kernel.git/arch/x86/kernel/cpu/microcode, branch linux-4.16.y

x86/microcode: Do not exit early from __reload_late()

2018-05-01T19:47:30Z

commit 09e182d17e8891dd73baba961a0f5a82e9274c97 upstream. Vitezslav reported a case where the "Timeout during microcode update!" panic would hit. After a deeper look, it turned out that his .config had CONFIG_HOTPLUG_CPU disabled which practically made save_mc_for_early() a no-op. When that happened, the discovered microcode patch wasn't saved into the cache and the late loading path wouldn't find any. This, then, lead to early exit from __reload_late() and thus CPUs waiting until the timeout is reached, leading to the panic. In hindsight, that function should have been written so it does not return before the post-synchronization. Oh well, I know better now... Fixes: bb8c13d61a62 ("x86/microcode: Fix CPU synchronization routine") Reported-by: Vitezslav Samel Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Tested-by: Vitezslav Samel Tested-by: Ashok Raj Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20180418081140.GA2439@pc11.op.pod.cz Link: https://lkml.kernel.org/r/20180421081930.15741-2-bp@alien8.de Signed-off-by: Greg Kroah-Hartman

x86/microcode/intel: Save microcode patch unconditionally

2018-05-01T19:47:30Z

commit 84749d83758af6576552046b215b9b7f37f9556b upstream. save_mc_for_early() was a no-op on !CONFIG_HOTPLUG_CPU but the generic_load_microcode() path saves the microcode patches it has found into the cache of patches which is used for late loading too. Regardless of whether CPU hotplug is used or not. Make the saving unconditional so that late loading can find the proper patch. Reported-by: Vitezslav Samel Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Tested-by: Vitezslav Samel Tested-by: Ashok Raj Cc: stable@vger.kernel.org Link: http://lkml.kernel.org/r/20180418081140.GA2439@pc11.op.pod.cz Link: https://lkml.kernel.org/r/20180421081930.15741-1-bp@alien8.de Signed-off-by: Greg Kroah-Hartman

x86/microcode: Fix CPU synchronization routine

2018-03-16T19:55:51Z

Emanuel reported an issue with a hang during microcode update because my dumb idea to use one atomic synchronization variable for both rendezvous - before and after update - was simply bollocks: microcode: microcode_reload_late: late_cpus: 4 microcode: __reload_late: cpu 2 entered microcode: __reload_late: cpu 1 entered microcode: __reload_late: cpu 3 entered microcode: __reload_late: cpu 0 entered microcode: __reload_late: cpu 1 left microcode: Timeout while waiting for CPUs rendezvous, remaining: 1 CPU1 above would finish, leave and the others will still spin waiting for it to join. So do two synchronization atomics instead, which makes the code a lot more straightforward. Also, since the update is serialized and it also takes quite some time per microcode engine, increase the exit timeout by the number of CPUs on the system. That's ok because the moment all CPUs are done, that timeout will be cut short. Furthermore, panic when some of the CPUs timeout when returning from a microcode update: we can't allow a system with not all cores updated. Also, as an optimization, do not do the exit sync if microcode wasn't updated. Reported-by: Emanuel Czirai Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Tested-by: Emanuel Czirai Tested-by: Ashok Raj Tested-by: Tom Lendacky Link: https://lkml.kernel.org/r/20180314183615.17629-2-bp@alien8.de

x86/microcode: Attempt late loading only when new microcode is present

2018-03-16T19:55:51Z

Return UCODE_NEW from the scanning functions to denote that new microcode was found and only then attempt the expensive synchronization dance. Reported-by: Emanuel Czirai Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Tested-by: Emanuel Czirai Tested-by: Ashok Raj Tested-by: Tom Lendacky Link: https://lkml.kernel.org/r/20180314183615.17629-1-bp@alien8.de

x86/microcode: Synchronize late microcode loading

2018-03-08T09:19:26Z

Original idea by Ashok, completely rewritten by Borislav. Before you read any further: the early loading method is still the preferred one and you should always do that. The following patch is improving the late loading mechanism for long running jobs and cloud use cases. Gather all cores and serialize the microcode update on them by doing it one-by-one to make the late update process as reliable as possible and avoid potential issues caused by the microcode update. [ Borislav: Rewrite completely. ] Co-developed-by: Borislav Petkov Signed-off-by: Ashok Raj Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Tested-by: Tom Lendacky Tested-by: Ashok Raj Reviewed-by: Tom Lendacky Cc: Arjan Van De Ven Link: https://lkml.kernel.org/r/20180228102846.13447-8-bp@alien8.de

x86/microcode: Request microcode on the BSP

2018-03-08T09:19:26Z

... so that any newer version can land in the cache and can later be fished out by the application functions. Do that before grabbing the hotplug lock. Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Tested-by: Tom Lendacky Tested-by: Ashok Raj Reviewed-by: Tom Lendacky Cc: Arjan Van De Ven Link: https://lkml.kernel.org/r/20180228102846.13447-7-bp@alien8.de

x86/microcode/intel: Look into the patch cache first

2018-03-08T09:19:26Z

The cache might contain a newer patch - look in there first. A follow-on change will make sure newest patches are loaded into the cache of microcode patches. Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Tested-by: Tom Lendacky Tested-by: Ashok Raj Cc: Arjan Van De Ven Link: https://lkml.kernel.org/r/20180228102846.13447-6-bp@alien8.de

x86/microcode: Do not upload microcode if CPUs are offline

2018-03-08T09:19:26Z

Avoid loading microcode if any of the CPUs are offline, and issue a warning. Having different microcode revisions on the system at any time is outright dangerous. [ Borislav: Massage changelog. ] Signed-off-by: Ashok Raj Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Tested-by: Tom Lendacky Tested-by: Ashok Raj Reviewed-by: Tom Lendacky Cc: Arjan Van De Ven Link: http://lkml.kernel.org/r/1519352533-15992-4-git-send-email-ashok.raj@intel.com Link: https://lkml.kernel.org/r/20180228102846.13447-5-bp@alien8.de

x86/microcode/intel: Writeback and invalidate caches before updating microcode

2018-03-08T09:19:25Z

Updating microcode is less error prone when caches have been flushed and depending on what exactly the microcode is updating. For example, some of the issues around certain Broadwell parts can be addressed by doing a full cache flush. [ Borislav: Massage it and use native_wbinvd() in both cases. ] Signed-off-by: Ashok Raj Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Tested-by: Tom Lendacky Tested-by: Ashok Raj Cc: Arjan Van De Ven Link: http://lkml.kernel.org/r/1519352533-15992-3-git-send-email-ashok.raj@intel.com Link: https://lkml.kernel.org/r/20180228102846.13447-4-bp@alien8.de

x86/microcode/intel: Check microcode revision before updating sibling threads

2018-03-08T09:19:25Z

After updating microcode on one of the threads of a core, the other thread sibling automatically gets the update since the microcode resources on a hyperthreaded core are shared between the two threads. Check the microcode revision on the CPU before performing a microcode update and thus save us the WRMSR 0x79 because it is a particularly expensive operation. [ Borislav: Massage changelog and coding style. ] Signed-off-by: Ashok Raj Signed-off-by: Borislav Petkov Signed-off-by: Thomas Gleixner Tested-by: Tom Lendacky Tested-by: Ashok Raj Cc: Arjan Van De Ven Link: http://lkml.kernel.org/r/1519352533-15992-2-git-send-email-ashok.raj@intel.com Link: https://lkml.kernel.org/r/20180228102846.13447-3-bp@alien8.de