Probe HPET existence
QEMU does not provide a HPET block if it was configured with -no-hpet,
other machines SeaBIOS runs on may lack a HPET as well. Perform basic
checks the ID register for a reasonable vendor ID and a clock period
within the valid range, do not build the HPET table if that fails.
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
diff --git a/src/acpi.c b/src/acpi.c
index ea7b171..29160f4 100644
--- a/src/acpi.c
+++ b/src/acpi.c
@@ -158,6 +158,9 @@
} PACKED;
#define ACPI_HPET_ADDRESS 0xFED00000UL
+#define HPET_ID 0x000
+#define HPET_PERIOD 0x004
+
/*
* SRAT (NUMA topology description) table
*/
@@ -464,7 +467,16 @@
static void*
build_hpet(void)
{
- struct acpi_20_hpet *hpet = malloc_high(sizeof(*hpet));
+ struct acpi_20_hpet *hpet;
+ const void *hpet_base = (void *)ACPI_HPET_ADDRESS;
+ u32 hpet_vendor = readl(hpet_base + HPET_ID) >> 16;
+ u32 hpet_period = readl(hpet_base + HPET_PERIOD);
+
+ if (hpet_vendor == 0 || hpet_vendor == 0xffff ||
+ hpet_period == 0 || hpet_period > 0x05F5E100)
+ return NULL;
+
+ hpet = malloc_high(sizeof(*hpet));
if (!hpet) {
warn_noalloc();
return NULL;