On Tue, Jul 21, 2015 at 10:12 PM, Andy Lutomirski <l...@amacapital.net> wrote: > On Tue, Jul 21, 2015 at 7:01 PM, Brian Gerst <brge...@gmail.com> wrote: >> On Tue, Jul 21, 2015 at 3:59 PM, Andy Lutomirski <l...@kernel.org> wrote: >>> modify_ldt has questionable locking and does not synchronize >>> threads. Improve it: redesign the locking and synchronize all >>> threads' LDTs using an IPI on all modifications. >> >> What does this fix? I can see sending an IPI if the LDT is >> reallocated, but on every update seems unnecessary. >> > > It prevents nastiness in which you're in user mode with an impossible > CS or SS, resulting in potentially interesting artifacts in > interrupts, NMIs, etc.
By impossible, do you mean a partially updated descriptor when the interrupt occurs? Would making sure that the descriptor is atomically updated (using set_64bit()) fix that? -- Brian Gerst -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
