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SubjectRe: [PATCH 12/30] x86, kaiser: map GDT into user page tables
On Mon, 20 Nov 2017, Andy Lutomirski wrote:
> On Mon, Nov 20, 2017 at 12:22 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
> > On Fri, 10 Nov 2017, Dave Hansen wrote:
> >> __set_fixmap(get_cpu_gdt_ro_index(cpu), get_cpu_gdt_paddr(cpu), prot);
> >> +
> >> + /* CPU 0's mapping is done in kaiser_init() */
> >> + if (cpu) {
> >> + int ret;
> >> +
> >> + ret = kaiser_add_mapping((unsigned long) get_cpu_gdt_ro(cpu),
> >> + PAGE_SIZE, __PAGE_KERNEL_RO);
> >> + /*
> >> + * We do not have a good way to fail CPU bringup.
> >> + * Just WARN about it and hope we boot far enough
> >> + * to get a good log out.
> >> + */
> >
> > The GDT fixmap can be set up before the CPU is started. There is no reason
> > to do that in cpu_init().
> >
> >> +
> >> + /*
> >> + * We could theoretically do this in setup_fixmap_gdt().
> >> + * But, we would need to rewrite the above page table
> >> + * allocation code to use the bootmem allocator. The
> >> + * buddy allocator is not available at the time that we
> >> + * call setup_fixmap_gdt() for CPU 0.
> >> + */
> >> + kaiser_add_user_map_early(get_cpu_gdt_ro(0), PAGE_SIZE,
> >> + __PAGE_KERNEL_RO | _PAGE_GLOBAL);
> >
> > This one is needs to stay.
>
> When you rebase on to my latest version, this should change to mapping
> the entire cpu_entry_area.

Too much flux left and right :)

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