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Message-ID: <50e8f0950e00ec11385e5ce26764f95db80a973a.1747368093.git.afranji@google.com>
Date: Fri, 16 May 2025 19:19:31 +0000
From: Ryan Afranji <afranji@...gle.com>
To: afranji@...gle.com, ackerleytng@...gle.com, pbonzini@...hat.com,
seanjc@...gle.com, tglx@...utronix.de, x86@...nel.org, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
tabba@...gle.com
Cc: mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com,
shuah@...nel.org, andrew.jones@...ux.dev, ricarkol@...gle.com,
chao.p.peng@...ux.intel.com, jarkko@...nel.org, yu.c.zhang@...ux.intel.com,
vannapurve@...gle.com, erdemaktas@...gle.com, mail@...iej.szmigiero.name,
vbabka@...e.cz, david@...hat.com, qperret@...gle.com, michael.roth@....com,
wei.w.wang@...el.com, liam.merwick@...cle.com, isaku.yamahata@...il.com,
kirill.shutemov@...ux.intel.com, sagis@...gle.com, jthoughton@...gle.com
Subject: [RFC PATCH v2 11/13] KVM: x86: Handle moving of memory context for
intra-host migration
From: Ackerley Tng <ackerleytng@...gle.com>
Migration of memory context involves moving lpage_info and
mem_attr_array from source to destination VM.
Co-developed-by: Sagi Shahar <sagis@...gle.com>
Signed-off-by: Sagi Shahar <sagis@...gle.com>
Co-developed-by: Vishal Annapurve <vannapurve@...gle.com>
Signed-off-by: Vishal Annapurve <vannapurve@...gle.com>
Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
Signed-off-by: Ryan Afranji <afranji@...gle.com>
---
arch/x86/kvm/x86.c | 110 +++++++++++++++++++++++++++++++++++++++
include/linux/kvm_host.h | 17 ++++++
virt/kvm/guest_memfd.c | 25 +++++++++
3 files changed, 152 insertions(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3a7e05c47aa8..887702781465 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4564,6 +4564,33 @@ void kvm_unlock_two_vms(struct kvm *dst_kvm, struct kvm *src_kvm)
}
EXPORT_SYMBOL_GPL(kvm_unlock_two_vms);
+static int kvm_lock_vm_memslots(struct kvm *dst_kvm, struct kvm *src_kvm)
+{
+ int r = -EINVAL;
+
+ if (dst_kvm == src_kvm)
+ return r;
+
+ r = -EINTR;
+ if (mutex_lock_killable(&dst_kvm->slots_lock))
+ return r;
+
+ if (mutex_lock_killable_nested(&src_kvm->slots_lock, SINGLE_DEPTH_NESTING))
+ goto unlock_dst;
+
+ return 0;
+
+unlock_dst:
+ mutex_unlock(&dst_kvm->slots_lock);
+ return r;
+}
+
+static void kvm_unlock_vm_memslots(struct kvm *dst_kvm, struct kvm *src_kvm)
+{
+ mutex_unlock(&src_kvm->slots_lock);
+ mutex_unlock(&dst_kvm->slots_lock);
+}
+
/*
* Read or write a bunch of msrs. All parameters are kernel addresses.
*
@@ -6597,6 +6624,78 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_event,
return 0;
}
+static bool memslot_configurations_match(struct kvm_memslots *src_slots,
+ struct kvm_memslots *dst_slots)
+{
+ struct kvm_memslot_iter src_iter;
+ struct kvm_memslot_iter dst_iter;
+
+ kvm_for_each_memslot_pair(&src_iter, src_slots, &dst_iter, dst_slots) {
+ if (src_iter.slot->base_gfn != dst_iter.slot->base_gfn ||
+ src_iter.slot->npages != dst_iter.slot->npages ||
+ src_iter.slot->flags != dst_iter.slot->flags)
+ return false;
+
+ if (kvm_slot_can_be_private(dst_iter.slot) &&
+ !kvm_gmem_params_match(src_iter.slot, dst_iter.slot))
+ return false;
+ }
+
+ /* There should be no more nodes to iterate if configurations match */
+ return !src_iter.node && !dst_iter.node;
+}
+
+static int kvm_move_memory_ctxt_from(struct kvm *dst, struct kvm *src)
+{
+ struct kvm_memslot_iter src_iter;
+ struct kvm_memslot_iter dst_iter;
+ struct kvm_memslots *src_slots, *dst_slots;
+ int i;
+
+ /* TODO: Do we also need to check consistency for as_id == SMM? */
+ src_slots = __kvm_memslots(src, 0);
+ dst_slots = __kvm_memslots(dst, 0);
+
+ if (!memslot_configurations_match(src_slots, dst_slots))
+ return -EINVAL;
+
+ /*
+ * Transferring lpage_info is an optimization, lpage_info can be rebuilt
+ * by the destination VM.
