Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 1 Sep 2022 04:53:04 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH] x86/microcode/intel: Allow late loading only if a min rev is specified |
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On Mon, Aug 29, 2022 at 10:41:56PM +0000, Ashok Raj wrote: > But I suppose, you mean what refresh_hw is supposed to mean from the > existing code?
I've been meaning this for a while now.
> refresh_hw seems to imply when to update the copy of the microcode from > the filesystem. Also seems to imply late loading.
After your patch:
$ git grep refresh_fw arch/x86/ arch/x86/kernel/cpu/microcode/core.c:601:static enum ucode_state microcode_init_cpu(int cpu, bool refresh_fw) arch/x86/kernel/cpu/microcode/core.c:616: ustate = microcode_ops->request_microcode_fw(cpu, µcode_pdev->dev, refresh_fw);
$ git grep late_loading arch/x86/include/asm/microcode.h:36: bool late_loading); arch/x86/kernel/cpu/microcode/amd.c:894: bool late_loading) arch/x86/kernel/cpu/microcode/amd.c:903: if (!late_loading || !bsp) arch/x86/kernel/cpu/microcode/intel.c:166:static int microcode_sanity_check(void *mc, int print_err, bool late_loading) ...
Now you have both. More mess.
> its used in the following places. > > 1. During reload_store() where this is exclicitly due to echo 1 > reload > > tmp_ret = microcode_ops->request_microcode_fw(bsp, µcode_pdev->dev, true); > > Here passing true makes sense since you are going to do a full > refresh on all CPUs via late loading.
Yes, and here it is perfectly clear that it is late loading.
> 2. microcode_update_cpu() -> microcode_init_cpu()->request_microcode_fw(false) > > Early loading from resume.
CPU hotplug rather.
> So we would use the microcode cache to load from.
So this happens when the CPU is coming online. I'm not sure why I set it to "false" back then - whether it is because there's no filesystem yet or there was another reason. I *think* this was some contrived used case again.
In any case, this'll need to be experimented with to figure out what happens when it is set to "true".
> 3. mc_device_add() -> microcode_init_cpu(true)->request_microcode_fw(true) > > This seems like normal CPU hot-add, I'm not sure if refresh_fw=true is > valid. A new CPU should also use from the cache, but not a full reload > from filesystem. This could end up with new cpu with an updated ucode > and older with something that was loaded earlier.
Just check when mc_device_add() is actually called and then try to figure out what that actually does instead of speculating.
> Sort of what was fixed in: > commit 7189b3c11903667808029ec9766a6e96de5012a5 (tag: x86_microcode_for_v5.13)
That's a tag - not a git commit.
I think you mean
7189b3c11903 ("x86/microcode: Check for offline CPUs before requesting new microcode")
> intel.c doesn't seem to use this parameter at all today. But judging from > > amd.c: request_microcode_amd() > > /* reload ucode container only on the boot cpu */ > if (!refresh_fw || !bsp) > return UCODE_OK; > > Seems like it does the right job, since you would refresh only if > refresh_fw=true and its the bsp. Hence it seems immute to the > mc_device_add() bug.
I don't see a bug there.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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