[PATCH v3 12/21] KVM: arm64: Add helpers to tag shared pages in SW bits

Quentin Perret
2021-07-29T13:29:31Z

We will soon start annotating shared pages in page-tables in nVHE
protected mode. Define all the states in which a page can be (owned,
shared and owned, shared and borrowed), and provide helpers allowing to
convert this into SW bits annotations using the matching prot
attributes.

Signed-off-by: Quentin Perret <qperret@google.com>
---
arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 26 +++++++++++++++++++
1 file changed, 26 insertions(+)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
index 9c227d87c36d..ae355bfd8c01 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h
@@ -12,6 +12,32 @@
#include <asm/virt.h>
#include <nvhe/spinlock.h>

+/*
+ * SW bits 0-1 are reserved to track the memory ownership state of each page:
+ * 00: The page is owned solely by the page-table owner.
+ * 01: The page is owned by the page-table owner, but is shared
+ * with another entity.
+ * 10: The page is shared with, but not owned by the page-table owner.
+ * 11: Reserved for future use (lending).
+ */
+enum pkvm_page_state {
+ PKVM_PAGE_OWNED = 0ULL,
+ PKVM_PAGE_SHARED_OWNED = KVM_PGTABLE_PROT_SW0,
+ PKVM_PAGE_SHARED_BORROWED = KVM_PGTABLE_PROT_SW1,
+};
+
+#define PKVM_PAGE_STATE_PROT_MASK (KVM_PGTABLE_PROT_SW0 | KVM_PGTABLE_PROT_SW1)
+static inline enum kvm_pgtable_prot pkvm_mkstate(enum kvm_pgtable_prot prot,
+ enum pkvm_page_state state)
+{
+ return (prot & ~PKVM_PAGE_STATE_PROT_MASK) | state;
+}
+
+static inline enum pkvm_page_state pkvm_getstate(enum kvm_pgtable_prot prot)
+{
+ return prot & PKVM_PAGE_STATE_PROT_MASK;
+}
+
struct host_kvm {
struct kvm_arch arch;
struct kvm_pgtable pgt;
--
2.32.0.432.gabb21c7263-goog