mm: always have io_remap_pfn_range() set pgprot_decrypted()

The purpose of io_remap_pfn_range() is to map IO memory, such as a
memory mapped IO exposed through a PCI BAR.  IO devices do not
understand encryption, so this memory must always be decrypted.
Automatically call pgprot_decrypted() as part of the generic
implementation.

This fixes a bug where enabling AMD SME causes subsystems, such as RDMA,
using io_remap_pfn_range() to expose BAR pages to user space to fail.
The CPU will encrypt access to those BAR pages instead of passing
unencrypted IO directly to the device.

Places not mapping IO should use remap_pfn_range().

Fixes: aca20d546214 ("x86/mm: Add support to make use of Secure Memory Encryption")
Signed-off-by: Jason Gunthorpe <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Tom Lendacky <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Brijesh Singh <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: "Dave Young" <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Larry Woodman <[email protected]>
Cc: Matt Fleming <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Toshimitsu Kani <[email protected]>
Cc: <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

2 files changed, 9 insertions, 4 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index ef360fe70aaf..db6ae4d3fb4e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2759,6 +2759,15 @@ static inline vm_fault_t vmf_insert_page(struct vm_area_struct *vma,
 	return VM_FAULT_NOPAGE;
 }
 
+#ifndef io_remap_pfn_range
+static inline int io_remap_pfn_range(struct vm_area_struct *vma,
+				     unsigned long addr, unsigned long pfn,
+				     unsigned long size, pgprot_t prot)
+{
+	return remap_pfn_range(vma, addr, pfn, size, pgprot_decrypted(prot));
+}
+#endif
+
 static inline vm_fault_t vmf_error(int err)
 {
 	if (err == -ENOMEM)
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 38c33eabea89..71125a4676c4 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1427,10 +1427,6 @@ typedef unsigned int pgtbl_mod_mask;
 
 #endif /* !__ASSEMBLY__ */
 
-#ifndef io_remap_pfn_range
-#define io_remap_pfn_range remap_pfn_range
-#endif
-
 #ifndef has_transparent_hugepage
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 #define has_transparent_hugepage() 1