[RFC PATCH v5 1/8] x86/sev: Define the #HV doorbell page structure

[Melody Wang]

Restricted injection is a feature which enforces additional interrupt
and event injection security protections for a SEV-SNP guest. It
disables all hypervisor-based interrupt queuing and event injection of
all vectors except a new exception vector, #HV (28), which is reserved
for SNP guest use, but never generated by hardware. #HV is only allowed
to be injected into VMSAs that execute with Restricted Injection.

The guests running with the SNP restricted injection feature active
limit the host to ringing a doorbell with a #HV exception.

Define two fields in the #HV doorbell page: a pending event field, and
an EOI assist.

Create the structure definition for the #HV doorbell page as per GHCB
specification.

Co-developed-by: Thomas Lendacky <thomas.lendacky@xxxxxxx>
Signed-off-by: Thomas Lendacky <thomas.lendacky@xxxxxxx>
Signed-off-by: Melody Wang <huibo.wang@xxxxxxx>
---
 arch/x86/include/asm/svm.h | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index aa63431ba92c..3b77eaac3d07 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -253,6 +253,39 @@ struct __attribute__ ((__packed__)) vmcb_control_area {
 #define SVM_TSC_RATIO_MAX	0x000000ffffffffffULL
 #define SVM_TSC_RATIO_DEFAULT	0x0100000000ULL
 
+/*
+ * Hypervisor doorbell page:
+ *
+ * Used when Restricted Injection is enabled for a VM. One page in size that
+ * is shared between the guest and hypervisor to communicate exception and
+ * interrupt events.
+ */
+struct hvdb_events {
+	/* First 64 bytes of HV doorbell page defined in GHCB specification */
+	union {
+		struct {
+			/* Non-maskable event indicators */
+			u16 vector:		8,
+			    nmi:		1,
+			    mce:		1,
+			    reserved2:		5,
+			    no_further_signal:	1;
+		};
+
+		u16 pending_events;
+	};
+
+	u8 no_eoi_required;
+
+	u8 reserved3[61];
+} __packed;
+
+struct hvdb {
+	struct hvdb_events events;
+
+	/* Remainder of the page is for software use */
+	u8 reserved[PAGE_SIZE - sizeof(struct hvdb_events)];
+} __packed;
 
 /* AVIC */
 #define AVIC_LOGICAL_ID_ENTRY_GUEST_PHYSICAL_ID_MASK	(0xFFULL)
@@ -569,6 +602,8 @@ static inline void __unused_size_checks(void)
 	BUILD_BUG_ON(sizeof(struct vmcb_control_area)	!= EXPECTED_VMCB_CONTROL_AREA_SIZE);
 	BUILD_BUG_ON(offsetof(struct vmcb, save)	!= EXPECTED_VMCB_CONTROL_AREA_SIZE);
 	BUILD_BUG_ON(sizeof(struct ghcb)		!= EXPECTED_GHCB_SIZE);
+	BUILD_BUG_ON(sizeof(struct hvdb_events)		!= 64);
+	BUILD_BUG_ON(sizeof(struct hvdb)		!= 4096);
 
 	/* Check offsets of reserved fields */
 
-- 
2.43.0