace_addr = mem->userspace_addr;
-		else
-			new.userspace_addr = 0;
+		new.userspace_addr = mem->userspace_addr;
 	}
 	if (!npages)
 		goto skip_lpage;
@@ -632,8 +632,9 @@ skip_lpage:
 		if (!new.dirty_bitmap)
 			goto out_free;
 		memset(new.dirty_bitmap, 0, dirty_bytes);
+		/* destroy any largepage mappings for dirty tracking */
 		if (old.npages)
-			kvm_arch_flush_shadow(kvm);
+			flush_shadow = 1;
 	}
 #else  /* not defined CONFIG_S390 */
 	new.user_alloc = user_alloc;
@@ -641,34 +642,69 @@ skip_lpage:
 		new.userspace_addr = mem->userspace_addr;
 #endif /* not defined CONFIG_S390 */
 
-	if (!npages)
+	if (!npages) {
+		slots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
+		if (!slots)
+			goto out_free;
+		memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
+		if (mem->slot >= slots->nmemslots)
+			slots->nmemslots = mem->slot + 1;
+		slots->memslots[mem->slot].flags |= KVM_MEMSLOT_INVALID;
+
+		old_memslots = kvm->memslots;
+		rcu_assign_pointer(kvm->memslots, slots);
+		synchronize_srcu(&kvm->srcu);
+		/* From this point no new shadow pages pointing to a deleted
+		 * memslot will be created.
+         	 *
+         	 * validation of sp->gfn happens in:
+         	 * 	- gfn_to_hva (kvm_read_guest, gfn_to_pfn)
+         	 * 	- kvm_is_visible_gfn (mmu_check_roots)
+         	 */
 		kvm_arch_flush_shadow(kvm);
+		kfree(old_memslots);
+	}
 
 	r = kvm_arch_prepare_memory_region(kvm, &new, old, user_alloc);
 	if (r)
 		goto out_free;
 
-	spin_lock(&kvm->mmu_lock);
-	if (mem->slot >= kvm->memslots->nmemslots)
-		kvm->memslots->nmemslots = mem->slot + 1;
+#ifdef CONFIG_DMAR
+	/* map the pages in iommu page table */
+	if (npages)
+		r = kvm_iommu_map_pages(kvm, &new);
+		if (r)
+			goto out_free;
+#endif
 
-	*memslot = new;
-	spin_unlock(&kvm->mmu_lock);
+	slots = kzalloc(sizeof(struct kvm_memslots), GFP_KERNEL);
+	if (!slots)
+		goto out_free;
+	memcpy(slots, kvm->memslots, sizeof(struct kvm_memslots));
+	if (mem->slot >= slots->nmemslots)
+		slots->nmemslots = mem->slot + 1;
+
+	/* actual memory is freed via old in kvm_free_physmem_slot below */
+	if (!npages) {
+		new.rmap = NULL;
+		new.dirty_bitmap = NULL;
+		for (i = 0; i < KVM_NR_PAGE_SIZES - 1; ++i)
+			new.lpage_info[i] = NULL;
+	}
+
+	slots->memslots[mem->slot] = new;
+	old_memslots = kvm->memslots;
+	rcu_assign_pointer(kvm->memslots, slots);
+	synchronize_srcu(&kvm->srcu);
 
 	kvm_arch_commit_memory_region(kvm, mem, old, user_alloc);
 
-	kvm_free_physmem_slot(&old, npages ? &new : NULL);
-	/* Slot deletion case: we have to update the current slot */
-	spin_lock(&kvm->mmu_lock);
-	if (!npages)
-		*memslot = old;
-	spin_unlock(&kvm->mmu_lock);
-#ifdef CONFIG_DMAR
-	/* map the pages in iommu page table */
-	r = kvm_iommu_map_pages(kvm, memslot);
-	if (r)
-		goto out;
-#endif
+	kvm_free_physmem_slot(&old, &new);
+	kfree(old_memslots);
+
+	if (flush_shadow)
+		kvm_arch_flush_shadow(kvm);
+
 	return 0;
 
 out_free:
@@ -768,7 +804,7 @@ EXPORT_SYMBOL_GPL(kvm_is_error_hva);
 struct kvm_memory_slot *gfn_to_memslot_unaliased(struct kvm *kvm, gfn_t gfn)
 {
 	int i;
-	struct kvm_memslots *slots = kvm->memslots;
+	struct kvm_memslots *slots = rcu_dereference(kvm->memslots);
 
