On Tue, Jul 21, 2015 at 7:01 PM, Brian Gerst <brgerst@gmail.com> wrote:
> On Tue, Jul 21, 2015 at 3:59 PM, Andy Lutomirski <luto@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.
> --
> Brian Gerst
--
Andy Lutomirski
AMA Capital Management, LLC
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> On Tue, Jul 21, 2015 at 3:59 PM, Andy Lutomirski <luto@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.
> --
> Brian Gerst
--
Andy Lutomirski
AMA Capital Management, LLC
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
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