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x86/microcode: Clarify the late load logic

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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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Nikolay Borisov <nik.borisov@suse.com>
Link: https://lore.kernel.org/r/20231002115903.145048840@linutronix.de
This commit is contained in:
Thomas Gleixner 2023-10-02 13:59:57 +02:00 committed by Borislav Petkov (AMD)
parent 634ac23ad6
commit 6f059e634d
1 changed files with 19 additions and 22 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

41
arch/x86/kernel/cpu/microcode/core.c
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@ -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);