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Message-ID: <20220220150159.l6agp4yt2f3hk4fw@black.fi.intel.com>
Date: Sun, 20 Feb 2022 18:01:59 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
luto@...nel.org, peterz@...radead.org,
sathyanarayanan.kuppuswamy@...ux.intel.com, aarcange@...hat.com,
ak@...ux.intel.com, dan.j.williams@...el.com, david@...hat.com,
hpa@...or.com, jgross@...e.com, jmattson@...gle.com,
joro@...tes.org, jpoimboe@...hat.com, knsathya@...nel.org,
pbonzini@...hat.com, sdeep@...are.com, seanjc@...gle.com,
tony.luck@...el.com, vkuznets@...hat.com, wanpengli@...cent.com,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv3 03/32] x86/tdx: Detect running as a TDX guest in early
boot
On Fri, Feb 18, 2022 at 01:07:11PM -0800, Dave Hansen wrote:
> > Since cc_plaform_has() API will be used frequently across the boot
> > code, instead of repeatedly detecting the TDX guest status using the
> > CPUID instruction, detect once and cache the result.
>
> Isn't this a remnant of an old implementation where there was a separate
> 'tdx_enabled' variable in addition to X86_FEATURE_TDX_GUEST?
>
> Does this "caching" refer to X86_FEATURE_TDX_GUEST or the old thing?
Yeah, sorry. I failed to update commit message properly.
Updated patch is below.
>From 0e824103625186b5001bae2c8f5767bfc7deb626 Mon Sep 17 00:00:00 2001
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
Date: Fri, 8 Oct 2021 16:03:03 -0700
Subject: [PATCH] x86/tdx: Detect running as a TDX guest in early boot
In preparation of extending cc_platform_has() API to support TDX guest,
use CPUID instruction to detect support for TDX guests in the early
boot code (via tdx_early_init()). Since copy_bootdata() is the first
user of cc_platform_has() API, detect the TDX guest status before it.
Define a synthetic feature flag (X86_FEATURE_TDX_GUEST) and set this
bit in a valid TDX guest platform.
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
Reviewed-by: Tony Luck <tony.luck@...el.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
arch/x86/Kbuild | 1 +
arch/x86/Kconfig | 12 ++++++++++++
arch/x86/coco/Makefile | 2 ++
arch/x86/coco/tdx.c | 22 ++++++++++++++++++++++
arch/x86/include/asm/cpufeatures.h | 1 +
arch/x86/include/asm/disabled-features.h | 8 +++++++-
arch/x86/include/asm/tdx.h | 21 +++++++++++++++++++++
arch/x86/kernel/head64.c | 4 ++++
8 files changed, 70 insertions(+), 1 deletion(-)
create mode 100644 arch/x86/coco/Makefile
create mode 100644 arch/x86/coco/tdx.c
create mode 100644 arch/x86/include/asm/tdx.h
diff --git a/arch/x86/Kbuild b/arch/x86/Kbuild
index f384cb1a4f7a..b4861abb4386 100644
--- a/arch/x86/Kbuild
+++ b/arch/x86/Kbuild
@@ -1,4 +1,5 @@
# SPDX-License-Identifier: GPL-2.0
+obj-y += coco/
obj-y += entry/
obj-$(CONFIG_PERF_EVENTS) += events/
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 391c4cac8958..8dc575f3aba1 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -880,6 +880,18 @@ config ACRN_GUEST
IOT with small footprint and real-time features. More details can be
found in https://projectacrn.org/.
+config INTEL_TDX_GUEST
+ bool "Intel TDX (Trust Domain Extensions) - Guest Support"
+ depends on X86_64 && CPU_SUP_INTEL
+ depends on X86_X2APIC
+ help
+ Support running as a guest under Intel TDX. Without this support,
+ the guest kernel can not boot or run under TDX.
+ TDX includes memory encryption and integrity capabilities
+ which protect the confidentiality and integrity of guest
+ memory contents and CPU state. TDX guests are protected from
+ some attacks from the VMM.
