x86/sev: Add helper functions for RMPUPDATE and PSMASH instruction

The RMPUPDATE instruction updates the access restrictions for a page via
its corresponding entry in the RMP Table. The hypervisor will use the
instruction to enforce various access restrictions on pages used for
confidential guests and other specialized functionality. See APM3 for
details on the instruction operations.

The PSMASH instruction expands a 2MB RMP entry in the RMP table into a
corresponding set of contiguous 4KB RMP entries while retaining the
state of the validated bit from the original 2MB RMP entry. The
hypervisor will use this instruction in cases where it needs to re-map a
page as 4K rather than 2MB in a guest's nested page table.

Add helpers to make use of these instructions.

  [ mdr: add RMPUPDATE retry logic for transient FAIL_OVERLAP errors. ]

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Link: https://lore.kernel.org/r/20240126041126.1927228-11-michael.roth@amd.com

1 files changed, 23 insertions, 0 deletions

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 2c53e3de0b71..57fd95a5e6b2 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -87,10 +87,23 @@ extern bool handle_vc_boot_ghcb(struct pt_regs *regs);
 /* Software defined (when rFlags.CF = 1) */
 #define PVALIDATE_FAIL_NOUPDATE		255
 
+/* RMUPDATE detected 4K page and 2MB page overlap. */
+#define RMPUPDATE_FAIL_OVERLAP		4
+
 /* RMP page size */
 #define RMP_PG_SIZE_4K			0
 #define RMP_PG_SIZE_2M			1
 #define RMP_TO_PG_LEVEL(level)		(((level) == RMP_PG_SIZE_4K) ? PG_LEVEL_4K : PG_LEVEL_2M)
+#define PG_LEVEL_TO_RMP(level)		(((level) == PG_LEVEL_4K) ? RMP_PG_SIZE_4K : RMP_PG_SIZE_2M)
+
+struct rmp_state {
+	u64 gpa;
+	u8 assigned;
+	u8 pagesize;
+	u8 immutable;
+	u8 rsvd;
+	u32 asid;
+} __packed;
 
 #define RMPADJUST_VMSA_PAGE_BIT		BIT(16)
 
@@ -248,10 +261,20 @@ static inline u64 sev_get_status(void) { return 0; }
 bool snp_probe_rmptable_info(void);
 int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level);
 void snp_dump_hva_rmpentry(unsigned long address);
+int psmash(u64 pfn);
+int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, u32 asid, bool immutable);
+int rmp_make_shared(u64 pfn, enum pg_level level);
 #else
 static inline bool snp_probe_rmptable_info(void) { return false; }
 static inline int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) { return -ENODEV; }
 static inline void snp_dump_hva_rmpentry(unsigned long address) {}
+static inline int psmash(u64 pfn) { return -ENODEV; }
+static inline int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, u32 asid,
+				   bool immutable)
+{
+	return -ENODEV;
+}
+static inline int rmp_make_shared(u64 pfn, enum pg_level level) { return -ENODEV; }
 #endif
 
 #endif