Messages in this thread Patch in this message | | | Date | Thu, 29 Jan 2015 22:56:38 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 0/3]: x86, fpu: unlazy_fpu fixes/cleanups |
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On 01/29, Dave Hansen wrote: > > On 01/29/2015 01:33 PM, Oleg Nesterov wrote: > > On 01/29, Dave Hansen wrote: > >> > >> On 01/29/2015 01:07 PM, Oleg Nesterov wrote: > >>> On 01/23, Rik van Riel wrote: > >>>>> Not only is this broken with my new code, but it looks like it may > >>>>> be broken with the current code, too... > >>> Lets (try to) fix unlazy_fpu/save_init_fpu at least. > >>> > >>> Dave, fpu_save_init() in do_bounds() and task_get_bounds_dir() looks > >>> wrong too, shouldn't it use unlazy_fpu() ? See the changelog in 3/3. > >> > >> IIRC, the 'cpu_has_xsaveopt' on the CPUs that support will MPX will > >> enable eagerfpu. > > > > unless eagerfpu=off? but this doesn't matter. > > Yeah, that's true. That would also explain why I haven't run in to this > at all in testing. > > Ugh, fpu_save_init() says it isn't preempt safe anyway, so we shouldn't > be using it.
Yes, plus (I _think_) _init can add more problems.
> I'll send a fix.
How about the trivial patch below (on top of this series) ?
Oleg.
--- x/arch/x86/kernel/traps.c +++ x/arch/x86/kernel/traps.c @@ -313,7 +313,7 @@ dotraplinkage void do_bounds(struct pt_r * It is not directly accessible, though, so we need to * do an xsave and then pull it out of the xsave buffer. */ - fpu_save_init(&tsk->thread.fpu); + unlazy_fpu(tsk); xsave_buf = &(tsk->thread.fpu.state->xsave); bndcsr = get_xsave_addr(xsave_buf, XSTATE_BNDCSR); if (!bndcsr) --- x/arch/x86/mm/mpx.c +++ x/arch/x86/mm/mpx.c @@ -352,7 +352,7 @@ static __user void *task_get_bounds_dir( * The bounds directory pointer is stored in a register * only accessible if we first do an xsave. */ - fpu_save_init(&tsk->thread.fpu); + unlazy_fpu(tsk); bndcsr = get_xsave_addr(&tsk->thread.fpu.state->xsave, XSTATE_BNDCSR); if (!bndcsr) return MPX_INVALID_BOUNDS_DIR;
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