[PATCH v5 05/16] x86/tdx: Add helper to do MapGPA hypercall

[Kuppuswamy Sathyanarayanan]

From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>

MapGPA hypercall is used by TDX guests to request VMM convert the
existing mapping of given GPA address range between private/shared.

tdx_hcall_gpa_intent() is the wrapper used for making MapGPA hypercall.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
---

Changes since v4:
 * Added required comments in tdx_hcall_gpa_intent().

Changes since v3:
 * None

Changes since v1:
 * Modified tdx_hcall_gpa_intent() to use _tdx_hypercall() instead of
   tdx_hypercall().

 arch/x86/include/asm/tdx.h | 18 ++++++++++++++++++
 arch/x86/kernel/tdx.c      | 30 ++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)

diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index b8f758dbbea9..a931c317e37d 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -56,6 +56,15 @@ struct ve_info {
 	u32 instr_info;
 };
 
+/*
+ * Page mapping type enum. This is software construct not
+ * part of any hardware or VMM ABI.
+ */
+enum tdx_map_type {
+	TDX_MAP_PRIVATE,
+	TDX_MAP_SHARED,
+};
+
 #ifdef CONFIG_INTEL_TDX_GUEST
 
 bool is_tdx_guest(void);
@@ -78,6 +87,9 @@ bool tdx_early_handle_ve(struct pt_regs *regs);
 
 extern phys_addr_t tdx_shared_mask(void);
 
+extern int tdx_hcall_gpa_intent(phys_addr_t gpa, int numpages,
+				enum tdx_map_type map_type);
+
 /*
  * To support I/O port access in decompressor or early kernel init
  * code, since #VE exception handler cannot be used, use paravirt
@@ -145,6 +157,12 @@ static inline bool tdx_early_handle_ve(struct pt_regs *regs) { return false; }
 
 static inline phys_addr_t tdx_shared_mask(void) { return 0; }
 
+static inline int tdx_hcall_gpa_intent(phys_addr_t gpa, int numpages,
+				       enum tdx_map_type map_type)
+{
+	return -ENODEV;
+}
+
 #endif /* CONFIG_INTEL_TDX_GUEST */
 
 #if defined(CONFIG_KVM_GUEST) && defined(CONFIG_INTEL_TDX_GUEST)
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 8a37ab0c6cbf..c3e4cc5d631b 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -17,6 +17,9 @@
 #define TDX_GET_INFO			1
 #define TDX_GET_VEINFO			3
 
+/* TDX hypercall Leaf IDs */
+#define TDVMCALL_MAP_GPA		0x10001
+
 #define VE_IS_IO_OUT(exit_qual)		(((exit_qual) & 8) ? 0 : 1)
 #define VE_GET_IO_SIZE(exit_qual)	(((exit_qual) & 7) + 1)
 #define VE_GET_PORT_NUM(exit_qual)	((exit_qual) >> 16)
@@ -105,6 +108,33 @@ static void tdx_get_info(void)
 	physical_mask &= ~tdx_shared_mask();
 }
 
+/*
+ * Inform the VMM of the guest's intent for this physical page:
+ * shared with the VMM or private to the guest.  The VMM is
+ * expected to change its mapping of the page in response.
+ *
+ * Note: shared->private conversions require further guest
+ * action to accept the page.
+ */
+int tdx_hcall_gpa_intent(phys_addr_t gpa, int numpages,
+			 enum tdx_map_type map_type)
+{
+	u64 ret;
+
+	if (map_type == TDX_MAP_SHARED)
+		gpa |= tdx_shared_mask();
+
+	/*
+	 * Notify VMM about page mapping conversion. More info
+	 * about ABI can be found in TDX Guest-Host-Communication
+	 * Interface (GHCI), sec 3.2.
+	 */
+	ret = _tdx_hypercall(TDVMCALL_MAP_GPA, gpa, PAGE_SIZE * numpages, 0, 0,
+			     NULL);
+
+	return ret ? -EIO : 0;
+}
+
 static __cpuidle void _tdx_halt(const bool irq_disabled, const bool do_sti)
 {
 	u64 ret;
-- 
2.25.1