[RFC PATCH 3/9] kvm_main.c: introduce kvm_internal_memory_region_list

Emanuele Giuseppe Esposito
2022-09-09T10:45:26Z

For now this struct is only used to pass new,old and change
variable in a single parameter instead of three.

In future, it will be used to also carry additional information
and handle atomic memslot updates.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
arch/x86/kvm/x86.c | 3 ++-
include/linux/kvm_host.h | 15 +++++++++++-
virt/kvm/kvm_main.c | 52 +++++++++++++++++++++++++++-------------
3 files changed, 51 insertions(+), 19 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 567d13405445..da5a5dd3d4bf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -12155,13 +12155,14 @@ void __user * __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa,

for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
struct kvm_userspace_memory_region m;
+ struct kvm_internal_memory_region_list b = { 0 };

m.slot = id | (i << 16);
m.flags = 0;
m.guest_phys_addr = gpa;
m.userspace_addr = hva;
m.memory_size = size;
- r = __kvm_set_memory_region(kvm, &m);
+ r = __kvm_set_memory_region(kvm, &m, &b);
if (r < 0)
return ERR_PTR_USR(r);
}
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 1c5b7b2e35dd..69af94472b39 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -1108,8 +1108,21 @@ enum kvm_mr_change {
KVM_MR_FLAGS_ONLY,
};

+/*
+ * Internally used to atomically update multiple memslots.
+ * Must be always zeroed by the caller.
+ */
+struct kvm_internal_memory_region_list {
+ /* Fields initialized in __kvm_set_memory_region() */
+ struct kvm_memory_slot *old;
+ struct kvm_memory_slot *new;
+ struct kvm_memory_slot *invalid;
+ enum kvm_mr_change change;
+};
+
int __kvm_set_memory_region(struct kvm *kvm,
- const struct kvm_userspace_memory_region *mem);
+ const struct kvm_userspace_memory_region *mem,
+ struct kvm_internal_memory_region_list *batch);
void kvm_arch_free_memslot(struct kvm *kvm, struct kvm_memory_slot *slot);
void kvm_arch_memslots_updated(struct kvm *kvm, u64 gen);
int kvm_arch_prepare_memory_region(struct kvm *kvm,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 339de0ed4557..e4fab15d0d4b 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1583,10 +1583,11 @@ static void kvm_swap_active_memslots(struct kvm *kvm, int as_id)
}

static int kvm_prepare_memory_region(struct kvm *kvm,
- const struct kvm_memory_slot *old,
- struct kvm_memory_slot *new,
- enum kvm_mr_change change)
+ struct kvm_internal_memory_region_list *batch)
{
+ struct kvm_memory_slot *old = batch->old;
+ struct kvm_memory_slot *new = batch->new;
+ enum kvm_mr_change change = batch->change;
int r;

/*
@@ -1621,10 +1622,12 @@ static int kvm_prepare_memory_region(struct kvm *kvm,
}

static void kvm_commit_memory_region(struct kvm *kvm,
- struct kvm_memory_slot *old,
- const struct kvm_memory_slot *new,
- enum kvm_mr_change change)
+ struct kvm_internal_memory_region_list *batch)
{
+ struct kvm_memory_slot *old = batch->old;
+ struct kvm_memory_slot *new = batch->new;
+ enum kvm_mr_change change = batch->change;
+
/*
* Update the total number of memslot pages before calling the arch
* hook so that architectures can consume the result directly.
@@ -1788,11 +1791,12 @@ static void kvm_update_flags_memslot(struct kvm *kvm,
}

static int kvm_set_memslot(struct kvm *kvm,
- struct kvm_memory_slot *old,
- struct kvm_memory_slot *new,
- enum kvm_mr_change change)
+ struct kvm_internal_memory_region_list *batch)
{
struct kvm_memory_slot *invalid_slot;
+ struct kvm_memory_slot *old = batch->old;
+ struct kvm_memory_slot *new = batch->new;
+ enum kvm_mr_change change = batch->change;
int r;

