Hi Ard, On Mon, Dec 04, 2017 at 04:01:09PM +0000, Ard Biesheuvel wrote: > On 4 December 2017 at 14:13, Steve Capper <steve.capper@xxxxxxx> wrote: > > update_mapping_prot assumes that it will be used on the VA for the > > kernel .text section. (Via the check virt >= VMALLOC_START) > > > > Recent kdump patches employ this function to modify the protection of > > the direct linear mapping (which is strictly speaking outside of this > > area), via mark_linear_text_alias_ro(.). > > > > Isn't that a bug? Is it guaranteed that those protection attributes > can be modified without splitting live page tables, and the resulting > risk of TLB conflicts? IIUC there is a bug in my earlier patch to flip the kernel VA space round, it should allow addresses from the linear mapping to be processed by update_mapping_prot. I'll update the logic in VA flip patch, so this patch can be removed from the series. It is not apparent to me how mark_linear_text_alias_ro(.) guarantees that no page table entries for the linear map are split, though. Cheers, -- Steve _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
