From: Jason Gunthorpe <jgg@nvidia.com>
Date: Sun, 1 Nov 2020 17:08:00 -0800
Subject: mm: always have io_remap_pfn_range() set pgprot_decrypted()
Git-commit: f8f6ae5d077a9bdaf5cbf2ac960a5d1a04b47482
Patch-mainline: v5.10-rc3
References: bsc#1112178

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 <jgg@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: "Dave Young" <dyoung@redhat.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Larry Woodman <lwoodman@redhat.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Toshimitsu Kani <toshi.kani@hpe.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/0-v1-025d64bdf6c4+e-amd_sme_fix_jgg@nvidia.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Borislav Petkov <bp@suse.de>
---
 include/asm-generic/pgtable.h |    4 ----
 include/linux/mm.h            |    9 +++++++++
 2 files changed, 9 insertions(+), 4 deletions(-)

--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -993,10 +993,6 @@ static inline void init_espfix_bsp(void)
 
 #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
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2489,6 +2489,15 @@ struct page *follow_page_mask(struct vm_
 			      unsigned long address, unsigned int foll_flags,
 			      unsigned int *page_mask);
 
+#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 struct page *follow_page(struct vm_area_struct *vma,
 		unsigned long address, unsigned int foll_flags)
 {