linux-kernel - [PATCH 04/12] x86/sev: Do not hardcode GHCB protocol version

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Date:   Wed, 21 Jul 2021 16:20:07 +0200
From:   Joerg Roedel <joro@...tes.org>
To:     x86@...nel.org, Eric Biederman <ebiederm@...ssion.com>
Cc:     kexec@...ts.infradead.org, Joerg Roedel <jroedel@...e.de>,
        hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Martin Radev <martin.b.radev@...il.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Joerg Roedel <joro@...tes.org>, linux-coco@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH 04/12] x86/sev: Do not hardcode GHCB protocol version

From: Joerg Roedel <jroedel@...e.de>

Introduce the sev_get_ghcb_proto_ver() which will return the negotiated
GHCB protocol version and use it to set the version field in the GHCB.

Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 arch/x86/boot/compressed/sev.c | 5 +++++
 arch/x86/kernel/sev-shared.c   | 5 ++++-
 arch/x86/kernel/sev.c          | 5 +++++
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 1a2e49730f8b..101e08c67296 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -119,6 +119,11 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
 /* Include code for early handlers */
 #include "../../kernel/sev-shared.c"
 
+static u64 sev_get_ghcb_proto_ver(void)
+{
+	return GHCB_PROTOCOL_MAX;
+}
+
 static bool early_setup_sev_es(void)
 {
 	if (!sev_es_negotiate_protocol(NULL))
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 73eeb5897d16..36eaac2773ed 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -28,6 +28,9 @@ struct sev_ghcb_protocol_info {
 	unsigned int vm_proto;
 };
 
+/* Returns the negotiated GHCB Protocol version */
+static u64 sev_get_ghcb_proto_ver(void);
+
 static bool __init sev_es_check_cpu_features(void)
 {
 	if (!has_cpuflag(X86_FEATURE_RDRAND)) {
@@ -122,7 +125,7 @@ static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb,
 	enum es_result ret;
 
 	/* Fill in protocol and format specifiers */
-	ghcb->protocol_version = GHCB_PROTOCOL_MAX;
+	ghcb->protocol_version = sev_get_ghcb_proto_ver();
 	ghcb->ghcb_usage       = GHCB_DEFAULT_USAGE;
 
 	ghcb_set_sw_exit_code(ghcb, exit_code);
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 8084bfd7cce1..5d3422e8b25e 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -498,6 +498,11 @@ static enum es_result vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt
 /* Negotiated GHCB protocol version */
 static struct sev_ghcb_protocol_info ghcb_protocol_info __ro_after_init;
 
+static u64 sev_get_ghcb_proto_ver(void)
+{
+	return ghcb_protocol_info.vm_proto;
+}
+
 static noinstr void __sev_put_ghcb(struct ghcb_state *state)
 {
 	struct sev_es_runtime_data *data;
-- 
2.31.1