linux-kernel - [PATCHv6 25/30] x86/tdx: Make pages shared in ioremap()

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Message-Id: <20220316020856.24435-26-kirill.shutemov@linux.intel.com>
Date:   Wed, 16 Mar 2022 05:08:51 +0300
From:   "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...el.com, luto@...nel.org, peterz@...radead.org
Cc:     sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
        ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
        hpa@...or.com, jgross@...e.com, jmattson@...gle.com,
        joro@...tes.org, jpoimboe@...hat.com, knsathya@...nel.org,
        pbonzini@...hat.com, sdeep@...are.com, seanjc@...gle.com,
        tony.luck@...el.com, vkuznets@...hat.com, wanpengli@...cent.com,
        thomas.lendacky@....com, brijesh.singh@....com, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCHv6 25/30] 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@...ux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 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 026031b3b782..a5d4ec1afca2 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:
-- 
2.34.1