cpu/x86/smm,lib/cbmem_console: Enable CBMEMC when using DEBUG_SMI

This change will allow the SMI handler to write to the cbmem console
buffer. Normally SMIs can only be debugged using some kind of serial
port (UART). By storing the SMI logs into cbmem we can debug SMIs using
`cbmem -1`. Now that these logs are available to the OS we could also
verify there were no errors in the SMI handler.

Since SMM can write to all of DRAM, we can't trust any pointers
provided by cbmem after the OS has booted. For this reason we store the
cbmem console pointer as part of the SMM runtime parameters. The cbmem
console is implemented as a circular buffer so it will never write
outside of this area.

BUG=b:221231786
TEST=Boot non-serial FW with DEBUG_SMI and verified SMI messages are
visible when running `cbmem -1`. Perform a suspend/resume cycle and
verify new SMI events are written to the cbmem console log.

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
Change-Id: Ia1e310a12ca2f54210ccfaee58807cb808cfff79
Reviewed-on: https://review.coreboot.org/c/coreboot/+/62355
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Karthik Ramasubramanian <kramasub@google.com>

2 files changed, 19 insertions, 0 deletions

diff --git a/src/cpu/x86/smm/smm_module_handler.c b/src/cpu/x86/smm/smm_module_handler.c
index cab691d974..bd4149a797 100644
--- a/src/cpu/x86/smm/smm_module_handler.c
+++ b/src/cpu/x86/smm/smm_module_handler.c
@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
 #include <arch/io.h>
+#include <console/cbmem_console.h>
 #include <console/console.h>
 #include <commonlib/region.h>
 #include <cpu/x86/smm.h>
@@ -48,6 +49,12 @@ static void smi_release_lock(void)
 	);
 }
 
+void smm_get_cbmemc_buffer(void **buffer_out, size_t *size_out)
+{
+	*buffer_out = smm_runtime.cbmemc;
+	*size_out = smm_runtime.cbmemc_size;
+}
+
 void io_trap_handler(int smif)
 {
 	/* If a handler function handled a given IO trap, it
diff --git a/src/cpu/x86/smm/smm_module_loader.c b/src/cpu/x86/smm/smm_module_loader.c
index 14e2aa3b74..17c6779122 100644
--- a/src/cpu/x86/smm/smm_module_loader.c
+++ b/src/cpu/x86/smm/smm_module_loader.c
@@ -5,6 +5,7 @@
 #include <stdint.h>
 #include <string.h>
 #include <rmodule.h>
+#include <cbmem.h>
 #include <cpu/x86/smm.h>
 #include <commonlib/helpers.h>
 #include <console/console.h>
@@ -479,6 +480,7 @@ int smm_load_module(const uintptr_t smram_base, const size_t smram_size,
 	void *fxsave_area;
 	size_t total_size = 0;
 	uintptr_t base; /* The base for the permanent handler */
+	const struct cbmem_entry *cbmemc;
 
 	if (CONFIG(SMM_ASEG))
 		return smm_load_module_aseg(smram_base, smram_size, params);
@@ -557,6 +559,14 @@ int smm_load_module(const uintptr_t smram_base, const size_t smram_size,
 	handler_mod_params->num_cpus = params->num_cpus;
 	handler_mod_params->gnvs_ptr = (uintptr_t)acpi_get_gnvs();
 
+	if (CONFIG(CONSOLE_CBMEM) && (cbmemc = cbmem_entry_find(CBMEM_ID_CONSOLE))) {
+		handler_mod_params->cbmemc = cbmem_entry_start(cbmemc);
+		handler_mod_params->cbmemc_size = cbmem_entry_size(cbmemc);
+	} else {
+		handler_mod_params->cbmemc = 0;
+		handler_mod_params->cbmemc_size = 0;
+	}
+
 	printk(BIOS_DEBUG, "%s: smram_start: 0x%lx\n",  __func__, smram_base);
 	printk(BIOS_DEBUG, "%s: smram_end: %lx\n", __func__, smram_base + smram_size);
 	printk(BIOS_DEBUG, "%s: handler start %p\n",
@@ -577,6 +587,8 @@ int smm_load_module(const uintptr_t smram_base, const size_t smram_size,
 	printk(BIOS_DEBUG, "%s: per_cpu_save_state_size = 0x%x\n", __func__,
 	       handler_mod_params->save_state_size);
 	printk(BIOS_DEBUG, "%s: num_cpus = 0x%x\n", __func__, handler_mod_params->num_cpus);
+	printk(BIOS_DEBUG, "%s: cbmemc = %p, cbmemc_size = %#x\n", __func__,
+	       handler_mod_params->cbmemc, handler_mod_params->cbmemc_size);
 	printk(BIOS_DEBUG, "%s: total_save_state_size = 0x%x\n", __func__,
 	       (handler_mod_params->save_state_size * handler_mod_params->num_cpus));