6.6-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Gleixner tglx@linutronix.de
commit ba3aeb97cb2c53025356f31c5a0a294385194115 upstream
Add a per CPU control field to ucode_ctrl and define constants for it which are going to be used to control the loading state machine.
In theory this could be a global control field, but a global control does not cover the following case:
15 primary CPUs load microcode successfully 1 primary CPU fails and returns with an error code
With global control the sibling of the failed CPU would either try again or the whole operation would be aborted with the consequence that the 15 siblings do not invoke the apply path and end up with inconsistent software state. The result in dmesg would be inconsistent too.
There are two additional fields added and initialized:
ctrl_cpu and secondaries. ctrl_cpu is the CPU number of the primary thread for now, but with the upcoming uniform loading at package or system scope this will be one CPU per package or just one CPU. Secondaries hands the control CPU a CPU mask which will be required to release the secondary CPUs out of the wait loop.
Preparatory change for implementing a properly split control flow for primary and secondary CPUs.
Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Link: https://lore.kernel.org/r/20231002115903.319959519@linutronix.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/cpu/microcode/core.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-)
--- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -252,8 +252,19 @@ static struct platform_device *microcode * requirement can be relaxed in the future. Right now, this is conservative * and good. */ +enum sibling_ctrl { + /* Spinwait with timeout */ + SCTRL_WAIT, + /* Invoke the microcode_apply() callback */ + SCTRL_APPLY, + /* Proceed without invoking the microcode_apply() callback */ + SCTRL_DONE, +}; + struct microcode_ctrl { + enum sibling_ctrl ctrl; enum ucode_state result; + unsigned int ctrl_cpu; };
static DEFINE_PER_CPU(struct microcode_ctrl, ucode_ctrl); @@ -398,7 +409,7 @@ static int load_late_stop_cpus(void) */ static bool setup_cpus(void) { - struct microcode_ctrl ctrl = { .result = -1, }; + struct microcode_ctrl ctrl = { .ctrl = SCTRL_WAIT, .result = -1, }; unsigned int cpu;
for_each_cpu_and(cpu, cpu_present_mask, &cpus_booted_once_mask) { @@ -408,7 +419,12 @@ static bool setup_cpus(void) return false; } } - /* Initialize the per CPU state */ + + /* + * Initialize the per CPU state. This is core scope for now, + * but prepared to take package or system scope into account. + */ + ctrl.ctrl_cpu = cpumask_first(topology_sibling_cpumask(cpu)); per_cpu(ucode_ctrl, cpu) = ctrl; } return true;