linux-kernel - [tip:x86/asm] x86/mm: Use encrypted access of boot related data with SEV

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Date:   Tue, 7 Nov 2017 06:44:29 -0800
From:   tip-bot for Tom Lendacky <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     hpa@...or.com, labbott@...hat.com, matt@...eblueprint.co.uk,
        bp@...e.de, mingo@...nel.org, kirill.shutemov@...ux.intel.com,
        thomas.lendacky@....com, brijesh.singh@....com, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, bp@...en8.de, luto@...nel.org
Subject: [tip:x86/asm] x86/mm: Use encrypted access of boot related data
 with SEV

Commit-ID:  072f58c6ce29cf6cf429480fcd1b1e87d1d5ed18
Gitweb:     https://git.kernel.org/tip/072f58c6ce29cf6cf429480fcd1b1e87d1d5ed18
Author:     Tom Lendacky <thomas.lendacky@....com>
AuthorDate: Fri, 20 Oct 2017 09:30:47 -0500
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 7 Nov 2017 15:35:56 +0100

x86/mm: Use encrypted access of boot related data with SEV

When Secure Encrypted Virtualization (SEV) is active, boot data (such as
EFI related data, setup data) is encrypted and needs to be accessed as
such when mapped. Update the architecture override in early_memremap to
keep the encryption attribute when mapping this data.

Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Brijesh Singh <brijesh.singh@....com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Borislav Petkov <bp@...e.de>
Tested-by: Borislav Petkov <bp@...e.de>
Cc: Laura Abbott <labbott@...hat.com>
Cc: kvm@...r.kernel.org
Cc: Matt Fleming <matt@...eblueprint.co.uk>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Link: https://lkml.kernel.org/r/20171020143059.3291-6-brijesh.singh@amd.com

---
 arch/x86/mm/ioremap.c | 44 ++++++++++++++++++++++++++++++--------------
 1 file changed, 30 insertions(+), 14 deletions(-)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 34f0e18..52cc0f4 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -422,6 +422,9 @@ void unxlate_dev_mem_ptr(phys_addr_t phys, void *addr)
  * areas should be mapped decrypted. And since the encryption key can
  * change across reboots, persistent memory should also be mapped
  * decrypted.
+ *
+ * If SEV is active, that implies that BIOS/UEFI also ran encrypted so
+ * only persistent memory should be mapped decrypted.
  */
 static bool memremap_should_map_decrypted(resource_size_t phys_addr,
 					  unsigned long size)
@@ -458,6 +461,11 @@ static bool memremap_should_map_decrypted(resource_size_t phys_addr,
 	case E820_TYPE_ACPI:
 	case E820_TYPE_NVS:
 	case E820_TYPE_UNUSABLE:
+		/* For SEV, these areas are encrypted */
+		if (sev_active())
+			break;
+		/* Fallthrough */
+
 	case E820_TYPE_PRAM:
 		return true;
 	default:
@@ -581,7 +589,7 @@ static bool __init early_memremap_is_setup_data(resource_size_t phys_addr,
 bool arch_memremap_can_ram_remap(resource_size_t phys_addr, unsigned long size,
 				 unsigned long flags)
 {
-	if (!sme_active())
+	if (!mem_encrypt_active())
 		return true;
 
 	if (flags & MEMREMAP_ENC)
@@ -590,12 +598,13 @@ bool arch_memremap_can_ram_remap(resource_size_t phys_addr, unsigned long size,
 	if (flags & MEMREMAP_DEC)
 		return false;
 
-	if (memremap_is_setup_data(phys_addr, size) ||
-	    memremap_is_efi_data(phys_addr, size) ||
-	    memremap_should_map_decrypted(phys_addr, size))
-		return false;
+	if (sme_active()) {
+		if (memremap_is_setup_data(phys_addr, size) ||
+		    memremap_is_efi_data(phys_addr, size))
+			return false;
+	}
 
-	return true;
+	return !memremap_should_map_decrypted(phys_addr, size);
 }
 
 /*
@@ -608,17 +617,24 @@ pgprot_t __init early_memremap_pgprot_adjust(resource_size_t phys_addr,
 					     unsigned long size,
 					     pgprot_t prot)
 {
-	if (!sme_active())
+	bool encrypted_prot;
+
+	if (!mem_encrypt_active())
 		return prot;
 
-	if (early_memremap_is_setup_data(phys_addr, size) ||
-	    memremap_is_efi_data(phys_addr, size) ||
-	    memremap_should_map_decrypted(phys_addr, size))
-		prot = pgprot_decrypted(prot);
-	else
-		prot = pgprot_encrypted(prot);
+	encrypted_prot = true;
+
+	if (sme_active()) {
+		if (early_memremap_is_setup_data(phys_addr, size) ||
+		    memremap_is_efi_data(phys_addr, size))
+			encrypted_prot = false;
+	}
+
+	if (encrypted_prot && memremap_should_map_decrypted(phys_addr, size))
+		encrypted_prot = false;
 
-	return prot;
+	return encrypted_prot ? pgprot_encrypted(prot)
+			      : pgprot_decrypted(prot);
 }
 
 bool phys_mem_access_encrypted(unsigned long phys_addr, unsigned long size)