 	for (i = 0; i < slots->nmemslots; ++i) {
 		struct kvm_memory_slot *memslot = &slots->memslots[i];
@@ -790,12 +826,15 @@ struct kvm_memory_slot *gfn_to_memslot(s
 int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
 {
 	int i;
-	struct kvm_memslots *slots = kvm->memslots;
+	struct kvm_memslots *slots = rcu_dereference(kvm->memslots);
 
 	gfn = unalias_gfn(kvm, gfn);
 	for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
 		struct kvm_memory_slot *memslot = &slots->memslots[i];
 
+		if (memslot->flags & KVM_MEMSLOT_INVALID)
+			continue;
+
 		if (gfn >= memslot->base_gfn
 		    && gfn < memslot->base_gfn + memslot->npages)
 			return 1;
@@ -810,7 +849,7 @@ unsigned long gfn_to_hva(struct kvm *kvm
 
 	gfn = unalias_gfn(kvm, gfn);
 	slot = gfn_to_memslot_unaliased(kvm, gfn);
-	if (!slot)
+	if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
 		return bad_hva();
 	return (slot->userspace_addr + (gfn - slot->base_gfn) * PAGE_SIZE);
 }
Index: kvm-slotslock/arch/ia64/kvm/kvm-ia64.c
===================================================================
--- kvm-slotslock.orig/arch/ia64/kvm/kvm-ia64.c
+++ kvm-slotslock/arch/ia64/kvm/kvm-ia64.c
@@ -1834,6 +1834,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kv
 	struct kvm_memory_slot *memslot;
 	int is_dirty = 0;
 
+	down_write(&kvm->slots_lock);
 	spin_lock(&kvm->arch.dirty_log_lock);
 
 	r = kvm_ia64_sync_dirty_log(kvm, log);
@@ -1853,6 +1854,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kv
 	}
 	r = 0;
 out:
+	up_write(&kvm->slots_lock);
 	spin_unlock(&kvm->arch.dirty_log_lock);
 	return r;
 }
Index: kvm-slotslock/arch/x86/kvm/mmu.c
===================================================================
--- kvm-slotslock.orig/arch/x86/kvm/mmu.c
+++ kvm-slotslock/arch/x86/kvm/mmu.c
@@ -29,6 +29,7 @@
 #include <linux/swap.h>
 #include <linux/hugetlb.h>
 #include <linux/compiler.h>
+#include <linux/srcu.h>
 
 #include <asm/page.h>
 #include <asm/cmpxchg.h>
@@ -766,23 +767,18 @@ static int kvm_unmap_rmapp(struct kvm *k
 static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
 			  int (*handler)(struct kvm *kvm, unsigned long *rmapp))
 {
-	int i, j;
+	int i, j, idx;
 	int retval = 0;
-	struct kvm_memslots *slots = kvm->memslots;
+	struct kvm_memslots *slots;
+
+	idx = srcu_read_lock(&kvm->srcu);
+	slots = rcu_dereference(kvm->memslots);
 
-	/*
-	 * If mmap_sem isn't taken, we can look the memslots with only
-	 * the mmu_lock by skipping over the slots with userspace_addr == 0.
-	 */
 	for (i = 0; i < slots->nmemslots; i++) {
 		struct kvm_memory_slot *memslot = &slots->memslots[i];
 		unsigned long start = memslot->userspace_addr;
 		unsigned long end;
 
-		/* mmu_lock protects userspace_addr */
-		if (!start)
-			continue;
-
 		end = start + (memslot->npages << PAGE_SHIFT);
 		if (hva >= start && hva < end) {
 			gfn_t gfn_offset = (hva - start) >> PAGE_SHIFT;
@@ -797,6 +793,7 @@ static int kvm_handle_hva(struct kvm *kv
 			}
 		}
 	}
+	srcu_read_unlock(&kvm->srcu, idx);
 
 	return retval;
 }
@@ -2966,16 +2963,20 @@ nomem:
  */
 unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm)
 {
-	int i;
+	int i, idx;
 	unsigned int nr_mmu_pages;
 	unsigned int  nr_pages = 0;
+	struct kvm_memslots *slots;
 
