[PATCH v5 04/12] x86/tdx: Add protected guest support for TDX guest

Kuppuswamy Sathyanarayanan
2021-08-04T18:14:55Z

TDX architecture provides a way for VM guests to be highly secure and
isolated (from untrusted VMM). To achieve this requirement, we can't
completely trust any data coming from VMM. TDX guest fixes this issue
by hardening the IO drivers against the attack from the VMM. Since we
have a requirement to modify the generic drivers, we need to use the
generic prot_guest_has() API to add TDX specific code in generic
drivers.

So add TDX guest support in prot_guest_has() API.

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---

Change since v4:
* Rebased on top of Tom Lendacky's protected guest changes.
* Moved memory encryption related protected guest flags in
tdx_prot_guest_has() to the patch that actually uses them.

arch/x86/Kconfig | 1 +
arch/x86/include/asm/protected_guest.h | 5 +++++
arch/x86/include/asm/tdx.h | 4 ++++
arch/x86/kernel/tdx.c | 13 +++++++++++++
include/linux/protected_guest.h | 3 +++
5 files changed, 26 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ab0e7c346c44..10f2cb51a39d 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -871,6 +871,7 @@ config INTEL_TDX_GUEST
depends on SECURITY
select X86_X2APIC
select SECURITY_LOCKDOWN_LSM
+ select ARCH_HAS_PROTECTED_GUEST
help
Provide support for running in a trusted domain on Intel processors
equipped with Trusted Domain eXtensions. TDX is a new Intel
diff --git a/arch/x86/include/asm/protected_guest.h b/arch/x86/include/asm/protected_guest.h
index b4a267dddf93..c67bf13c8ad3 100644
--- a/arch/x86/include/asm/protected_guest.h
+++ b/arch/x86/include/asm/protected_guest.h
@@ -12,12 +12,17 @@

#include <linux/mem_encrypt.h>

+#include <asm/processor.h>
+#include <asm/tdx.h>
+
#ifndef __ASSEMBLY__

static inline bool prot_guest_has(unsigned int attr)
{
if (sme_me_mask)
return amd_prot_guest_has(attr);
+ else if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
+ return tdx_prot_guest_has(attr);

return false;
}
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index c738bde944d1..eee226e4b3b4 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -11,10 +11,14 @@

void __init tdx_early_init(void);

+bool tdx_prot_guest_has(unsigned long flag);
+
#else

static inline void tdx_early_init(void) { };

+static inline bool tdx_prot_guest_has(unsigned long flag) { return false; }
+
#endif /* CONFIG_INTEL_TDX_GUEST */

#endif /* _ASM_X86_TDX_H */
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 39dd1515b131..1a032d700f51 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -4,6 +4,8 @@
#undef pr_fmt
#define pr_fmt(fmt) "x86/tdx: " fmt

+#include <linux/protected_guest.h>
+
#include <asm/tdx.h>

static inline bool cpuid_has_tdx_guest(void)
@@ -18,6 +20,17 @@ static inline bool cpuid_has_tdx_guest(void)
return !memcmp("IntelTDX ", sig, 12);
}

+bool tdx_prot_guest_has(unsigned long flag)
+{
+ switch (flag) {
+ case PATTR_GUEST_TDX:
+ return cpu_feature_enabled(X86_FEATURE_TDX_GUEST);
+ }
+
+ return false;
+}
+EXPORT_SYMBOL_GPL(tdx_prot_guest_has);
+
void __init tdx_early_init(void)
{
if (!cpuid_has_tdx_guest())
diff --git a/include/linux/protected_guest.h b/include/linux/protected_guest.h
index 7a7120abbb62..9085f5dd834c 100644
--- a/include/linux/protected_guest.h
+++ b/include/linux/protected_guest.h
@@ -22,6 +22,9 @@
#define PATTR_SEV 0x801
#define PATTR_SEV_ES 0x802

+/* 0x900 - 0x9ff reserved for Intel */
+#define PATTR_GUEST_TDX 0x900
+
#ifdef CONFIG_ARCH_HAS_PROTECTED_GUEST

#include <asm/protected_guest.h>
--
2.25.1