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SubjectRe: [PATCH 1/4] x86: Do microcode updates at CPU_STARTING, not CPU_ONLINE
On Wed, Jun 13, 2012 at 01:20:39PM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
>
> Do microcode updates of resuming or newling plugged CPUs earlier
> in CPU_STARTING instead of later when ONLINE. This prevents races
> with parallel users who may need a microcode update to avoid some
> problem.
>
> Since we cannot request the microcode from udev at this stage,
> try to grab the microcode from another CPU. This is also more efficient
> because it avoids redundant loads. In addition to that
> it avoids the need for separate paths for resume and CPU bootup.
>
> This requires invalidating the microcodes on other CPUs on free.
> Each CPU does this in parallel, so it's not a big problem.
>
> When there is no good microcode available the update is delayed
> until the update can be requested. In the normal cases it should
> be available.
>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
> ---
> arch/x86/kernel/microcode_core.c | 65 +++++++++++++++++++++++++------------
> arch/x86/kernel/microcode_intel.c | 13 +++++++-
> 2 files changed, 56 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/kernel/microcode_core.c b/arch/x86/kernel/microcode_core.c
> index fbdfc69..f947ef7 100644
> --- a/arch/x86/kernel/microcode_core.c
> +++ b/arch/x86/kernel/microcode_core.c
> @@ -358,20 +358,7 @@ static void microcode_fini_cpu(int cpu)
> uci->valid = 0;
> }
>
> -static enum ucode_state microcode_resume_cpu(int cpu)
> -{
> - struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
> -
> - if (!uci->mc)
> - return UCODE_NFOUND;
> -
> - pr_debug("CPU%d updated upon resume\n", cpu);
> - apply_microcode_on_target(cpu);
> -
> - return UCODE_OK;
> -}
> -
> -static enum ucode_state microcode_init_cpu(int cpu)
> +static enum ucode_state microcode_init_cpu_late(int cpu)
> {
> enum ucode_state ustate;
>
> @@ -392,15 +379,44 @@ static enum ucode_state microcode_init_cpu(int cpu)
> return ustate;
> }
>
> -static enum ucode_state microcode_update_cpu(int cpu)
> +/* Grab ucode from another CPU */
> +static void clone_ucode_data(void)
> +{
> + int cpu = smp_processor_id();
> + int i;
> +
> + for_each_online_cpu (i) {
> + if (ucode_cpu_info[i].mc &&
> + ucode_cpu_info[i].valid &&
> + cpu_data(i).x86 == cpu_data(cpu).x86 &&
> + cpu_data(i).x86_model == cpu_data(cpu).x86_model) {
> + ucode_cpu_info[cpu].mc = ucode_cpu_info[i].mc;
> + break;
> + }
> + }
> +}
> +
> +static enum ucode_state microcode_init_cpu_early(int cpu)
> +{
> + clone_ucode_data();
> + /* We can request later when the CPU is online */
> + if (ucode_cpu_info[cpu].mc == NULL)
> + return UCODE_ERROR;
> + if (microcode_ops->collect_cpu_info(cpu, &ucode_cpu_info[cpu].cpu_sig))
> + return UCODE_ERROR;
> + if (microcode_ops->apply_microcode(smp_processor_id()))
> + pr_warn("CPU%d microcode update failed\n", cpu);
> + return UCODE_OK;
> +}

This is run only from the notifier and nothing is looking at its return
values. It should be returning void in such cases.

> +
> +static enum ucode_state microcode_update_cpu_late(int cpu)
> {
> struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
> enum ucode_state ustate;
>
> - if (uci->valid)
> - ustate = microcode_resume_cpu(cpu);
> - else
> - ustate = microcode_init_cpu(cpu);
> + /* Resume already done early */
> + if (!uci->valid)
> + ustate = microcode_init_cpu_late(cpu);
>
> return ustate;
> }
> @@ -418,7 +434,7 @@ static int mc_device_add(struct device *dev, struct subsys_interface *sif)
> if (err)
> return err;
>
> - if (microcode_init_cpu(cpu) == UCODE_ERROR)
> + if (microcode_init_cpu_late(cpu) == UCODE_ERROR)
> return -EINVAL;
>
> return err;
> @@ -468,9 +484,16 @@ mc_cpu_callback(struct notifier_block *nb, unsigned long action, void *hcpu)
>
> dev = get_cpu_device(cpu);
> switch (action) {
> + case CPU_STARTING:
> + case CPU_STARTING_FROZEN:
> + microcode_init_cpu_early(cpu);
> + break;
> +
> case CPU_ONLINE:
> case CPU_ONLINE_FROZEN:
> - microcode_update_cpu(cpu);
> + /* Retry again in case we couldn't request early */
> + if (cpu_data(cpu).microcode < ucode_cpu_info[cpu].cpu_sig.rev)
> + microcode_update_cpu_late(cpu);

This implies newer ucode versions are numerically higher than
what's currently present. And it is probably correct in the 99% of
the cases but it would be more correct IMHO to have "!=" there.
microcode_update_cpu_late takes care of checking the correct ucode
version anyway down the path.

--
Regards/Gruss,
Boris.


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