[PATCH v4 75/75] x86/sev-es: Check required CPU features for SEV-ES

Joerg Roedel
2020-07-14T12:11:38Z

From: Martin Radev <martin.b.radev@gmail.com>

Make sure the machine supports RDRAND, otherwise there is no trusted
source of of randomness in the system.

Signed-off-by: Martin Radev <martin.b.radev@gmail.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/boot/compressed/sev-es.c | 3 +++
arch/x86/kernel/sev-es-shared.c | 15 +++++++++++++++
arch/x86/kernel/sev-es.c | 3 +++
3 files changed, 21 insertions(+)

diff --git a/arch/x86/boot/compressed/sev-es.c b/arch/x86/boot/compressed/sev-es.c
index b522c18c0588..eb1a8b5cc753 100644
--- a/arch/x86/boot/compressed/sev-es.c
+++ b/arch/x86/boot/compressed/sev-es.c
@@ -145,6 +145,9 @@ void sev_es_shutdown_ghcb(void)
if (!boot_ghcb)
return;

+ if (!sev_es_check_cpu_features())
+ error("SEV-ES CPU Features missing.");
+
/*
* GHCB Page must be flushed from the cache and mapped encrypted again.
* Otherwise the running kernel will see strange cache effects when
diff --git a/arch/x86/kernel/sev-es-shared.c b/arch/x86/kernel/sev-es-shared.c
index 608f76d0d088..56de70cb80d8 100644
--- a/arch/x86/kernel/sev-es-shared.c
+++ b/arch/x86/kernel/sev-es-shared.c
@@ -9,6 +9,21 @@
* and is included directly into both code-bases.
*/

+#ifndef __BOOT_COMPRESSED
+#define error(v) pr_err(v)
+#define has_cpuflag(f) boot_cpu_has(f)
+#endif
+
+static bool __init sev_es_check_cpu_features(void)
+{
+ if (!has_cpuflag(X86_FEATURE_RDRAND)) {
+ error("RDRAND instruction not supported - no trusted source of randomness available\n");
+ return false;
+ }
+
+ return true;
+}
+
static void sev_es_terminate(unsigned int reason)
{
u64 val = GHCB_SEV_TERMINATE;
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 61308f9c8138..481ea00c58b6 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -682,6 +682,9 @@ void __init sev_es_init_vc_handling(void)
if (!sev_es_active())
return;

+ if (!sev_es_check_cpu_features())
+ panic("SEV-ES CPU Features missing");
+
/* Initialize per-cpu GHCB pages */
for_each_possible_cpu(cpu) {
sev_es_alloc_runtime_data(cpu);
--
2.27.0