4.15-stable review patch. If anyone has any objections, please let me know.
------------------ From: Ashok Raj <[email protected]> commit 30ec26da9967d0d785abc24073129a34c3211777 upstream. Avoid loading microcode if any of the CPUs are offline, and issue a warning. Having different microcode revisions on the system at any time is outright dangerous. [ Borislav: Massage changelog. ] Signed-off-by: Ashok Raj <[email protected]> Signed-off-by: Borislav Petkov <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Tested-by: Tom Lendacky <[email protected]> Tested-by: Ashok Raj <[email protected]> Reviewed-by: Tom Lendacky <[email protected]> Cc: Arjan Van De Ven <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Link: https://lkml.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/x86/kernel/cpu/microcode/core.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -486,6 +486,16 @@ static void __exit microcode_dev_exit(vo /* fake device for request_firmware */ static struct platform_device *microcode_pdev; +static int check_online_cpus(void) +{ + if (num_online_cpus() == num_present_cpus()) + return 0; + + pr_err("Not all CPUs online, aborting microcode update.\n"); + + return -EINVAL; +} + static enum ucode_state reload_for_cpu(int cpu) { struct ucode_cpu_info *uci = ucode_cpu_info + cpu; @@ -519,7 +529,13 @@ static ssize_t reload_store(struct devic return size; get_online_cpus(); + + ret = check_online_cpus(); + if (ret) + goto put; + mutex_lock(µcode_mutex); + for_each_online_cpu(cpu) { tmp_ret = reload_for_cpu(cpu); if (tmp_ret > UCODE_NFOUND) { @@ -538,6 +554,8 @@ static ssize_t reload_store(struct devic microcode_check(); mutex_unlock(µcode_mutex); + +put: put_online_cpus(); if (!ret)