+ */
+ kvm_for_each_memslot_pair(&src_iter, src_slots, &dst_iter, dst_slots) {
+ for (i = 1; i < KVM_NR_PAGE_SIZES; ++i) {
+ unsigned long ugfn = dst_iter.slot->userspace_addr >> PAGE_SHIFT;
+ int level = i + 1;
+
+ /*
+ * If the gfn and userspace address are not aligned wrt each
+ * other, skip migrating lpage_info.
+ */
+ if ((dst_iter.slot->base_gfn ^ ugfn) &
+ (KVM_PAGES_PER_HPAGE(level) - 1))
+ continue;
+
+ kvfree(dst_iter.slot->arch.lpage_info[i - 1]);
+ dst_iter.slot->arch.lpage_info[i - 1] =
+ src_iter.slot->arch.lpage_info[i - 1];
+ src_iter.slot->arch.lpage_info[i - 1] = NULL;
+ }
+ }
+
+#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+ /*
+ * For VMs that don't use private memory, this will just be moving an
+ * empty xarray pointer.
+ */
+ dst->mem_attr_array.xa_head = src->mem_attr_array.xa_head;
+ src->mem_attr_array.xa_head = NULL;
+#endif
+
+ kvm_vm_dead(src);
+ return 0;
+}
+
static int kvm_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd)
{
int r;
@@ -6624,6 +6723,14 @@ static int kvm_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd)
if (r)
goto out_mark_migration_done;
+ r = kvm_lock_vm_memslots(kvm, source_kvm);
+ if (r)
+ goto out_unlock;
+
+ r = kvm_move_memory_ctxt_from(kvm, source_kvm);
+ if (r)
+ goto out_unlock_memslots;
+
/*
* Different types of VMs will allow userspace to define if moving
* encryption context should be required.
@@ -6633,6 +6740,9 @@ static int kvm_vm_move_enc_context_from(struct kvm *kvm, unsigned int source_fd)
r = kvm_x86_call(vm_move_enc_context_from)(kvm, source_kvm);
}
+out_unlock_memslots:
+ kvm_unlock_vm_memslots(kvm, source_kvm);
+out_unlock:
kvm_unlock_two_vms(kvm, source_kvm);
out_mark_migration_done:
kvm_mark_migration_done(kvm, source_kvm);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 0c1d637a6e7d..99abe9879856 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1197,6 +1197,16 @@ struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);
struct kvm_memslots *kvm_vcpu_memslots(struct kvm_vcpu *vcpu);
struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn);
+
+/* Iterate over a pair of memslots in gfn order until one of the trees end */
+#define kvm_for_each_memslot_pair(iter1, slots1, iter2, slots2) \
+ for (kvm_memslot_iter_start(iter1, slots1, 0), \
+ kvm_memslot_iter_start(iter2, slots2, 0); \
+ kvm_memslot_iter_is_valid(iter1, U64_MAX) && \
+ kvm_memslot_iter_is_valid(iter2, U64_MAX); \
+ kvm_memslot_iter_next(iter1), \
+ kvm_memslot_iter_next(iter2))
+
/*
* KVM_SET_USER_MEMORY_REGION ioctl allows the following operations:
* - create a new memory slot
@@ -2521,6 +2531,8 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
gfn_t gfn, kvm_pfn_t *pfn, struct page **page,
int *max_order);
+bool kvm_gmem_params_match(struct kvm_memory_slot *slot1,
+ struct kvm_memory_slot *slot2);
#else
static inline int kvm_gmem_get_pfn(struct kvm *kvm,
struct kvm_memory_slot *slot, gfn_t gfn,
@@ -2530,6 +2542,11 @@ static inline int kvm_gmem_get_pfn(struct kvm *kvm,
KVM_BUG_ON(1, kvm);
return -EIO;
}
+static inline bool kvm_gmem_params_match(struct kvm_memory_slot *slot1,
+ struct kvm_memory_slot *slot2)
+{
+ return false;
+}
#endif /* CONFIG_KVM_PRIVATE_MEM */
#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index d76bd1119198..1a4198c4a4dd 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -778,6 +778,31 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
}
EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn);
+bool kvm_gmem_params_match(struct kvm_memory_slot *slot1,
+ struct kvm_memory_slot *slot2)
+{
+ bool ret;
+ struct file *file1;
+ struct file *file2;
+
+ if (slot1->gmem.pgoff != slot2->gmem.pgoff)
+ return false;
+
+ file1 = kvm_gmem_get_file(slot1);
+ file2 = kvm_gmem_get_file(slot2);
+
+ ret = (file1 && file2 &&
+ file_inode(file1) == file_inode(file2));
+
+ if (file1)
+ fput(file1);
+ if (file2)
+ fput(file2);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(kvm_gmem_params_match);
+
#ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM
long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long npages,
kvm_gmem_populate_cb post_populate, void *opaque)
--
2.49.0.1101.gccaa498523-goog
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