[RFC v2 29/32] x86/tdx: Add helper to do MapGPA TDVMALL

[Kuppuswamy Sathyanarayanan]

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

MapGPA TDVMCALL requests the host VMM to map a GPA range as private or
shared memory mappings. Shared GPA mappings can be used for
communication beteen TD guest and host VMM, for example for
paravirtualized IO.

The new helper tdx_map_gpa() provides access to the operation.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/tdx.h | 13 +++++++++++++
 arch/x86/kernel/tdx.c      | 13 +++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index dc80cf7f7d08..4789798d7737 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -7,6 +7,11 @@
 
 #ifndef __ASSEMBLY__
 
+enum tdx_map_type {
+	TDX_MAP_PRIVATE,
+	TDX_MAP_SHARED,
+};
+
 #ifdef CONFIG_INTEL_TDX_GUEST
 
 #include <asm/cpufeature.h>
@@ -112,6 +117,8 @@ unsigned short tdg_inw(unsigned short port);
 unsigned int tdg_inl(unsigned short port);
 
 extern phys_addr_t tdg_shared_mask(void);
+extern int tdg_map_gpa(phys_addr_t gpa, int numpages,
+		       enum tdx_map_type map_type);
 
 #else // !CONFIG_INTEL_TDX_GUEST
 
@@ -155,6 +162,12 @@ static inline phys_addr_t tdg_shared_mask(void)
 {
 	return 0;
 }
+
+static inline int tdg_map_gpa(phys_addr_t gpa, int numpages,
+			      enum tdx_map_type map_type)
+{
+	return -ENODEV;
+}
 #endif /* CONFIG_INTEL_TDX_GUEST */
 #endif /* __ASSEMBLY__ */
 #endif /* _ASM_X86_TDX_H */
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 7e391cd7aa2b..074136473011 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -15,6 +15,8 @@
 #include "tdx-kvm.c"
 #endif
 
+#define TDVMCALL_MAP_GPA	0x10001
+
 static struct {
 	unsigned int gpa_width;
 	unsigned long attributes;
@@ -98,6 +100,17 @@ static void tdg_get_info(void)
 	physical_mask &= ~tdg_shared_mask();
 }
 
+int tdg_map_gpa(phys_addr_t gpa, int numpages, enum tdx_map_type map_type)
+{
+	u64 ret;
+
+	if (map_type == TDX_MAP_SHARED)
+		gpa |= tdg_shared_mask();
+
+	ret = tdvmcall(TDVMCALL_MAP_GPA, gpa, PAGE_SIZE * numpages, 0, 0);
+	return ret ? -EIO : 0;
+}
+
 static __cpuidle void tdg_halt(void)
 {
 	u64 ret;
-- 
2.25.1