-	for (i = 0; i < kvm->memslots->nmemslots; i++)
-		nr_pages += kvm->memslots->memslots[i].npages;
+	idx = srcu_read_lock(&kvm->srcu);
+	slots = rcu_dereference(kvm->memslots);
+	for (i = 0; i < slots->nmemslots; i++)
+		nr_pages += slots->memslots[i].npages;
 
 	nr_mmu_pages = nr_pages * KVM_PERMILLE_MMU_PAGES / 1000;
 	nr_mmu_pages = max(nr_mmu_pages,
 			(unsigned int) KVM_MIN_ALLOC_MMU_PAGES);
+	srcu_read_unlock(&kvm->srcu, idx);
 
 	return nr_mmu_pages;
 }
@@ -3241,10 +3242,12 @@ static void audit_mappings(struct kvm_vc
 static int count_rmaps(struct kvm_vcpu *vcpu)
 {
 	int nmaps = 0;
-	int i, j, k;
+	int i, j, k, idx;
 
+	idx = srcu_read_lock(&kvm->srcu);
+	slots = rcu_dereference(kvm->memslots);
 	for (i = 0; i < KVM_MEMORY_SLOTS; ++i) {
-		struct kvm_memory_slot *m = &vcpu->kvm->memslots->memslots[i];
+		struct kvm_memory_slot *m = &slots->memslots[i];
 		struct kvm_rmap_desc *d;
 
 		for (j = 0; j < m->npages; ++j) {
@@ -3267,6 +3270,7 @@ static int count_rmaps(struct kvm_vcpu *
 			}
 		}
 	}
+	srcu_read_unlock(&kvm->srcu, idx);
 	return nmaps;
 }
 
Index: kvm-slotslock/arch/x86/kvm/vmx.c
===================================================================
--- kvm-slotslock.orig/arch/x86/kvm/vmx.c
+++ kvm-slotslock/arch/x86/kvm/vmx.c
@@ -24,6 +24,7 @@
 #include <linux/mm.h>
 #include <linux/highmem.h>
 #include <linux/sched.h>
+#include <linux/srcu.h>
 #include <linux/moduleparam.h>
 #include <linux/ftrace_event.h>
 #include "kvm_cache_regs.h"
@@ -1465,10 +1466,18 @@ static void enter_pmode(struct kvm_vcpu 
 static gva_t rmode_tss_base(struct kvm *kvm)
 {
 	if (!kvm->arch.tss_addr) {
-		gfn_t base_gfn = kvm->memslots->memslots[0].base_gfn +
-				 kvm->memslots->memslots[0].npages - 3;
+		struct kvm_memslots *slots;
+		gfn_t base_gfn;
+		int idx;
+
+		idx = srcu_read_lock(&kvm->srcu);
+		slots = rcu_dereference(kvm->memslots);
+ 		base_gfn = slots->memslots[0].base_gfn +
+				 slots->memslots[0].npages - 3;
+		srcu_read_unlock(&kvm->srcu, idx);
 		return base_gfn << PAGE_SHIFT;
 	}
+
 	return kvm->arch.tss_addr;
 }
 
Index: kvm-slotslock/include/linux/kvm_host.h
===================================================================
--- kvm-slotslock.orig/include/linux/kvm_host.h
+++ kvm-slotslock/include/linux/kvm_host.h
@@ -163,6 +163,7 @@ struct kvm {
 	struct rw_semaphore slots_lock;
 	struct mm_struct *mm; /* userspace tied to this vm */
 	struct kvm_memslots *memslots;
+	struct srcu_struct srcu;
 #ifdef CONFIG_KVM_APIC_ARCHITECTURE
 	u32 bsp_vcpu_id;
 	struct kvm_vcpu *bsp_vcpu;
Index: kvm-slotslock/virt/kvm/assigned-dev.c
===================================================================
--- kvm-slotslock.orig/virt/kvm/assigned-dev.c
+++ kvm-slotslock/virt/kvm/assigned-dev.c
@@ -504,11 +504,11 @@ out:
 static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
 				      struct kvm_assigned_pci_dev *assigned_dev)
 {
-	int r = 0;
+	int r = 0, idx;
 	struct kvm_assigned_dev_kernel *match;
 	struct pci_dev *dev;
 
