[RFC PATCH 04/12] x86/sev: Do not hardcode GHCB protocol version

From: Joerg Roedel <joro@8bytes.org>
To: x86@kernel.org
Cc: Joerg Roedel <joro@8bytes.org>, Joerg Roedel <jroedel@suse.de>,
	hpa@zytor.com, Andy Lutomirski <luto@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Jiri Slaby <jslaby@suse.cz>,
	Dan Williams <dan.j.williams@intel.com>,
	Tom Lendacky <thomas.lendacky@amd.com>,
	Juergen Gross <jgross@suse.com>,
	Kees Cook <keescook@chromium.org>,
	David Rientjes <rientjes@google.com>,
	Cfir Cohen <cfir@google.com>, Erdem Aktas <erdemaktas@google.com>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mike Stunes <mstunes@vmware.com>,
	Sean Christopherson <seanjc@google.com>,
	Martin Radev <martin.b.radev@gmail.com>,
	Arvind Sankar <nivedita@alum.mit.edu>,
	linux-coco@lists.linux.dev, linux-kernel@vger.kernel.org,
	kvm@vger.kernel.org, virtualization@lists.linux-foundation.org
Subject: [RFC PATCH 04/12] x86/sev: Do not hardcode GHCB protocol version
Date: Mon,  5 Jul 2021 10:24:35 +0200	[thread overview]
Message-ID: <20210705082443.14721-5-joro@8bytes.org> (raw)
In-Reply-To: <20210705082443.14721-1-joro@8bytes.org>

From: Joerg Roedel <jroedel@suse.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@suse.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

