[v2 03/13] x86/microcode/intel: Fix a hang if early loading microcode fails
From: Ashok Raj
Date: Thu Nov 03 2022 - 14:00:18 EST
When early loading of microcode fails for any reason other than the wrong
family-model-stepping, Linux can get into an infinite loop retrying the
same failed load.
A single retry is needed to handle any mixed stepping case.
Assume we have a microcode that fails to load for some reason.
load_ucode_ap() seems to retry if the loading fails. But it searches for
a new rev, but ends up finding the same copy. Hence it appears to repeat
the same load, retry loop for ever.
load_ucode_intel_ap()
{
..
reget:
if (!*iup) {
patch = __load_ucode_intel(&uci);
^^^^^ Finds the same patch every time.
if (!patch)
return;
*iup = patch;
}
uci.mc = *iup;
if (apply_microcode_early(&uci, true)) {
^^^^^^^^^^^^ apply fails
/* Mixed-silicon system? Try to refetch the proper patch: */
*iup = NULL;
goto reget;
^^^^^ Rince repeat.
}
}
Fixes: 06b8534cb728 ("x86/microcode: Rework microcode loading")
Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx>
---
arch/x86/kernel/cpu/microcode/intel.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c
index 733b5eac0444..8ef04447fcf0 100644
--- a/arch/x86/kernel/cpu/microcode/intel.c
+++ b/arch/x86/kernel/cpu/microcode/intel.c
@@ -606,6 +606,7 @@ void __init load_ucode_intel_bsp(void)
{
struct microcode_intel *patch;
struct ucode_cpu_info uci;
+ int rev, ret;
patch = __load_ucode_intel(&uci);
if (!patch)
@@ -613,13 +614,18 @@ void __init load_ucode_intel_bsp(void)
uci.mc = patch;
- apply_microcode_early(&uci, true);
+ ret = apply_microcode_early(&uci, true);
+ if (ret) {
+ rev = patch->hdr.rev;
+ pr_err("Revision 0x%x failed during early loading\n", rev);
+ }
}
void load_ucode_intel_ap(void)
{
struct microcode_intel *patch, **iup;
struct ucode_cpu_info uci;
+ bool retried = false;
if (IS_ENABLED(CONFIG_X86_32))
iup = (struct microcode_intel **) __pa_nodebug(&intel_ucode_patch);
@@ -638,9 +644,13 @@ void load_ucode_intel_ap(void)
uci.mc = *iup;
if (apply_microcode_early(&uci, true)) {
+ if (retried)
+ return;
+
/* Mixed-silicon system? Try to refetch the proper patch: */
*iup = NULL;
+ retried = true;
goto reget;
}
}
--
2.34.1