On 05/08/2017 at 02:29 PM, Ingo Molnar wrote: > * Xunlei Pang <[email protected]> wrote: > >> On 05/05/2017 at 05:20 PM, Ingo Molnar wrote: >>> * Xunlei Pang <[email protected]> wrote: >>> >>>> On 05/05/2017 at 02:52 PM, Ingo Molnar wrote: >>>>> * Xunlei Pang <[email protected]> wrote: >>>>> >>>>>> @@ -122,6 +122,10 @@ static int init_pgtable(struct kimage *image, >>>>>> unsigned long start_pgtable) >>>>>> >>>>>> level4p = (pgd_t *)__va(start_pgtable); >>>>>> clear_page(level4p); >>>>>> + >>>>>> + if (direct_gbpages) >>>>>> + info.direct_gbpages = true; >>>>> No, this should be keyed off the CPU feature (X86_FEATURE_GBPAGES) >>>>> automatically, >>>>> not set blindly! AFAICS this patch will crash kexec on any CPU that does >>>>> not >>>>> support gbpages. >>>> It should be fine, probe_page_size_mask() already takes care of this: >>>> if (direct_gbpages && boot_cpu_has(X86_FEATURE_GBPAGES)) { >>>> printk(KERN_INFO "Using GB pages for direct mapping\n"); >>>> page_size_mask |= 1 << PG_LEVEL_1G; >>>> } else { >>>> direct_gbpages = 0; >>>> } >>>> >>>> So if X86_FEATURE_GBPAGES is not supported, direct_gbpages will be set to >>>> 0. >>> So why is the introduction of the info.direct_gbpages flag necessary? >>> AFAICS it >>> just duplicates the kernel's direct_gbpages flag. One outcome is that >>> hibernation >>> won't use gbpages, which is silly. >> boot/compressed/pagetable.c also uses kernel_ident_mapping_init() for kaslr, >> at >> the moment we don't have "direct_gbpages" definition or X86_FEATURE_GBPAGES >> feature detection. >> >> I thought that we can change the other call sites when found really needed. > Ok, you are right - I'll use the original patches as submitted, with the > updated > changelogs.
Thanks! Regards, Xunlei