-	down_read(&kvm->slots_lock);
+	idx = srcu_read_lock(&kvm->srcu);
 	mutex_lock(&kvm->lock);
 
 	match = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head,
@@ -574,7 +574,7 @@ static int kvm_vm_ioctl_assign_device(st
 
 out:
 	mutex_unlock(&kvm->lock);
-	up_read(&kvm->slots_lock);
+	srcu_read_unlock(&kvm->srcu, idx);
 	return r;
 out_list_del:
 	list_del(&match->list);
@@ -586,7 +586,7 @@ out_put:
 out_free:
 	kfree(match);
 	mutex_unlock(&kvm->lock);
-	up_read(&kvm->slots_lock);
+	srcu_read_unlock(&kvm->srcu, idx);
 	return r;
 }
 
Index: kvm-slotslock/virt/kvm/iommu.c
===================================================================
--- kvm-slotslock.orig/virt/kvm/iommu.c
+++ kvm-slotslock/virt/kvm/iommu.c
@@ -78,7 +78,7 @@ static int kvm_iommu_map_memslots(struct
 	int i, r = 0;
 	struct kvm_memslots *slots;
 
-	slots = kvm->memslots;
+	slots = rcu_dereference(kvm->memslots);
 
 	for (i = 0; i < slots->nmemslots; i++) {
 		r = kvm_iommu_map_pages(kvm, &slots->memslots[i]);
@@ -214,7 +214,7 @@ static int kvm_iommu_unmap_memslots(stru
 	int i;
 	struct kvm_memslots *slots;
 
-	slots = kvm->memslots;
+	slots = rcu_dereference(kvm->memslots);
 
 	for (i = 0; i < slots->nmemslots; i++) {
 		kvm_iommu_put_pages(kvm, slots->memslots[i].base_gfn,



  parent reply index

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-09-21 23:37 [patch 00/10] RFC: switch vcpu context to use SRCU Marcelo Tosatti
2009-09-21 23:37 ` [patch 01/10] KVM: modify memslots layout in struct kvm Marcelo Tosatti
2009-09-21 23:37 ` [patch 02/10] KVM: modify alias layout in x86s struct kvm_arch Marcelo Tosatti
2009-09-21 23:37 ` [patch 03/10] KVM: switch dirty_log to mmu_lock protection Marcelo Tosatti
2009-09-22  6:37   ` Avi Kivity
2009-09-22 12:44     ` Marcelo Tosatti
2009-09-22 12:52       ` Avi Kivity
2009-09-21 23:37 ` [patch 04/10] KVM: split kvm_arch_set_memory_region into prepare and commit Marcelo Tosatti
2009-09-22  6:40   ` Avi Kivity
2009-09-21 23:37 ` [patch 05/10] KVM: introduce gfn_to_pfn_memslot Marcelo Tosatti
2009-09-21 23:37 ` [patch 06/10] KVM: use gfn_to_pfn_memslot in kvm_iommu_map_pages Marcelo Tosatti
2009-09-21 23:37 ` Marcelo Tosatti [this message]
2009-09-22  6:59   ` [patch 07/10] KVM: introduce kvm->srcu and convert kvm_set_memory_region to SRCU update Avi Kivity
2009-09-22 16:16     ` Marcelo Tosatti
2009-09-22 10:40   ` Fernando Carrijo
2009-09-22 12:55     ` Marcelo Tosatti
2009-09-24 14:06   ` Marcelo Tosatti
2009-09-24 17:28     ` Paul E. McKenney
2009-09-24 18:05       ` Marcelo Tosatti
2009-09-25 15:05       ` Avi Kivity
2009-09-21 23:37 ` [patch 08/10] KVM: x86: switch kvm_set_memory_alias " Marcelo Tosatti
2009-09-22  7:04   ` Avi Kivity
2009-09-21 23:37 ` [patch 09/10] KVM: convert io_bus to SRCU Marcelo Tosatti
2009-09-21 23:37 ` [patch 10/10] KVM: switch vcpu context to use SRCU Marcelo Tosatti
2009-09-22  7:07   ` Avi Kivity
2009-09-22  7:09 ` [patch 00/10] RFC: " Avi Kivity

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