Re: [PATCH v3 12/21] KVM: arm64: Add helpers to tag shared pages in SW bits
From: Fuad Tabba <hidden>
Date: 2021-08-02 10:31:05
Also in:
kvmarm, lkml
Hi Quentin, On Thu, Jul 29, 2021 at 3:28 PM Quentin Perret [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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.
nit: solely -> exclusively, because "exclusive" is the more common term in context of shared resources
+ * 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;
+}
+I think that this encoding is pretty neat and easy to follow. Reviewed-by: Fuad Tabba <redacted> Thanks, /fuad
struct host_kvm {
struct kvm_arch arch;
struct kvm_pgtable pgt;
--
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