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

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Date:   Tue,  3 Jul 2018 08:32:00 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     x86@...nel.org, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...e.de>, kvm@...r.kernel.org,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Andy Lutomirski <luto@...nel.org>,
        "# 4 . 15 . x" <stable@...r.kernel.org>
Subject: [PATCH] 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. 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.

Fixes: 1379edd59673 (x86/efi: Access EFI data as encrypted ...)
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Borislav Petkov <bp@...e.de>
Cc: linux-efi@...r.kernel.org
Cc: kvm@...r.kernel.org
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Matt Fleming <matt@...eblueprint.co.uk>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: <stable@...r.kernel.org> # 4.15.x
Signed-off-by: Brijesh Singh <brijesh.singh@....com>
---
 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 77873ce..5f2eb32 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;
-- 
2.7.4