cpu/x86/smm: Refactor creating a stub/save state map
This code was very hard to read so rewrite it using as few mutable local
variables as possible.
Tested on qemu with 128 cores.
Change-Id: I7a455ba45a1c92533a8ecfd1aeecf34b4a63e409
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63474
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@tutanota.com>
diff --git a/src/cpu/x86/smm/smm_module_loader.c b/src/cpu/x86/smm/smm_module_loader.c
index 9068435..00c6cf9 100644
--- a/src/cpu/x86/smm/smm_module_loader.c
+++ b/src/cpu/x86/smm/smm_module_loader.c
@@ -1,5 +1,6 @@
/* SPDX-License-Identifier: GPL-2.0-only */
+#include "assert.h"
#include <acpi/acpi_gnvs.h>
#include <stddef.h>
#include <stdint.h>
@@ -85,65 +86,54 @@
* input : num_cpus in the system. The map will
* be created from 0 to num_cpus.
*/
-static int smm_create_map(uintptr_t smbase, unsigned int num_cpus,
- const struct smm_loader_params *params)
+static int smm_create_map(const uintptr_t smbase, const unsigned int num_cpus,
+ const struct smm_loader_params *params)
{
- unsigned int i;
struct rmodule smm_stub;
- unsigned int ss_size = params->per_cpu_save_state_size, stub_size;
- unsigned int smm_entry_offset = SMM_ENTRY_OFFSET;
- unsigned int seg_count = 0, segments = 0, available;
- unsigned int cpus_in_segment = 0;
- unsigned int base = smbase;
+
+ if (ARRAY_SIZE(cpus) < num_cpus) {
+ printk(BIOS_ERR, "%s: increase MAX_CPUS in Kconfig\n", __func__);
+ return 0;
+ }
if (rmodule_parse(&_binary_smmstub_start, &smm_stub)) {
printk(BIOS_ERR, "%s: unable to get SMM module size\n", __func__);
return 0;
}
- stub_size = rmodule_memory_size(&smm_stub);
- /* How many CPUs can fit into one 64K segment? */
- available = 0xFFFF - smm_entry_offset - ss_size - stub_size;
- if (available > 0) {
- cpus_in_segment = available / ss_size;
- /* minimum segments needed will always be 1 */
- segments = num_cpus / cpus_in_segment + 1;
- printk(BIOS_DEBUG,
- "%s: cpus allowed in one segment %d\n", __func__, cpus_in_segment);
- printk(BIOS_DEBUG,
- "%s: min # of segments needed %d\n", __func__, segments);
- } else {
- printk(BIOS_ERR, "%s: not enough space in SMM to setup all CPUs\n", __func__);
- printk(BIOS_ERR, " save state & stub size need to be reduced\n");
- printk(BIOS_ERR, " or increase SMRAM size\n");
+ /*
+ * How many CPUs can fit into one 64K segment?
+ * Make sure that the first stub does not overlap with the last save state of a segment.
+ */
+ const size_t stub_size = rmodule_memory_size(&smm_stub);
+ const size_t needed_ss_size = MAX(params->real_cpu_save_state_size, stub_size);
+ const size_t cpus_per_segment =
+ (SMM_CODE_SEGMENT_SIZE - SMM_ENTRY_OFFSET - stub_size) / needed_ss_size;
+
+ if (cpus_per_segment == 0) {
+ printk(BIOS_ERR, "%s: CPUs won't fit in segment. Broken stub or save state size\n",
+ __func__);
return 0;
}
- if (ARRAY_SIZE(cpus) < num_cpus) {
- printk(BIOS_ERR,
- "%s: increase MAX_CPUS in Kconfig\n", __func__);
- return 0;
- }
-
- for (i = 0; i < num_cpus; i++) {
+ for (unsigned int i = 0; i < num_cpus; i++) {
+ if (i % cpus_per_segment == 0)
+ printk(BIOS_DEBUG, "-------------NEW CODE SEGMENT --------------\n");
printk(BIOS_DEBUG, "CPU 0x%x\n", i);
- cpus[i].smbase = base;
- cpus[i].entry = base + smm_entry_offset;
- printk(BIOS_DEBUG, " smbase %lx entry %lx\n", cpus[i].smbase,
- cpus[i].entry);
- cpus[i].ss_start = cpus[i].entry + (smm_entry_offset - ss_size);
+ /* We copy the same stub for each CPU so they all need the same 'smbase'. */
+ const size_t segment_number = i / cpus_per_segment;
+ cpus[i].smbase = smbase - SMM_CODE_SEGMENT_SIZE * segment_number
+ - needed_ss_size * (i % cpus_per_segment);
+ cpus[i].entry = cpus[i].smbase + SMM_ENTRY_OFFSET;
+ cpus[i].ss_start = cpus[i].smbase + SMM_CODE_SEGMENT_SIZE - needed_ss_size;
cpus[i].code_start = cpus[i].entry;
cpus[i].code_end = cpus[i].entry + stub_size;
- printk(BIOS_DEBUG, " ss_start %lx code_end %lx\n", cpus[i].ss_start,
+ printk(BIOS_DEBUG, " Stub [0x%lx-0x%lx[\n", cpus[i].code_start,
cpus[i].code_end);
+ printk(BIOS_DEBUG, " Save state [0x%lx-0x%lx[\n",
+ cpus[i].ss_start + needed_ss_size - params->real_cpu_save_state_size,
+ cpus[i].ss_start + needed_ss_size);
cpus[i].active = 1;
- base -= ss_size;
- seg_count++;
- if (seg_count >= cpus_in_segment) {
- base -= smm_entry_offset;
- seg_count = 0;
- printk(BIOS_DEBUG, "-------------NEW CODE SEGMENT --------------\n");
- }
}
return 1;