On 2012-07-31 06:43 +0200, Ben Hutchings wrote:
> 3.2-stable review patch. If anyone has any objections, please let me know.
Alas, this does not build if CONFIG_SMP is unset:
,----
| arch/x86/kernel/microcode_core.c: In function 'reload_store':
| arch/x86/kernel/microcode_core.c:304:19: error: 'struct cpuinfo_x86' has no
member named 'cpu_index'
`----
Cheers,
Sven
> From: Borislav Petkov <borislav.pet...@amd.com>
>
> commit c9fc3f778a6a215ace14ee556067c73982b6d40f upstream.
>
> Microcode reloading in a per-core manner is a very bad idea for both
> major x86 vendors. And the thing is, we have such interface with which
> we can end up with different microcode versions applied on different
> cores of an otherwise homogeneous wrt (family,model,stepping) system.
>
> So turn off the possibility of doing that per core and allow it only
> system-wide.
>
> This is a minimal fix which we'd like to see in stable too thus the
> more-or-less arbitrary decision to allow system-wide reloading only on
> the BSP:
>
> $ echo 1 > /sys/devices/system/cpu/cpu0/microcode/reload
> ...
>
> and disable the interface on the other cores:
>
> $ echo 1 > /sys/devices/system/cpu/cpu23/microcode/reload
> -bash: echo: write error: Invalid argument
>
> Also, allowing the reload only from one CPU (the BSP in
> that case) doesn't allow the reload procedure to degenerate
> into an O(n^2) deal when triggering reloads from all
> /sys/devices/system/cpu/cpuX/microcode/reload sysfs nodes
> simultaneously.
>
> A more generic fix will follow.
>
> Cc: Henrique de Moraes Holschuh <h...@hmh.eng.br>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Signed-off-by: Borislav Petkov <borislav.pet...@amd.com>
> Link: http://lkml.kernel.org/r/1340280437-7718-2-git-send-email...@amd64.org
> Signed-off-by: H. Peter Anvin <h...@zytor.com>
> Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
> ---
> arch/x86/kernel/microcode_core.c | 26 +++++++++++++++++++-------
> 1 file changed, 19 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kernel/microcode_core.c
> b/arch/x86/kernel/microcode_core.c
> index fbdfc69..24b852b 100644
> --- a/arch/x86/kernel/microcode_core.c
> +++ b/arch/x86/kernel/microcode_core.c
> @@ -298,19 +298,31 @@ static ssize_t reload_store(struct device *dev,
> const char *buf, size_t size)
> {
> unsigned long val;
> - int cpu = dev->id;
> - ssize_t ret = 0;
> + int cpu;
> + ssize_t ret = 0, tmp_ret;
> +
> + /* allow reload only from the BSP */
> + if (boot_cpu_data.cpu_index != dev->id)
> + return -EINVAL;
>
> ret = kstrtoul(buf, 0, &val);
> if (ret)
> return ret;
>
> - if (val == 1) {
> - get_online_cpus();
> - if (cpu_online(cpu))
> - ret = reload_for_cpu(cpu);
> - put_online_cpus();
> + if (val != 1)
> + return size;
> +
> + get_online_cpus();
> + for_each_online_cpu(cpu) {
> + tmp_ret = reload_for_cpu(cpu);
> + if (tmp_ret != 0)
> + pr_warn("Error reloading microcode on CPU %d\n", cpu);
> +
> + /* save retval of the first encountered reload error */
> + if (!ret)
> + ret = tmp_ret;
> }
> + put_online_cpus();
>
> if (!ret)
> ret = size;
--
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