[PATCH v7 13/22] x86/sev: Move __sev_[get|put]_ghcb() into separate noinstr object

[Ard Biesheuvel <ardb+git@google.com>]

From: Ard Biesheuvel <ardb@kernel.org>

Rename sev-nmi.c to noinstr.c, and move the get/put GHCB routines
into it too, which are also annotated as 'noinstr' and suffer from the
same problem as the NMI code, i.e., that GCC may ignore the
__no_sanitize_address__ function attribute implied by 'noinstr' and
insert KASAN instrumentation anyway.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/boot/startup/sev-startup.c        | 74 --------------------
 arch/x86/coco/sev/Makefile                 |  8 +--
 arch/x86/coco/sev/{sev-nmi.c => noinstr.c} | 74 ++++++++++++++++++++
 3 files changed, 78 insertions(+), 78 deletions(-)

diff --git a/arch/x86/boot/startup/sev-startup.c b/arch/x86/boot/startup/sev-startup.c
index 138b26f14ff1..9f4b4ca7deaa 100644
--- a/arch/x86/boot/startup/sev-startup.c
+++ b/arch/x86/boot/startup/sev-startup.c
@@ -41,83 +41,9 @@
 #include <asm/cpuid/api.h>
 #include <asm/cmdline.h>
 
-/*
- * Nothing shall interrupt this code path while holding the per-CPU
- * GHCB. The backup GHCB is only for NMIs interrupting this path.
- *
- * Callers must disable local interrupts around it.
- */
-noinstr struct ghcb *__sev_get_ghcb(struct ghcb_state *state)
-{
-	struct sev_es_runtime_data *data;
-	struct ghcb *ghcb;
-
-	WARN_ON(!irqs_disabled());
-
-	data = this_cpu_read(runtime_data);
-	ghcb = &data->ghcb_page;
-
-	if (unlikely(data->ghcb_active)) {
-		/* GHCB is already in use - save its contents */
-
-		if (unlikely(data->backup_ghcb_active)) {
-			/*
-			 * Backup-GHCB is also already in use. There is no way
-			 * to continue here so just kill the machine. To make
-			 * panic() work, mark GHCBs inactive so that messages
-			 * can be printed out.
-			 */
-			data->ghcb_active        = false;
-			data->backup_ghcb_active = false;
-
-			instrumentation_begin();
-			panic("Unable to handle #VC exception! GHCB and Backup GHCB are already in use");
-			instrumentation_end();
-		}
-
-		/* Mark backup_ghcb active before writing to it */
-		data->backup_ghcb_active = true;
-
-		state->ghcb = &data->backup_ghcb;
-
-		/* Backup GHCB content */
-		*state->ghcb = *ghcb;
-	} else {
-		state->ghcb = NULL;
-		data->ghcb_active = true;
-	}
-
-	return ghcb;
-}
-
 /* Include code shared with pre-decompression boot stage */
 #include "sev-shared.c"
 
-noinstr void __sev_put_ghcb(struct ghcb_state *state)
-{
-	struct sev_es_runtime_data *data;
-	struct ghcb *ghcb;
-
-	WARN_ON(!irqs_disabled());
-
-	data = this_cpu_read(runtime_data);
-	ghcb = &data->ghcb_page;
-
-	if (state->ghcb) {
-		/* Restore GHCB from Backup */
-		*ghcb = *state->ghcb;
-		data->backup_ghcb_active = false;
-		state->ghcb = NULL;
-	} else {
-		/*
-		 * Invalidate the GHCB so a VMGEXIT instruction issued
-		 * from userspace won't appear to be valid.
-		 */
-		vc_ghcb_invalidate(ghcb);
-		data->ghcb_active = false;
-	}
-}
-
 void __head
 early_set_pages_state(unsigned long vaddr, unsigned long paddr,
 		      unsigned long npages, const struct psc_desc *desc)
diff --git a/arch/x86/coco/sev/Makefile b/arch/x86/coco/sev/Makefile
index 342d79f0ab6a..3b8ae214a6a6 100644
--- a/arch/x86/coco/sev/Makefile
+++ b/arch/x86/coco/sev/Makefile
@@ -1,10 +1,10 @@
 # SPDX-License-Identifier: GPL-2.0
 
