Subject: [PATCH] x86/sev-es: Expose __sev_es_ghcb_hv_call() to call ghcb hv call out of sev code

From: Tianyu Lan <[email-masked]>
Date: Wed, 20 Oct 2021 02:23:16 -0400

From: Tianyu Lan <[email-masked]>

Hyper-V also needs to call ghcb hv call to write/read MSR in Isolation VM.
So expose __sev_es_ghcb_hv_call() to call it in the Hyper-V code.

Signed-off-by: Tianyu Lan <[email-masked]>
---
 arch/x86/include/asm/sev.h   | 11 +++++++++++
 arch/x86/kernel/sev-shared.c | 24 +++++++++++++++++++-----
 2 files changed, 30 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index fa5cd05d3b5b..295c847c3cd4 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -81,12 +81,23 @@ static __always_inline void sev_es_nmi_complete(void)
 		__sev_es_nmi_complete();
 }
 extern int __init sev_es_efi_map_ghcbs(pgd_t *pgd);
+extern enum es_result __sev_es_ghcb_hv_call(struct ghcb *ghcb,
+					    struct es_em_ctxt *ctxt,
+					    u64 exit_code, u64 exit_info_1,
+					    u64 exit_info_2);
 #else
 static inline void sev_es_ist_enter(struct pt_regs *regs) { }
 static inline void sev_es_ist_exit(void) { }
 static inline int sev_es_setup_ap_jump_table(struct real_mode_header *rmh) { return 0; }
 static inline void sev_es_nmi_complete(void) { }
 static inline int sev_es_efi_map_ghcbs(pgd_t *pgd) { return 0; }
+static inline enum es_result
+__sev_es_ghcb_hv_call(struct ghcb *ghcb,
+		      u64 exit_code, u64 exit_info_1,
+		      u64 exit_info_2)
+{
+	return ES_VMM_ERROR;
+}
 #endif
 
 #endif
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index ea9abd69237e..08c97cb057fa 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -124,10 +124,14 @@ static enum es_result verify_exception_info(struct ghcb *ghcb, struct es_em_ctxt
 	return ES_VMM_ERROR;
 }
 
-static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
-					  struct es_em_ctxt *ctxt,
-					  u64 exit_code, u64 exit_info_1,
-					  u64 exit_info_2)
+/*
+ * __sev_es_ghcb_hv_call() is also used in the other platform code(e.g
+ * Hyper-V).
+ */
+enum es_result __sev_es_ghcb_hv_call(struct ghcb *ghcb,
+				     struct es_em_ctxt *ctxt,
+				     u64 exit_code, u64 exit_info_1,
+				     u64 exit_info_2)
 {
 	/* Fill in protocol and format specifiers */
 	ghcb->protocol_version = GHCB_PROTOCOL_MAX;
@@ -137,12 +141,22 @@ static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
 	ghcb_set_sw_exit_info_1(ghcb, exit_info_1);
 	ghcb_set_sw_exit_info_2(ghcb, exit_info_2);
 
-	sev_es_wr_ghcb_msr(__pa(ghcb));
 	VMGEXIT();
 
 	return verify_exception_info(ghcb, ctxt);
 }
 
+static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
+					  struct es_em_ctxt *ctxt,
+					  u64 exit_code, u64 exit_info_1,
+					  u64 exit_info_2)
+{
+	sev_es_wr_ghcb_msr(__pa(ghcb));
+
+	return __sev_es_ghcb_hv_call(ghcb, ctxt, exit_code, exit_info_1,
+				     exit_info_2);
+}
+
 /*
  * Boot VC Handler - This is the first VC handler during boot, there is no GHCB
  * page yet, so it only supports the MSR based communication with the
-- 
2.25.1