Commit 6f059e63 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Borislav Petkov (AMD)
Browse files

x86/microcode: Clarify the late load logic 



reload_store() is way too complicated. Split the inner workings out and
make the following enhancements:

 - Taint the kernel only when the microcode was actually updated. If. e.g.
   the rendezvous fails, then nothing happened and there is no reason for
   tainting.

 - Return useful error codes

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: default avatarNikolay Borisov <nik.borisov@suse.com>
Link: https://lore.kernel.org/r/20231002115903.145048840@linutronix.de
parent 634ac23a

arch/x86/kernel/cpu/microcode/core.c

+19 −22
Original line number Diff line number Diff line
@@ -362,11 +362,11 @@ static int microcode_reload_late(void) 
		pr_info("Reload succeeded, microcode revision: 0x%x -> 0x%x\n",

			old, boot_cpu_data.microcode);

		microcode_check(&prev_info);

		add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);

	} else {

		pr_info("Reload failed, current microcode revision: 0x%x\n",

			boot_cpu_data.microcode);

	}



	return ret;

}
@@ -399,40 +399,37 @@ static bool ensure_cpus_are_online(void) 
	return true;

}



static int ucode_load_late_locked(void)

{

	if (!ensure_cpus_are_online())

		return -EBUSY;



	switch (microcode_ops->request_microcode_fw(0, &microcode_pdev->dev)) {

	case UCODE_NEW:

		return microcode_reload_late();

	case UCODE_NFOUND:

		return -ENOENT;

	default:

		return -EBADFD;

	}

}



static ssize_t reload_store(struct device *dev,

			    struct device_attribute *attr,

			    const char *buf, size_t size)

{

	enum ucode_state tmp_ret = UCODE_OK;

	int bsp = boot_cpu_data.cpu_index;

	unsigned long val;

	ssize_t ret = 0;

	ssize_t ret;



	ret = kstrtoul(buf, 0, &val);

	if (ret || val != 1)

		return -EINVAL;



	cpus_read_lock();



	if (!ensure_cpus_are_online()) {

		ret = -EBUSY;

		goto put;

	}



	tmp_ret = microcode_ops->request_microcode_fw(bsp, &microcode_pdev->dev);

	if (tmp_ret != UCODE_NEW)

		goto put;



	ret = microcode_reload_late();

put:

	ret = ucode_load_late_locked();

	cpus_read_unlock();



	if (ret == 0)

		ret = size;



	add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);



	return ret;

	return ret ? : size;

}



static DEVICE_ATTR_WO(reload);