To make it useful for other use cases such as Heki, remove the private
memory optimizations.
I guess we could try to infer the applied attributes to get back these
optimizations when it makes sense, but let's keep this simple for now.
Main changes:
- Replace slots_lock with slots_arch_lock to make it callable from a KVM
hypercall.
- Move this mutex lock into kvm_vm_ioctl_set_mem_attributes() to make it
easier to use with other locks.
- Export kvm_vm_set_mem_attributes().
- Remove the kvm_arch_pre_set_memory_attributes() and
kvm_arch_post_set_memory_attributes() KVM_MEMORY_ATTRIBUTE_PRIVATE
optimizations.
Cc: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Madhavan T. Venkataraman <madvenka@xxxxxxxxxxxxxxxxxxx>
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Cc: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
Signed-off-by: Mickaël Salaün <mic@xxxxxxxxxxx>
---
Changes since v1:
* New patch
---
arch/x86/kvm/mmu/mmu.c | 23 -----------------------
include/linux/kvm_host.h | 2 ++
virt/kvm/kvm_main.c | 19 ++++++++++---------
3 files changed, 12 insertions(+), 32 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 7e053973125c..4d378d308762 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -7251,20 +7251,6 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
struct kvm_gfn_range *range)
{
- /*
- * Zap SPTEs even if the slot can't be mapped PRIVATE. KVM x86 only
- * supports KVM_MEMORY_ATTRIBUTE_PRIVATE, and so it *seems* like KVM
- * can simply ignore such slots. But if userspace is making memory
- * PRIVATE, then KVM must prevent the guest from accessing the memory
- * as shared. And if userspace is making memory SHARED and this point
- * is reached, then at least one page within the range was previously
- * PRIVATE, i.e. the slot's possible hugepage ranges are changing.
- * Zapping SPTEs in this case ensures KVM will reassess whether or not
- * a hugepage can be used for affected ranges.
- */
- if (WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm)))
- return false;
-
return kvm_unmap_gfn_range(kvm, range);
}
@@ -7313,15 +7299,6 @@ bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
lockdep_assert_held_write(&kvm->mmu_lock);
lockdep_assert_held(&kvm->slots_lock);
- /*
- * Calculate which ranges can be mapped with hugepages even if the slot
- * can't map memory PRIVATE. KVM mustn't create a SHARED hugepage over
- * a range that has PRIVATE GFNs, and conversely converting a range to
- * SHARED may now allow hugepages.
- */
- if (WARN_ON_ONCE(!kvm_arch_has_private_mem(kvm)))
- return false;
-
/*
* The sequence matters here: upper levels consume the result of lower
* level's scanning.
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index ec32af17add8..85b8648fd892 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2396,6 +2396,8 @@ bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
struct kvm_gfn_range *range);
bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
struct kvm_gfn_range *range);
+int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
+ unsigned long attributes);
static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
{
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 23633984142f..0096ccfbb609 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2552,7 +2552,7 @@ static bool kvm_pre_set_memory_attributes(struct kvm *kvm,
}
/* Set @attributes for the gfn range [@start, @end). */
-static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
+int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
unsigned long attributes)
{
struct kvm_mmu_notifier_range pre_set_range = {
@@ -2577,11 +2577,11 @@ static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
entry = attributes ? xa_mk_value(attributes) : NULL;
- mutex_lock(&kvm->slots_lock);
+ lockdep_assert_held(&kvm->slots_arch_lock);
/* Nothing to do if the entire range as the desired attributes. */
if (kvm_range_has_memory_attributes(kvm, start, end, attributes))
- goto out_unlock;
+ return r;
/*
* Reserve memory ahead of time to avoid having to deal with failures
@@ -2590,7 +2590,7 @@ static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
for (i = start; i < end; i++) {
r = xa_reserve(&kvm->mem_attr_array, i, GFP_KERNEL_ACCOUNT);
if (r)
- goto out_unlock;
+ return r;
}
kvm_handle_gfn_range(kvm, &pre_set_range);
@@ -2602,15 +2602,13 @@ static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
}
kvm_handle_gfn_range(kvm, &post_set_range);
-
-out_unlock:
- mutex_unlock(&kvm->slots_lock);
-
return r;
}
+
static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
struct kvm_memory_attributes *attrs)
{
+ int r;
gfn_t start, end;
/* flags is currently not used. */
@@ -2633,7 +2631,10 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
*/
BUILD_BUG_ON(sizeof(attrs->attributes) != sizeof(unsigned long));
- return kvm_vm_set_mem_attributes(kvm, start, end, attrs->attributes);
+ mutex_lock(&kvm->slots_arch_lock);
+ r = kvm_vm_set_mem_attributes(kvm, start, end, attrs->attributes);
+ mutex_unlock(&kvm->slots_arch_lock);
+ return r;
}
#endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */
--
2.42.1