+
endif #HYPERVISOR_GUEST
source "arch/x86/Kconfig.cpu"
diff --git a/arch/x86/coco/Makefile b/arch/x86/coco/Makefile
new file mode 100644
index 000000000000..b285d485a72e
--- /dev/null
+++ b/arch/x86/coco/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_INTEL_TDX_GUEST) += tdx.o
diff --git a/arch/x86/coco/tdx.c b/arch/x86/coco/tdx.c
new file mode 100644
index 000000000000..77c26c6b932d
--- /dev/null
+++ b/arch/x86/coco/tdx.c
@@ -0,0 +1,22 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2021-2022 Intel Corporation */
+
+#undef pr_fmt
+#define pr_fmt(fmt) "tdx: " fmt
+
+#include <linux/cpufeature.h>
+#include <asm/tdx.h>
+
+void __init tdx_early_init(void)
+{
+ u32 eax, sig[3];
+
+ cpuid_count(TDX_CPUID_LEAF_ID, 0, &eax, &sig[0], &sig[2], &sig[1]);
+
+ if (memcmp(TDX_IDENT, sig, 12))
+ return;
+
+ setup_force_cpu_cap(X86_FEATURE_TDX_GUEST);
+
+ pr_info("Guest detected\n");
+}
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index 5cd22090e53d..cacc8dde854b 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -238,6 +238,7 @@
#define X86_FEATURE_VMW_VMMCALL ( 8*32+19) /* "" VMware prefers VMMCALL hypercall instruction */
#define X86_FEATURE_PVUNLOCK ( 8*32+20) /* "" PV unlock function */
#define X86_FEATURE_VCPUPREEMPT ( 8*32+21) /* "" PV vcpu_is_preempted function */
+#define X86_FEATURE_TDX_GUEST ( 8*32+22) /* Intel Trust Domain Extensions Guest */
/* Intel-defined CPU features, CPUID level 0x00000007:0 (EBX), word 9 */
#define X86_FEATURE_FSGSBASE ( 9*32+ 0) /* RDFSBASE, WRFSBASE, RDGSBASE, WRGSBASE instructions*/
diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
index 1231d63f836d..b37de8268c9a 100644
--- a/arch/x86/include/asm/disabled-features.h
+++ b/arch/x86/include/asm/disabled-features.h
@@ -68,6 +68,12 @@
# define DISABLE_SGX (1 << (X86_FEATURE_SGX & 31))
#endif
+#ifdef CONFIG_INTEL_TDX_GUEST
+# define DISABLE_TDX_GUEST 0
+#else
+# define DISABLE_TDX_GUEST (1 << (X86_FEATURE_TDX_GUEST & 31))
+#endif
+
/*
* Make sure to add features to the correct mask
*/
@@ -79,7 +85,7 @@
#define DISABLED_MASK5 0
#define DISABLED_MASK6 0
#define DISABLED_MASK7 (DISABLE_PTI)
-#define DISABLED_MASK8 0
+#define DISABLED_MASK8 (DISABLE_TDX_GUEST)
#define DISABLED_MASK9 (DISABLE_SMAP|DISABLE_SGX)
#define DISABLED_MASK10 0
#define DISABLED_MASK11 0
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
new file mode 100644
index 000000000000..ba8042ce61c2
--- /dev/null
+++ b/arch/x86/include/asm/tdx.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2021-2022 Intel Corporation */
+#ifndef _ASM_X86_TDX_H
+#define _ASM_X86_TDX_H
+
+#include <linux/init.h>
+
+#define TDX_CPUID_LEAF_ID 0x21
+#define TDX_IDENT "IntelTDX "
+
+#ifdef CONFIG_INTEL_TDX_GUEST
+
+void __init tdx_early_init(void);
+
+#else
+
+static inline void tdx_early_init(void) { };
+
+#endif /* CONFIG_INTEL_TDX_GUEST */
+
+#endif /* _ASM_X86_TDX_H */
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 4f5ecbbaae77..6dff50c3edd6 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -40,6 +40,7 @@
#include <asm/extable.h>
#include <asm/trapnr.h>
#include <asm/sev.h>
+#include <asm/tdx.h>
/*
* Manage page tables very early on.
@@ -514,6 +515,9 @@ asmlinkage __visible void __init x86_64_start_kernel(char * real_mode_data)
idt_setup_early_handler();
+ /* Needed before cc_platform_has() can be used for TDX */
+ tdx_early_init();
+
copy_bootdata(__va(real_mode_data));
/*
--
Kirill A. Shutemov
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