diff mbox series

[2/2] x86/sev: Get rid of special sev_es_enable_key

Message ID 20230318115634.9392-3-bp@alien8.de
State New
Headers
Series SECC-ES: Cleanups |

Commit Message

Borislav Petkov March 18, 2023, 11:56 a.m. UTC 
  From: "Borislav Petkov (AMD)" <bp@alien8.de>

A SEV-ES guest is active on AMD when CC_ATTR_GUEST_STATE_ENCRYPT is set.
I.e., MSR_AMD64_SEV, bit 1, SEV_ES_Enabled. So no need for a special
static key.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
---
 arch/x86/coco/core.c       |  2 +-
 arch/x86/include/asm/sev.h | 11 +++++++----
 arch/x86/kernel/sev.c      |  5 -----
 3 files changed, 8 insertions(+), 10 deletions(-)

Comments

Thomas Gleixner March 23, 2023, 9:17 a.m. UTC | #1 
On Sat, Mar 18 2023 at 12:56, Borislav Petkov wrote:
> -bool cc_platform_has(enum cc_attr attr)
> +bool noinstr cc_platform_has(enum cc_attr attr)

That's not sufficient. This function invokes static functions which the
compiler can rightfully put out of line resulting in a noinstr violation.

Thanks,

        tglx
Borislav Petkov March 23, 2023, 9:53 a.m. UTC | #2 
On Thu, Mar 23, 2023 at 10:17:15AM +0100, Thomas Gleixner wrote:
> That's not sufficient. This function invokes static functions which the
> compiler can rightfully put out of line resulting in a noinstr violation.

Right, as mentioned on IRC, if we're going to use the cc_platform_has()
thing to do simple arch-agnostic confidential guests checks, perhaps we
should make it and the underlying functions it calls simply
__always_inline so that the compiler can optimize stuff even more and
not have function calls for such simple tests...
diff mbox series

Patch

diff --git a/arch/x86/coco/core.c b/arch/x86/coco/core.c
index 684f0a910475..17f2b690a485 100644
--- a/arch/x86/coco/core.c
+++ b/arch/x86/coco/core.c
@@ -81,7 +81,7 @@  static bool hyperv_cc_platform_has(enum cc_attr attr)
 	return attr == CC_ATTR_GUEST_MEM_ENCRYPT;
 }
 
-bool cc_platform_has(enum cc_attr attr)
+bool noinstr cc_platform_has(enum cc_attr attr)
 {
 	switch (cc_vendor) {
 	case CC_VENDOR_AMD:
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index ebc271bb6d8e..1335781e4976 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -12,6 +12,7 @@ 
 #include <asm/insn.h>
 #include <asm/sev-common.h>
 #include <asm/bootparam.h>
+#include <asm/coco.h>
 
 #define GHCB_PROTOCOL_MIN	1ULL
 #define GHCB_PROTOCOL_MAX	2ULL
@@ -134,24 +135,26 @@  struct snp_secrets_page_layout {
 } __packed;
 
 #ifdef CONFIG_AMD_MEM_ENCRYPT
-extern struct static_key_false sev_es_enable_key;
 extern void __sev_es_ist_enter(struct pt_regs *regs);
 extern void __sev_es_ist_exit(void);
 static __always_inline void sev_es_ist_enter(struct pt_regs *regs)
 {
-	if (static_branch_unlikely(&sev_es_enable_key))
+	if (cc_vendor == CC_VENDOR_AMD &&
+	    cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
 		__sev_es_ist_enter(regs);
 }
 static __always_inline void sev_es_ist_exit(void)
 {
-	if (static_branch_unlikely(&sev_es_enable_key))
+	if (cc_vendor == CC_VENDOR_AMD &&
+	    cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
 		__sev_es_ist_exit();
 }
 extern int sev_es_setup_ap_jump_table(struct real_mode_header *rmh);
 extern void __sev_es_nmi_complete(void);
 static __always_inline void sev_es_nmi_complete(void)
 {
-	if (static_branch_unlikely(&sev_es_enable_key))
+	if (cc_vendor == CC_VENDOR_AMD &&
+	    cc_platform_has(CC_ATTR_GUEST_STATE_ENCRYPT))
 		__sev_es_nmi_complete();
 }
 extern int __init sev_es_efi_map_ghcbs(pgd_t *pgd);
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 679026a640ef..4fdba49b6e38 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -111,8 +111,6 @@  struct ghcb_state {
 };
 
 static DEFINE_PER_CPU(struct sev_es_runtime_data*, runtime_data);
-DEFINE_STATIC_KEY_FALSE(sev_es_enable_key);
-
 static DEFINE_PER_CPU(struct sev_es_save_area *, sev_vmsa);
 
 struct sev_config {
@@ -1393,9 +1391,6 @@  void __init sev_es_init_vc_handling(void)
 			sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);
 	}
 
-	/* Enable SEV-ES special handling */
-	static_branch_enable(&sev_es_enable_key);
-
 	/* Initialize per-cpu GHCB pages */
 	for_each_possible_cpu(cpu) {
 		alloc_runtime_data(cpu);