[PATCH 6.6 118/142] x86/microcode: Clarify the late load logic

6.6-stable review patch. If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner tglx@linutronix.de

commit 6f059e634dcd0d725854514c94c114bbdd83950d upstream

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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/cpu/microcode/core.c | 41 ++++++++++++++++------------------- 1 file changed, 19 insertions(+), 22 deletions(-)

--- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -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);