[PATCH v7 01/45] KVM: Prepare for handling only shared mappings in mmu_notifier events

Steven Price
2025-02-13T16:14:49Z

From: Sean Christopherson <seanjc@google.com>

Add flags to "struct kvm_gfn_range" to let notifier events target only
shared and only private mappings, and write up the existing mmu_notifier
events to be shared-only (private memory is never associated with a
userspace virtual address, i.e. can't be reached via mmu_notifiers).

Add two flags so that KVM can handle the three possibilities (shared,
private, and shared+private) without needing something like a tri-state
enum.

Link: https://lore.kernel.org/all/ZJX0hk+KpQP0KUyB@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Steven Price <steven.price@arm.com>
---
include/linux/kvm_host.h | 2 ++
virt/kvm/kvm_main.c | 7 +++++++
2 files changed, 9 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 3cb9a32a6330..0de1e485452c 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -266,6 +266,8 @@ struct kvm_gfn_range {
gfn_t end;
union kvm_mmu_notifier_arg arg;
enum kvm_gfn_range_filter attr_filter;
+ bool only_private;
+ bool only_shared;
bool may_block;
};
bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index faf10671eed2..4f0136094fac 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -593,6 +593,13 @@ static __always_inline kvm_mn_ret_t __kvm_handle_hva_range(struct kvm *kvm,
* the second or later invocation of the handler).
*/
gfn_range.arg = range->arg;
+
+ /*
+ * HVA-based notifications aren't relevant to private
+ * mappings as they don't have a userspace mapping.
+ */
+ gfn_range.only_private = false;
+ gfn_range.only_shared = true;
gfn_range.may_block = range->may_block;
/*
* HVA-based notifications aren't relevant to private
--
2.43.0