[S] Change in coreboot[main]: arch/x86/acpi_bert: Add spinlock

[Patrick Rudolph (Code Review)]

Patrick Rudolph has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/86539?usp=email )

Change subject: arch/x86/acpi_bert: Add spinlock
......................................................................

arch/x86/acpi_bert: Add spinlock

The code may be called in parallel from MPinit.
Add a spinlock to protect critical functions allocating and checking if
enough space is available.

Prevents using the same region for multiple entries and prevents
overallocation and possibly corrupting CBMEM.

TEST: Booted on amd/birman+ generating ACPI BERT tables.

Change-Id: Iab484149ef00797e1846441fb93407fe05ac8abb
Signed-off-by: Patrick Rudolph 
---
M src/arch/x86/acpi_bert_storage.c
1 file changed, 23 insertions(+), 4 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/39/86539/1

diff --git a/src/arch/x86/acpi_bert_storage.c b/src/arch/x86/acpi_bert_storage.c
index 62c0441..ce45984 100644
--- a/src/arch/x86/acpi_bert_storage.c
+++ b/src/arch/x86/acpi_bert_storage.c
@@ -9,6 +9,7 @@
 #include <acpi/acpi.h>
 #include <arch/bert_storage.h>
 #include <string.h>
+#include <smp/spinlock.h>
 #include <types.h>

/* BERT region management:  Allow the chipset to determine the specific
@@ -26,12 +27,20 @@
 static size_t bert_region_size;
 static size_t bert_region_used;

+DECLARE_SPIN_LOCK(acpi_bert_lock)
+
 /* Calculate the remaining space in the BERT region.  This knowledge may help
  * the caller prioritize the information to store.
  */
 size_t bert_storage_remaining(void)
 {
-	return bert_region_broken ? 0 : bert_region_size - bert_region_used;
+	size_t ret;
+
+	spin_lock(&acpi_bert_lock);
+	ret = bert_region_broken ? 0 : bert_region_size - bert_region_used;
+	spin_unlock(&acpi_bert_lock);
+
+	return ret;
 }

bool bert_errors_present(void)
@@ -48,23 +57,33 @@
    }

/* No metadata, etc. with our region, so this is easy */
+	spin_lock(&acpi_bert_lock);
    *start = bert_region_base;
    *size = bert_region_used;
+	spin_unlock(&acpi_bert_lock);
 }

static void *bert_allocate_storage(size_t size)
 {
    size_t alloc;
+	void *ret = NULL;
+
+	spin_lock(&acpi_bert_lock);

if (bert_region_broken)
-		return NULL;
+		goto out;
    if (bert_region_used + size > bert_region_size)
-		return NULL;
+		goto out;

alloc = bert_region_used;
    bert_region_used += size;

-	return (void *)((u8 *)bert_region_base + alloc);
+	ret = (void *)((u8 *)bert_region_base + alloc);
+
+out:
+	spin_unlock(&acpi_bert_lock);
+
+	return ret;
 }

/* Generic Error Status:  Each Status represents a unique error event within