linux-kernel - Re: [PATCH] x86/ioremap: Map EFI runtime services data as encrypted for SEV

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Message-ID: <20200310174712.GG29372@zn.tnic>
Date:   Tue, 10 Mar 2020 18:47:31 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Bruce Rogers <brogers@...e.com>
Subject: Re: [PATCH] x86/ioremap: Map EFI runtime services data as encrypted
 for SEV

On Tue, Mar 10, 2020 at 05:37:38PM +0100, Borislav Petkov wrote:
> Let's wrap this in a new function which is called at the end of
> __ioremap_check_mem() instead of trying to map EFI_RUNTIME_SERVICES_DATA
> to IORES_DESC types and match the flags just so that we can preserve the
> flow. And add a comment above it why we're doing this.
> 
> As you said on IRC, none of the IO resource ranges covers the
> EFI_RUNTIME_SERVICES_DATA.

Ok, here's what I have. @joro, I know it is trivially different from the
version you tested but I'd appreciate it if you ran it again, just to be
sure.

Thx.

---
>From 244b62ca142c6296361bde953488fc64db31f1bd Mon Sep 17 00:00:00 2001
From: Tom Lendacky <thomas.lendacky@....com>
Date: Tue, 10 Mar 2020 18:35:57 +0100
Subject: [PATCH] x86/ioremap: Map EFI runtime services data as encrypted for
 SEV

The dmidecode program fails to properly decode the SMBIOS data supplied
by OVMF/UEFI when running in an SEV guest. The SMBIOS area, under SEV, is
encrypted and resides in reserved memory that is marked as EFI runtime
services data.

As a result, when memremap() is attempted for the SMBIOS data, it
can't be mapped as regular RAM (through try_ram_remap()) and, since
the address isn't part of the iomem resources list, it isn't mapped
encrypted through the fallback ioremap().

Add a new __ioremap_check_other() to deal with memory types like
EFI_RUNTIME_SERVICES_DATA which are not covered by the resource ranges.

This allows any runtime services data, which has been created encrypted,
to be mapped encrypted.

 [ bp: Move functionality to a separate function. ]

Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: <stable@...r.kernel.org> # 5.3
Link: https://lkml.kernel.org/r/2d9e16eb5b53dc82665c95c6764b7407719df7a0.1582645327.git.thomas.lendacky@amd.com
---
 arch/x86/mm/ioremap.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 44e4beb4239f..935a91e1fd77 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -106,6 +106,19 @@ static unsigned int __ioremap_check_encrypted(struct resource *res)
 	return 0;
 }
 
+/*
+ * The EFI runtime services data area is not covered by walk_mem_res(), but must
+ * be mapped encrypted when SEV is active.
+ */
+static void __ioremap_check_other(resource_size_t addr, struct ioremap_desc *desc)
+{
+	if (!sev_active())
+		return;
+
+	if (efi_mem_type(addr) == EFI_RUNTIME_SERVICES_DATA)
+		desc->flags |= IORES_MAP_ENCRYPTED;
+}
+
 static int __ioremap_collect_map_flags(struct resource *res, void *arg)
 {
 	struct ioremap_desc *desc = arg;
@@ -124,6 +137,9 @@ static int __ioremap_collect_map_flags(struct resource *res, void *arg)
  * To avoid multiple resource walks, this function walks resources marked as
  * IORESOURCE_MEM and IORESOURCE_BUSY and looking for system RAM and/or a
  * resource described not as IORES_DESC_NONE (e.g. IORES_DESC_ACPI_TABLES).
+ *
+ * After that, deal with misc other ranges in __ioremap_check_other() which do
+ * not fall into the above category.
  */
 static void __ioremap_check_mem(resource_size_t addr, unsigned long size,
 				struct ioremap_desc *desc)
@@ -135,6 +151,8 @@ static void __ioremap_check_mem(resource_size_t addr, unsigned long size,
 	memset(desc, 0, sizeof(struct ioremap_desc));
 
 	walk_mem_res(start, end, desc, __ioremap_collect_map_flags);
+
+	__ioremap_check_other(addr, desc);
 }
 
 /*
-- 
2.21.0

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette