asm/io.h: Add ioremap_driver_hardening

This function is for declaring memory that should be shared with
a hypervisor in a confidential guest. If the architecture doesn't
implement it it's just ioremap.

Note this function is not supposed to be used directly by drivers.
But it will be used implicitly by pci_iomap -- based on the
authorized attribute -- and also by the PCI subsystem. To avoid
ifdefs we create a generic ioremap alias.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

Documentation/driver-api/device-io.rst

@@ -429,6 +429,17 @@ of the linear kernel memory area to a regular pointer.
 
 Portable drivers should avoid the use of ioremap_cache().
 
+ioremap_driver_hardened()
+-------------------------
+
+ioremap_driver_hardened() maps I/O memory so that it can be shared with the host
+in a confidential guest platform. It is mainly used in platforms like
+Trusted Domain Extensions (TDX).
+
+Drivers should not need to use this function directly, but instead use
+functions like pci_iomap_range(), which use it implicitly based on driver
+authorization.
+
 Architecture example
 --------------------
 

arch/alpha/include/asm/io.h

@@ -308,6 +308,8 @@ static inline void __iomem *ioremap(unsigned long port, unsigned long size)
 }
 
 #define ioremap_wc ioremap
+/* Share memory with host in confidential guest platforms */
+#define ioremap_driver_hardened ioremap
 #define ioremap_uc ioremap
 
 static inline void iounmap(volatile void __iomem *addr)

arch/mips/include/asm/io.h

@@ -170,6 +170,8 @@ void iounmap(const volatile void __iomem *addr);
 #define ioremap(offset, size)						\
 	ioremap_prot((offset), (size), _CACHE_UNCACHED)
 #define ioremap_uc		ioremap
+/* Share memory with host in confidential guest platforms */
+#define ioremap_driver_hardened	ioremap
 
 /*
  * ioremap_cache -	map bus memory into CPU space

arch/parisc/include/asm/io.h

@@ -127,6 +127,8 @@ static inline void gsc_writeq(unsigned long long val, unsigned long addr)
  */
 void __iomem *ioremap(unsigned long offset, unsigned long size);
 #define ioremap_wc			ioremap
+/* Share memory with host in confidential guest platforms */
+#define ioremap_driver_hardened		ioremap
 #define ioremap_uc			ioremap
 #define pci_iounmap			pci_iounmap
 

arch/sparc/include/asm/io_64.h

@@ -426,6 +426,8 @@ static inline void __iomem *ioremap(unsigned long offset, unsigned long size)
 #define ioremap_uc(X,Y)			ioremap((X),(Y))
 #define ioremap_wc(X,Y)			ioremap((X),(Y))
 #define ioremap_wt(X,Y)			ioremap((X),(Y))
+/* Share memory with host in confidential guest platforms */
+#define ioremap_driver_hardened(X, Y)	ioremap((X), (Y))
 static inline void __iomem *ioremap_np(unsigned long offset, unsigned long size)
 {
 	return NULL;

arch/x86/include/asm/io.h

@@ -325,6 +325,10 @@ extern void __iomem *ioremap_wc(resource_size_t offset, unsigned long size);
 extern void __iomem *ioremap_wt(resource_size_t offset, unsigned long size);
 #define ioremap_wt ioremap_wt
 
+extern void __iomem *ioremap_driver_hardened(resource_size_t offset,
+					 unsigned long size);
+#define ioremap_driver_hardened ioremap_driver_hardened
+
 extern bool is_early_ioremap_ptep(pte_t *ptep);
 
 #define IO_SPACE_LIMIT 0xffff

include/asm-generic/io.h

@@ -1092,6 +1092,11 @@ static inline void __iomem *ioremap(phys_addr_t addr, size_t size)
 #define ioremap_wt ioremap
 #endif
 
+/* Share memory with host in confidential guest platforms */
+#ifndef ioremap_driver_hardened
+#define ioremap_driver_hardened ioremap
+#endif
+
 /*
  * ioremap_uc is special in that we do require an explicit architecture
  * implementation.  In general you do not want to use this function in a