linux-kernel - [PATCH v3 1/7] x86/ioremap: Map efi_mem_reserve() memory as encrypted for SEV

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Date:   Tue,  8 Jun 2021 11:54:33 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     x86@...nel.org
Cc:     Joerg Roedel <joro@...tes.org>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>, hpa@...or.com,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Martin Radev <martin.b.radev@...il.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: [PATCH v3 1/7] x86/ioremap: Map efi_mem_reserve() memory as encrypted for SEV

From: Tom Lendacky <thomas.lendacky@....com>

Some drivers require memory that is marked as EFI boot services data. So that
this memory is not re-used by the kernel after ExitBootServices(),
efi_mem_reserve() is used to preserve it by inserting a new EFI memory
descriptor and marking it with the EFI_MEMORY_RUNTIME attribute.

Under SEV, memory marked with the EFI_MEMORY_RUNTIME attribute needs to
be mapped encrypted by Linux, otherwise the kernel might crash at boot
like below:

 EFI Variables Facility v0.08 2004-May-17
 general protection fault, probably for non-canonical address 0x3597688770a868b2: 0000 [#1] SMP NOPTI
 CPU: 13 PID: 1 Comm: swapper/0 Not tainted 5.12.4-2-default #1 openSUSE Tumbleweed
 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
 RIP: 0010:efi_mokvar_entry_next+0x34/0x40
 Code: c5 01 48 8b 17 48 c7 07 00 00 00 00 48 85 c0 74 24 48 85 d2 74 14 80 3a 00 74 18 48 8b 82 00 01 00 00 48 8d 84 02 08 01 00 00 <80> 38 00 74 04 48 89 07 c3 31 c0 c3 0f 1f 44 00 00 41 54 4c 8b 25
 [...]
 Call Trace:
  efi_mokvar_sysfs_init
  ? efi_mokvar_table_init
  do_one_initcall
  ? __kmalloc
  kernel_init_freeable
  ? rest_init
  kernel_init
  ret_from_fork
 Modules linked in:
 ---[ end trace 0de27ecc25d41b73 ]---

Expand the __ioremap_check_other() function to additionally check for this
other type of "runtime" data and indicate that it should be mapped encrypted
for an SEV guest.

Fixes: 58c909022a5a ("efi: Support for MOK variable config table")
Reported-by: Joerg Roedel <jroedel@...e.de>
Tested-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/mm/ioremap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 12c686c65ea9..60ade7dd71bd 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -118,7 +118,9 @@ static void __ioremap_check_other(resource_size_t addr, struct ioremap_desc *des
 	if (!IS_ENABLED(CONFIG_EFI))
 		return;
 
-	if (efi_mem_type(addr) == EFI_RUNTIME_SERVICES_DATA)
+	if (efi_mem_type(addr) == EFI_RUNTIME_SERVICES_DATA ||
+	    (efi_mem_type(addr) == EFI_BOOT_SERVICES_DATA &&
+	     efi_mem_attributes(addr) & EFI_MEMORY_RUNTIME))
 		desc->flags |= IORES_MAP_ENCRYPTED;
 }
 
-- 
2.31.1