[PATCH v6 01/21] x86/tdx: Use enum to define page level of TDX supported page sizes

[Kai Huang <kai.huang@intel.com>]

TDX supports 4K, 2M and 1G page sizes.  When TDX guest accepts one page
via try_accept_one(), it passes the page size level to the TDX module.
Currently try_accept_one() uses hard-coded magic number for that.

Introduce a new enum type to represent the page level of TDX supported
page sizes to replace the hard-coded values.  Both initializing the TDX
module and KVM TDX support will need to use that too.

Also, currently try_accept_one() uses an open-coded switch statement to
get the TDX page level from the kernel page level.  As KVM will also
need to do the same thing, introduce a common helper to convert the
kernel page level to the TDX page level.

Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Kai Huang <kai.huang@intel.com>
---
 arch/x86/coco/tdx/tdx.c    | 20 ++++----------------
 arch/x86/include/asm/tdx.h | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 16 deletions(-)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 928dcf7a20d9..c5ff9647213d 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -655,7 +655,6 @@ static bool try_accept_one(phys_addr_t *start, unsigned long len,
 {
 	unsigned long accept_size = page_level_size(pg_level);
 	u64 tdcall_rcx;
-	u8 page_size;
 
 	if (!IS_ALIGNED(*start, accept_size))
 		return false;
@@ -663,27 +662,16 @@ static bool try_accept_one(phys_addr_t *start, unsigned long len,
 	if (len < accept_size)
 		return false;
 
+	/* TDX only supports 4K/2M/1G page sizes */
+	if (pg_level < PG_LEVEL_4K || pg_level > PG_LEVEL_1G)
+		return false;
 	/*
 	 * Pass the page physical address to the TDX module to accept the
 	 * pending, private page.
 	 *
 	 * Bits 2:0 of RCX encode page size: 0 - 4K, 1 - 2M, 2 - 1G.
 	 */
-	switch (pg_level) {
-	case PG_LEVEL_4K:
-		page_size = 0;
-		break;
-	case PG_LEVEL_2M:
-		page_size = 1;
-		break;
-	case PG_LEVEL_1G:
-		page_size = 2;
-		break;
-	default:
-		return false;
-	}
-
-	tdcall_rcx = *start | page_size;
+	tdcall_rcx = *start | to_tdx_pg_level(pg_level);
 	if (__tdx_module_call(TDX_ACCEPT_PAGE, tdcall_rcx, 0, 0, 0, NULL))
 		return false;
 
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 020c81a7c729..1c166fb9c22f 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -20,6 +20,39 @@
 
 #ifndef __ASSEMBLY__
 
+#include <asm/pgtable_types.h>
+
+/*
+ * The page levels of TDX supported page sizes (4K/2M/1G).
+ *
+ * Those values are part of the TDX module ABI.  Do not change them.
+ */
+enum tdx_pg_level {
+	TDX_PG_LEVEL_4K,
+	TDX_PG_LEVEL_2M,
+	TDX_PG_LEVEL_1G,
+	TDX_PG_LEVEL_NUM
+};
+
+/*
+ * Get the TDX page level based on the kernel page level.  The caller
+ * to make sure only pass 4K/2M/1G kernel page level.
+ */
+static inline enum tdx_pg_level to_tdx_pg_level(enum pg_level pglvl)
+{
+	switch (pglvl) {
+	case PG_LEVEL_4K:
+		return TDX_PG_LEVEL_4K;
+	case PG_LEVEL_2M:
+		return TDX_PG_LEVEL_2M;
+	case PG_LEVEL_1G:
+		return TDX_PG_LEVEL_1G;
+	default:
+		WARN_ON_ONCE(1);
+	}
+	return TDX_PG_LEVEL_NUM;
+}
+
 /*
  * Used to gather the output registers values of the TDCALL and SEAMCALL
  * instructions when requesting services from the TDX module.
-- 
2.37.3