[tip: x86/tdx] x86/tdx: Make pages shared in ioremap()

[tip-bot2 for Kirill A. Shutemov]

The following commit has been merged into the x86/tdx branch of tip:

Commit-ID:     9aa6ea69852c46e551f4180dce4208bd53df418c
Gitweb:        https://git.kernel.org/tip/9aa6ea69852c46e551f4180dce4208bd53df418c
Author:        Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
AuthorDate:    Wed, 06 Apr 2022 02:29:34 +03:00
Committer:     Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Thu, 07 Apr 2022 08:27:53 -07:00

x86/tdx: Make pages shared in ioremap()

In TDX guests, guest memory is protected from host access. If a guest
performs I/O, it needs to explicitly share the I/O memory with the host.

Make all ioremap()ed pages that are not backed by normal memory
(IORES_DESC_NONE or IORES_DESC_RESERVED) mapped as shared.

The permissions in PAGE_KERNEL_IO already work for "decrypted" memory
on AMD SEV/SME systems.  That means that they have no need to make a
pgprot_decrypted() call.

TDX guests, on the other hand, _need_ change to PAGE_KERNEL_IO for
"decrypted" mappings.  Add a pgprot_decrypted() for TDX.

Co-developed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20220405232939.73860-26-kirill.shutemov@xxxxxxxxxxxxxxx
---
 arch/x86/mm/ioremap.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 17a492c..1ad0228 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -242,10 +242,15 @@ __ioremap_caller(resource_size_t phys_addr, unsigned long size,
 	 * If the page being mapped is in memory and SEV is active then
 	 * make sure the memory encryption attribute is enabled in the
 	 * resulting mapping.
+	 * In TDX guests, memory is marked private by default. If encryption
+	 * is not requested (using encrypted), explicitly set decrypt
+	 * attribute in all IOREMAPPED memory.
 	 */
 	prot = PAGE_KERNEL_IO;
 	if ((io_desc.flags & IORES_MAP_ENCRYPTED) || encrypted)
 		prot = pgprot_encrypted(prot);
+	else
+		prot = pgprot_decrypted(prot);
 
 	switch (pcm) {
 	case _PAGE_CACHE_MODE_UC: