[PATCH 13/18] KVM: x86/mmu: Avoid warning when installing non-private memory attributes

Nicolas Saenz Julienne
2024-06-09T15:57:30Z

In preparation to introducing RWX memory attributes, make sure
user-space is attempting to install a memory attribute with
KVM_MEMORY_ATTRIBUTE_PRIVATE before throwing a warning on systems with
no private memory support.

Signed-off-by: Nicolas Saenz Julienne <nsaenz@amazon.com>
---
arch/x86/kvm/mmu/mmu.c | 8 ++++++--
virt/kvm/kvm_main.c | 1 +
2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index b0c210b96419f..d56c04fbdc66b 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -7359,6 +7359,9 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
struct kvm_gfn_range *range)
{
+ unsigned long attrs = range->arg.attributes;
+ bool priv_attr = attrs & KVM_MEMORY_ATTRIBUTE_PRIVATE;
+
/*
* 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
@@ -7370,7 +7373,7 @@ bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
* 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)))
+ if (WARN_ON_ONCE(priv_attr && !kvm_arch_has_private_mem(kvm)))
return false;

return kvm_unmap_gfn_range(kvm, range);
@@ -7415,6 +7418,7 @@ bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
struct kvm_gfn_range *range)
{
unsigned long attrs = range->arg.attributes;
+ bool priv_attr = attrs & KVM_MEMORY_ATTRIBUTE_PRIVATE;
struct kvm_memory_slot *slot = range->slot;
int level;

@@ -7427,7 +7431,7 @@ bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
* 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)))
+ if (WARN_ON_ONCE(priv_attr && !kvm_arch_has_private_mem(kvm)))
return false;

/*
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 14841acb8b959..63c4b6739edee 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2506,6 +2506,7 @@ static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
struct kvm_mmu_notifier_range pre_set_range = {
.start = start,
.end = end,
+ .arg.attributes = attributes,
.handler = kvm_pre_set_memory_attributes,
.on_lock = kvm_mmu_invalidate_begin,
.flush_on_ret = true,
--
2.40.1