/*
@@ -1830,10 +1834,11 @@ static int kvm_set_memslot(struct kvm *kvm,
mutex_unlock(&kvm->slots_arch_lock);
return -ENOMEM;
}
+ batch->invalid = invalid_slot;
kvm_invalidate_memslot(kvm, old, invalid_slot);
}

- r = kvm_prepare_memory_region(kvm, old, new, change);
+ r = kvm_prepare_memory_region(kvm, batch);
if (r) {
/*
* For DELETE/MOVE, revert the above INVALID change. No
@@ -1877,7 +1882,7 @@ static int kvm_set_memslot(struct kvm *kvm,
* will directly hit the final, active memslot. Architectures are
* responsible for knowing that new->arch may be stale.
*/
- kvm_commit_memory_region(kvm, old, new, change);
+ kvm_commit_memory_region(kvm, batch);

return 0;
}
@@ -1900,11 +1905,14 @@ static bool kvm_check_memslot_overlap(struct kvm_memslots *slots, int id,
* space.
*
* Discontiguous memory is allowed, mostly for framebuffers.
+ * This function takes also care of initializing batch->new/old/invalid/change
+ * fields.
*
* Must be called holding kvm->slots_lock for write.
*/
int __kvm_set_memory_region(struct kvm *kvm,
- const struct kvm_userspace_memory_region *mem)
+ const struct kvm_userspace_memory_region *mem,
+ struct kvm_internal_memory_region_list *batch)
{
struct kvm_memory_slot *old, *new;
struct kvm_memslots *slots;
@@ -1947,6 +1955,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
* and/or destroyed by kvm_set_memslot().
*/
old = id_to_memslot(slots, id);
+ batch->old = old;

if (!mem->memory_size) {
if (!old || !old->npages)
@@ -1955,7 +1964,9 @@ int __kvm_set_memory_region(struct kvm *kvm,
if (WARN_ON_ONCE(kvm->nr_memslot_pages < old->npages))
return -EIO;

- return kvm_set_memslot(kvm, old, NULL, KVM_MR_DELETE);
+ batch->change = KVM_MR_DELETE;
+ batch->new = NULL;
+ return kvm_set_memslot(kvm, batch);
}

base_gfn = (mem->guest_phys_addr >> PAGE_SHIFT);
@@ -1963,6 +1974,7 @@ int __kvm_set_memory_region(struct kvm *kvm,

if (!old || !old->npages) {
change = KVM_MR_CREATE;
+ batch->old = NULL;

/*
* To simplify KVM internals, the total number of pages across
@@ -2000,7 +2012,10 @@ int __kvm_set_memory_region(struct kvm *kvm,
new->flags = mem->flags;
new->userspace_addr = mem->userspace_addr;

- r = kvm_set_memslot(kvm, old, new, change);
+ batch->new = new;
+ batch->change = change;
+
+ r = kvm_set_memslot(kvm, batch);
if (r)
kfree(new);
return r;
@@ -2008,7 +2023,8 @@ int __kvm_set_memory_region(struct kvm *kvm,
EXPORT_SYMBOL_GPL(__kvm_set_memory_region);

static int kvm_set_memory_region(struct kvm *kvm,
- const struct kvm_userspace_memory_region *mem)
+ const struct kvm_userspace_memory_region *mem,
+ struct kvm_internal_memory_region_list *batch)
{
int r;

@@ -2016,7 +2032,7 @@ static int kvm_set_memory_region(struct kvm *kvm,
return -EINVAL;

mutex_lock(&kvm->slots_lock);
- r = __kvm_set_memory_region(kvm, mem);
+ r = __kvm_set_memory_region(kvm, mem, batch);
mutex_unlock(&kvm->slots_lock);
return r;
}
@@ -2024,7 +2040,9 @@ static int kvm_set_memory_region(struct kvm *kvm,
static int kvm_vm_ioctl_set_memory_region(struct kvm *kvm,
struct kvm_userspace_memory_region *mem)
{
- return kvm_set_memory_region(kvm, mem);
+ struct kvm_internal_memory_region_list batch = { 0 };
+
+ return kvm_set_memory_region(kvm, mem, &batch);
}

#ifndef CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT
--
2.31.1