[PATCH v2 03/12] x86/sev: Save and print negotiated GHCB protocol version

Joerg Roedel
2021-09-13T15:56:31Z

From: Joerg Roedel <jroedel@suse.de>

Save the results of the GHCB protocol negotiation into a data structure
and print information about versions supported and used to the kernel
log.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
arch/x86/boot/compressed/sev.c | 2 +-
arch/x86/kernel/sev-shared.c | 22 +++++++++++++++++++++-
arch/x86/kernel/sev.c | 13 ++++++++++++-
3 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
index 670e998fe930..1a2e49730f8b 100644
--- a/arch/x86/boot/compressed/sev.c
+++ b/arch/x86/boot/compressed/sev.c
@@ -121,7 +121,7 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,

static bool early_setup_sev_es(void)
{
- if (!sev_es_negotiate_protocol())
+ if (!sev_es_negotiate_protocol(NULL))
sev_es_terminate(GHCB_SEV_ES_REASON_PROTOCOL_UNSUPPORTED);

if (set_page_decrypted((unsigned long)&boot_ghcb_page))
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 9f90f460a28c..73eeb5897d16 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -14,6 +14,20 @@
#define has_cpuflag(f) boot_cpu_has(f)
#endif

+/*
+ * struct sev_ghcb_protocol_info - Used to return GHCB protocol
+ * negotiation details.
+ *
+ * @hv_proto_min: Minimum GHCB protocol version supported by Hypervisor
+ * @hv_proto_max: Maximum GHCB protocol version supported by Hypervisor
+ * @vm_proto: Protocol version the VM (this kernel) will use
+ */
+struct sev_ghcb_protocol_info {
+ unsigned int hv_proto_min;
+ unsigned int hv_proto_max;
+ unsigned int vm_proto;
+};
+
static bool __init sev_es_check_cpu_features(void)
{
if (!has_cpuflag(X86_FEATURE_RDRAND)) {
@@ -42,7 +56,7 @@ static void __noreturn sev_es_terminate(unsigned int reason)
asm volatile("hlt\n" : : : "memory");
}

-static bool sev_es_negotiate_protocol(void)
+static bool sev_es_negotiate_protocol(struct sev_ghcb_protocol_info *info)
{
u64 val;

@@ -58,6 +72,12 @@ static bool sev_es_negotiate_protocol(void)
GHCB_MSR_PROTO_MIN(val) > GHCB_PROTO_OUR)
return false;

+ if (info) {
+ info->hv_proto_min = GHCB_MSR_PROTO_MIN(val);
+ info->hv_proto_max = GHCB_MSR_PROTO_MAX(val);
+ info->vm_proto = GHCB_PROTO_OUR;
+ }
+
return true;
}

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index a6895e440bc3..8084bfd7cce1 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -495,6 +495,9 @@ static enum es_result vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt
/* Include code shared with pre-decompression boot stage */
#include "sev-shared.c"

+/* Negotiated GHCB protocol version */
+static struct sev_ghcb_protocol_info ghcb_protocol_info __ro_after_init;
+
static noinstr void __sev_put_ghcb(struct ghcb_state *state)
{
struct sev_es_runtime_data *data;
@@ -665,7 +668,7 @@ static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
static bool __init sev_es_setup_ghcb(void)
{
/* First make sure the hypervisor talks a supported protocol. */
- if (!sev_es_negotiate_protocol())
+ if (!sev_es_negotiate_protocol(&ghcb_protocol_info))
return false;

/*
@@ -794,6 +797,14 @@ void __init sev_es_init_vc_handling(void)

/* Secondary CPUs use the runtime #VC handler */
initial_vc_handler = (unsigned long)kernel_exc_vmm_communication;
+
+ /*
+ * Print information about supported and negotiated GHCB protocol
+ * versions.
+ */
+ pr_info("Hypervisor GHCB protocol version support: min=%u max=%u\n",
+ ghcb_protocol_info.hv_proto_min, ghcb_protocol_info.hv_proto_max);
+ pr_info("Using GHCB protocol version %u\n", ghcb_protocol_info.vm_proto);
}

static void __init vc_early_forward_exception(struct es_em_ctxt *ctxt)
--
2.33.0