lkml.org 
[lkml]   [2010]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 31/40] KVM: introduce kvm->srcu and convert kvm_set_memory_region to SRCU update
Date
From: Marcelo Tosatti <mtosatti@redhat.com>

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>
---
arch/ia64/kvm/kvm-ia64.c | 4 +-
arch/x86/kvm/mmu.c | 28 +++++-----
arch/x86/kvm/vmx.c | 6 ++-
include/linux/kvm.h | 2 +-
include/linux/kvm_host.h | 7 +--
virt/kvm/assigned-dev.c | 8 +-
virt/kvm/iommu.c | 4 +-
virt/kvm/kvm_main.c | 141 ++++++++++++++++++++++++++++++++++------------
8 files changed, 136 insertions(+), 64 deletions(-)

diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index 0757c70..b2e4d16 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -1382,7 +1382,7 @@ static void kvm_release_vm_pages(struct kvm *kvm)
int i, j;
unsigned long base_gfn;

- slots = kvm->memslots;
+ slots = rcu_dereference(kvm->memslots);
for (i = 0; i < slots->nmemslots; i++) {
memslot = &slots->memslots[i];
base_gfn = memslot->base_gfn;
@@ -1837,6 +1837,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
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);
@@ -1856,6 +1857,7 @@ int kvm_vm_ioctl_get_dirty_log(struct kvm *kvm,
}
r = 0;
out:
+ up_write(&kvm->slots_lock);
spin_unlock(&kvm->arch.dirty_log_lock);
return r;
}
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 81f84d3..f8bf42a 100644
--- a/arch/x86/kvm/mmu.c
+++ b/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>
@@ -807,21 +808,15 @@ static int kvm_handle_hva(struct kvm *kvm, unsigned long hva,
{
int i, j;
int retval = 0;
- struct kvm_memslots *slots = kvm->memslots;
+ struct kvm_memslots *slots;
+
+ 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;
@@ -1617,7 +1612,7 @@ static void mmu_unshadow(struct kvm *kvm, gfn_t gfn)

static void page_header_update_slot(struct kvm *kvm, void *pte, gfn_t gfn)
{
- int slot = memslot_id(kvm, gfn_to_memslot(kvm, gfn));
+ int slot = memslot_id(kvm, gfn);
struct kvm_mmu_page *sp = page_header(__pa(pte));

__set_bit(slot, sp->slot_bitmap);
@@ -3021,9 +3016,11 @@ unsigned int kvm_mmu_calculate_mmu_pages(struct kvm *kvm)
int i;
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;
+ 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,
@@ -3293,10 +3290,12 @@ static void audit_mappings(struct kvm_vcpu *vcpu)
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) {
@@ -3319,6 +3318,7 @@ static int count_rmaps(struct kvm_vcpu *vcpu)
}
}
}
+ srcu_read_unlock(&kvm->srcu, idx);
return nmaps;
}

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 1869879..f1cae7d 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1503,7 +1503,11 @@ static void enter_pmode(struct kvm_vcpu *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 +
+ struct kvm_memslots *slots;
+ gfn_t base_gfn;
+
+ slots = rcu_dereference(kvm->memslots);
+ base_gfn = kvm->memslots->memslots[0].base_gfn +
kvm->memslots->memslots[0].npages - 3;
return base_gfn << PAGE_SHIFT;
}
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index a24de0b..f2feef6 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -103,7 +103,7 @@ 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 {
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 9af2403..93bd307 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -162,6 +162,7 @@ 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;
@@ -275,6 +276,7 @@ void kvm_set_page_accessed(struct page *page);
pfn_t gfn_to_pfn(struct kvm *kvm, gfn_t gfn);
pfn_t gfn_to_pfn_memslot(struct kvm *kvm,
struct kvm_memory_slot *slot, gfn_t gfn);
+int memslot_id(struct kvm *kvm, gfn_t gfn);
void kvm_release_pfn_dirty(pfn_t);
void kvm_release_pfn_clean(pfn_t pfn);
void kvm_set_pfn_dirty(pfn_t pfn);
@@ -490,11 +492,6 @@ static inline void kvm_guest_exit(void)
current->flags &= ~PF_VCPU;
}

-static inline int memslot_id(struct kvm *kvm, struct kvm_memory_slot *slot)
-{
- return slot - kvm->memslots->memslots;
-}
-
static inline gpa_t gfn_to_gpa(gfn_t gfn)
{
return (gpa_t)gfn << PAGE_SHIFT;
diff --git a/virt/kvm/assigned-dev.c b/virt/kvm/assigned-dev.c
index f73de63..f51e684 100644
--- a/virt/kvm/assigned-dev.c
+++ b/virt/kvm/assigned-dev.c
@@ -504,12 +504,12 @@ 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;

mutex_lock(&kvm->lock);
- down_read(&kvm->slots_lock);
+ idx = srcu_read_lock(&kvm->srcu);

match = kvm_find_assigned_dev(&kvm->arch.assigned_dev_head,
assigned_dev->assigned_dev_id);
@@ -573,7 +573,7 @@ static int kvm_vm_ioctl_assign_device(struct kvm *kvm,
}

out:
- up_read(&kvm->slots_lock);
+ srcu_read_unlock(&kvm->srcu, idx);
mutex_unlock(&kvm->lock);
return r;
out_list_del:
@@ -585,7 +585,7 @@ out_put:
pci_dev_put(dev);
out_free:
kfree(match);
- up_read(&kvm->slots_lock);
+ srcu_read_unlock(&kvm->srcu, idx);
mutex_unlock(&kvm->lock);
return r;
}
diff --git a/virt/kvm/iommu.c b/virt/kvm/iommu.c
index cf567d8..65a5143 100644
--- a/virt/kvm/iommu.c
+++ b/virt/kvm/iommu.c
@@ -78,7 +78,7 @@ static int kvm_iommu_map_memslots(struct kvm *kvm)
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(struct kvm *kvm)
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,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 87d296d..2bb24a8 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -44,6 +44,7 @@
#include <linux/bitops.h>
#include <linux/spinlock.h>
#include <linux/compat.h>
+#include <linux/srcu.h>

