Messages in this thread Patch in this message | | | From | Ashok Raj <> | Subject | [Patch V1 2/7] x86/microcode/intel: Remove retries on early microcode load | Date | Tue, 29 Nov 2022 13:08:27 -0800 |
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Microcode loading can fail. This happens today when handling mixed steppings. But it can also happen for other reasons such as corrupted image, Security Version Number (SVN) preventing anti-rollback, dependencies on BIOS loaded microcode image for some capabilities.
When the microcode loading fails, the kernel will quietly hang at boot. This has been observed by end users (Links below) who had to revert their microcode packages in order to boot again.
The hang is due to an infinite retry loop. The retries were in place to support systems with mixed steppings. Now that mixed steppings are no longer supported, there is only one microcode image at a time. Any retries will simply reattempt to apply the same image over and over without making progress.
Some possible past bugs that could be due to this bug are below.
There is no direct evidence that these end user issues were caused by this retry loop. However, the early boot hangs along with reverting the microcode update workaround provide strong circumstantial evidence to support the theory that they are linked.
Remove the retry loop and only attempt to apply microcode once.
Link: https://bugs.launchpad.net/ubuntu/+source/intel-microcode/+bug/1911959 Link: https://forums.linuxmint.com/viewtopic.php?p=1827032#1827032 Link: https://askubuntu.com/questions/1291486/boot-crash-after-latest-update-of-intel-microcode-nov-11-2020 Fixes: 06b8534cb728 ("x86/microcode: Rework microcode loading") Cc: stable@vger.kernel.org Signed-off-by: Ashok Raj <ashok.raj@intel.com> --- arch/x86/kernel/cpu/microcode/intel.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-)
diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c index 4f93875f57b4..d68b084a17e7 100644 --- a/arch/x86/kernel/cpu/microcode/intel.c +++ b/arch/x86/kernel/cpu/microcode/intel.c @@ -495,7 +495,6 @@ void load_ucode_intel_ap(void) else iup = &intel_ucode_patch; -reget: if (!*iup) { patch = __load_ucode_intel(&uci); if (!patch) @@ -505,13 +504,7 @@ void load_ucode_intel_ap(void) } uci.mc = *iup; - - if (apply_microcode_early(&uci, true)) { - /* Mixed-silicon system? Try to refetch the proper patch: */ - *iup = NULL; - - goto reget; - } + apply_microcode_early(&uci, true); } static struct microcode_intel *find_patch(struct ucode_cpu_info *uci) -- 2.34.1
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