linux-kernel - [tip:efi/urgent] x86/efi: Access EFI MMIO data as unencrypted when SEV is active

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Message-ID: <tip-9b788f32bee6b0b293a4bdfca4ad4bb0206407fb@git.kernel.org>
Date:   Sun, 22 Jul 2018 08:19:02 -0700
From:   tip-bot for Brijesh Singh <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     tglx@...utronix.de, brijesh.singh@....com,
        ard.biesheuvel@...aro.org, mingo@...nel.org,
        linux-kernel@...r.kernel.org, thomas.lendacky@....com,
        hpa@...or.com, torvalds@...ux-foundation.org, peterz@...radead.org
Subject: [tip:efi/urgent] x86/efi: Access EFI MMIO data as unencrypted when
 SEV is active

Commit-ID:  9b788f32bee6b0b293a4bdfca4ad4bb0206407fb
Gitweb:     https://git.kernel.org/tip/9b788f32bee6b0b293a4bdfca4ad4bb0206407fb
Author:     Brijesh Singh <brijesh.singh@....com>
AuthorDate: Fri, 20 Jul 2018 10:28:46 +0900
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sun, 22 Jul 2018 14:10:38 +0200

x86/efi: Access EFI MMIO data as unencrypted when SEV is active

SEV guest fails to update the UEFI runtime variables stored in the
flash.

The following commit:

  1379edd59673 ("x86/efi: Access EFI data as encrypted when SEV is active")

unconditionally maps all the UEFI runtime data as 'encrypted' (C=1).

When SEV is active the UEFI runtime data marked as EFI_MEMORY_MAPPED_IO
should be mapped as 'unencrypted' so that both guest and hypervisor can
access the data.

Signed-off-by: Brijesh Singh <brijesh.singh@....com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
Cc: <stable@...r.kernel.org> # 4.15.x
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: linux-efi@...r.kernel.org
Fixes: 1379edd59673 ("x86/efi: Access EFI data as encrypted ...")
Link: http://lkml.kernel.org/r/20180720012846.23560-2-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/platform/efi/efi_64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 77873ce700ae..5f2eb3231607 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -417,7 +417,7 @@ static void __init __map_region(efi_memory_desc_t *md, u64 va)
 	if (!(md->attribute & EFI_MEMORY_WB))
 		flags |= _PAGE_PCD;
 
-	if (sev_active())
+	if (sev_active() && md->type != EFI_MEMORY_MAPPED_IO)
 		flags |= _PAGE_ENC;
 
 	pfn = md->phys_addr >> PAGE_SHIFT;