-obj-y += core.o sev-nmi.o vc-handle.o
+obj-y += core.o noinstr.o vc-handle.o
 
 # Clang 14 and older may fail to respect __no_sanitize_undefined when inlining
-UBSAN_SANITIZE_sev-nmi.o	:= n
+UBSAN_SANITIZE_noinstr.o	:= n
 
 # GCC may fail to respect __no_sanitize_address or __no_kcsan when inlining
-KASAN_SANITIZE_sev-nmi.o	:= n
-KCSAN_SANITIZE_sev-nmi.o	:= n
+KASAN_SANITIZE_noinstr.o	:= n
+KCSAN_SANITIZE_noinstr.o	:= n
diff --git a/arch/x86/coco/sev/sev-nmi.c b/arch/x86/coco/sev/noinstr.c
similarity index 61%
rename from arch/x86/coco/sev/sev-nmi.c
rename to arch/x86/coco/sev/noinstr.c
index d8dfaddfb367..b527eafb6312 100644
--- a/arch/x86/coco/sev/sev-nmi.c
+++ b/arch/x86/coco/sev/noinstr.c
@@ -106,3 +106,77 @@ void noinstr __sev_es_nmi_complete(void)
 
 	__sev_put_ghcb(&state);
 }
+
+/*
+ * Nothing shall interrupt this code path while holding the per-CPU
+ * GHCB. The backup GHCB is only for NMIs interrupting this path.
+ *
+ * Callers must disable local interrupts around it.
+ */
+noinstr struct ghcb *__sev_get_ghcb(struct ghcb_state *state)
+{
+	struct sev_es_runtime_data *data;
+	struct ghcb *ghcb;
+
+	WARN_ON(!irqs_disabled());
+
+	data = this_cpu_read(runtime_data);
+	ghcb = &data->ghcb_page;
+
+	if (unlikely(data->ghcb_active)) {
+		/* GHCB is already in use - save its contents */
+
+		if (unlikely(data->backup_ghcb_active)) {
+			/*
+			 * Backup-GHCB is also already in use. There is no way
+			 * to continue here so just kill the machine. To make
+			 * panic() work, mark GHCBs inactive so that messages
+			 * can be printed out.
+			 */
+			data->ghcb_active        = false;
+			data->backup_ghcb_active = false;
+
+			instrumentation_begin();
+			panic("Unable to handle #VC exception! GHCB and Backup GHCB are already in use");
+			instrumentation_end();
+		}
+
+		/* Mark backup_ghcb active before writing to it */
+		data->backup_ghcb_active = true;
+
+		state->ghcb = &data->backup_ghcb;
+
+		/* Backup GHCB content */
+		*state->ghcb = *ghcb;
+	} else {
+		state->ghcb = NULL;
+		data->ghcb_active = true;
+	}
+
+	return ghcb;
+}
+
+noinstr void __sev_put_ghcb(struct ghcb_state *state)
+{
+	struct sev_es_runtime_data *data;
+	struct ghcb *ghcb;
+
+	WARN_ON(!irqs_disabled());
+
+	data = this_cpu_read(runtime_data);
+	ghcb = &data->ghcb_page;
+
+	if (state->ghcb) {
+		/* Restore GHCB from Backup */
+		*ghcb = *state->ghcb;
+		data->backup_ghcb_active = false;
+		state->ghcb = NULL;
+	} else {
+		/*
+		 * Invalidate the GHCB so a VMGEXIT instruction issued
+		 * from userspace won't appear to be valid.
+		 */
+		vc_ghcb_invalidate(ghcb);
+		data->ghcb_active = false;
+	}
+}
-- 
2.51.0.268.g9569e192d0-goog