Re: [PATCH V2 1/2] x86/efi: Unmap EFI boot services code/data regions from efi_pgd

Peter Zijlstra
2018-10-29T14:41:03Z

On Fri, Oct 26, 2018 at 02:38:44PM -0700, Sai Praneeth Prakhya wrote:
> +int kernel_unmap_pages_in_pgd(pgd_t *pgd, unsigned long address,
> + unsigned long numpages)
> +{
> + int retval;
> +
> + /*
> + * The typical sequence for unmapping is to find a pte through
> + * lookup_address_in_pgd() (ideally, it should never return NULL because
> + * the address is already mapped) and change it's protections.
> + * As pfn is the *target* of a mapping, it's not useful while unmapping.
> + */
> + struct cpa_data cpa = {
> + .vaddr = &address,
> + .pgd = pgd,
> + .numpages = numpages,
> + .mask_set = __pgprot(0),
> + .mask_clr = __pgprot(_PAGE_PRESENT | _PAGE_RW),
> + .flags = 0,
> + };
> +
> + retval = __change_page_attr_set_clr(&cpa, 0);
> + __flush_tlb_all();

How is that not a TLB invalidation bug ?

> +
> + return retval;
> +}