#include <asm/processor.h>
#include <asm/io.h>
@@ -213,7 +214,7 @@ static void kvm_mmu_notifier_invalidate_page(struct mmu_notifier *mn,
unsigned long address)
{
struct kvm *kvm = mmu_notifier_to_kvm(mn);
- int need_tlb_flush;
+ int need_tlb_flush, idx;

/*
* When ->invalidate_page runs, the linux pte has been zapped
@@ -233,10 +234,12 @@ static void kvm_mmu_notifier_invalidate_page(struct mmu_notifier *mn,
* pte after kvm_unmap_hva returned, without noticing the page
* is going to be freed.
*/
+ idx = srcu_read_lock(&kvm->srcu);
spin_lock(&kvm->mmu_lock);
kvm->mmu_notifier_seq++;
need_tlb_flush = kvm_unmap_hva(kvm, address);
spin_unlock(&kvm->mmu_lock);
+ srcu_read_unlock(&kvm->srcu, idx);

/* we've to flush the tlb before the pages can be freed */
if (need_tlb_flush)
@@ -250,11 +253,14 @@ static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn,
pte_t pte)
{
struct kvm *kvm = mmu_notifier_to_kvm(mn);
+ int idx;

+ idx = srcu_read_lock(&kvm->srcu);
spin_lock(&kvm->mmu_lock);
kvm->mmu_notifier_seq++;
kvm_set_spte_hva(kvm, address, pte);
spin_unlock(&kvm->mmu_lock);
+ srcu_read_unlock(&kvm->srcu, idx);
}

static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
@@ -263,8 +269,9 @@ static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
unsigned long end)
{
struct kvm *kvm = mmu_notifier_to_kvm(mn);
- int need_tlb_flush = 0;
+ int need_tlb_flush = 0, idx;

+ idx = srcu_read_lock(&kvm->srcu);
spin_lock(&kvm->mmu_lock);
/*
* The count increase must become visible at unlock time as no
@@ -275,6 +282,7 @@ static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
for (; start < end; start += PAGE_SIZE)
need_tlb_flush |= kvm_unmap_hva(kvm, start);
spin_unlock(&kvm->mmu_lock);
+ srcu_read_unlock(&kvm->srcu, idx);

/* we've to flush the tlb before the pages can be freed */
if (need_tlb_flush)
@@ -312,11 +320,13 @@ static int kvm_mmu_notifier_clear_flush_young(struct mmu_notifier *mn,
unsigned long address)
{
struct kvm *kvm = mmu_notifier_to_kvm(mn);
- int young;
+ int young, idx;

+ idx = srcu_read_lock(&kvm->srcu);
spin_lock(&kvm->mmu_lock);
young = kvm_age_hva(kvm, address);
spin_unlock(&kvm->mmu_lock);
+ srcu_read_unlock(&kvm->srcu, idx);

if (young)
kvm_flush_remote_tlbs(kvm);
@@ -379,11 +389,15 @@ 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);
@@ -391,6 +405,7 @@ static struct kvm *kvm_create_vm(void)

r = kvm_init_mmu_notifier(kvm);
if (r) {
+ cleanup_srcu_struct(&kvm->srcu);
#ifdef KVM_COALESCED_MMIO_PAGE_OFFSET
put_page(page);
#endif
@@ -480,6 +495,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
#else
kvm_arch_flush_shadow(kvm);
#endif
+ cleanup_srcu_struct(&kvm->srcu);
kvm_arch_destroy_vm(kvm);
hardware_disable_all();
mmdrop(mm);
@@ -521,12 +537,13 @@ int __kvm_set_memory_region(struct kvm *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 */
@@ -588,15 +605,7 @@ int __kvm_set_memory_region(struct kvm *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;
@@ -651,8 +660,9 @@ 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;
@@ -660,34 +670,72 @@ skip_lpage:
new.userspace_addr = mem->userspace_addr;
#endif /* not defined CONFIG_S390 */

- if (!npages)
+ if (!npages) {
+ r = -ENOMEM;
+ 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_expedited(&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, mem, 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);
+ r = -ENOMEM;
+ 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_expedited(&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:
@@ -787,7 +835,7 @@ 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];
@@ -809,12 +857,15 @@ struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
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;
@@ -823,13 +874,31 @@ int kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
}
EXPORT_SYMBOL_GPL(kvm_is_visible_gfn);

+int memslot_id(struct kvm *kvm, gfn_t gfn)
+{
+ int i;
+ struct kvm_memslots *slots = rcu_dereference(kvm->memslots);
+ struct kvm_memory_slot *memslot = NULL;
+
+ gfn = unalias_gfn(kvm, gfn);
+ for (i = 0; i < slots->nmemslots; ++i) {
+ memslot = &slots->memslots[i];
+
+ if (gfn >= memslot->base_gfn
+ && gfn < memslot->base_gfn + memslot->npages)
+ break;
+ }
+
+ return memslot - slots->memslots;
+}
+
unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn)
{
struct kvm_memory_slot *slot;

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);
}
--
1.6.5.3


\
 
 \ /
  Last update: 2010-02-10 18:31    [W:0.110 / U:4.756 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site