From: Ard Biesheuvel <ardb@kernel.org>
Date: Thu, 28 Aug 2025 10:22:05 +0000 (+0200)
Subject: x86/sev: Use MSR protocol for remapping SVSM calling area
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=c15a4705d59caeb44f4c373cf04e89041309e568;p=users%2Fhch%2Fmisc.git

x86/sev: Use MSR protocol for remapping SVSM calling area

As the preceding code comment already indicates, remapping the SVSM
calling area occurs long before the GHCB page is configured, and so
calling svsm_perform_call_protocol() is guaranteed to result in a call
to svsm_perform_msr_protocol().

So just call the latter directly. This allows most of the GHCB based API
infrastructure to be moved out of the startup code in a subsequent
patch.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Link: https://lore.kernel.org/20250828102202.1849035-26-ardb+git@google.com
---

diff --git a/arch/x86/boot/startup/sev-shared.c b/arch/x86/boot/startup/sev-shared.c
index ed88dfe7605e..975d2b02926a 100644
--- a/arch/x86/boot/startup/sev-shared.c
+++ b/arch/x86/boot/startup/sev-shared.c
@@ -724,6 +724,17 @@ static void __head setup_cpuid_table(const struct cc_blob_sev_info *cc_info)
 	}
 }
 
+static int __head svsm_call_msr_protocol(struct svsm_call *call)
+{
+	int ret;
+
+	do {
+		ret = svsm_perform_msr_protocol(call);
+	} while (ret == -EAGAIN);
+
+	return ret;
+}
+
 static void __head svsm_pval_4k_page(unsigned long paddr, bool validate)
 {
 	struct svsm_pvalidate_call *pc;
diff --git a/arch/x86/boot/startup/sev-startup.c b/arch/x86/boot/startup/sev-startup.c
index 0b7e3b950183..8412807a865c 100644
--- a/arch/x86/boot/startup/sev-startup.c
+++ b/arch/x86/boot/startup/sev-startup.c
@@ -295,7 +295,6 @@ found_cc_info:
 static __head void svsm_setup(struct cc_blob_sev_info *cc_info)
 {
 	struct svsm_call call = {};
-	int ret;
 	u64 pa;
 
 	/*
@@ -325,8 +324,8 @@ static __head void svsm_setup(struct cc_blob_sev_info *cc_info)
 	call.caa = svsm_get_caa();
 	call.rax = SVSM_CORE_CALL(SVSM_CORE_REMAP_CA);
 	call.rcx = pa;
-	ret = svsm_perform_call_protocol(&call);
-	if (ret)
+
+	if (svsm_call_msr_protocol(&call))
 		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_SVSM_CA_REMAP_FAIL);
 
 	boot_svsm_caa = (struct svsm_ca *)pa;