| Message ID | 20190118164610.8123-2-julien.grall@arm.com (mailing list archive) |
|---|---|
| State | RFC |
| Headers | show |
| Series | arm64/sve: First steps towards optimizing syscalls | expand |
On Fri, Jan 18, 2019 at 04:46:03PM +0000, Julien Grall wrote: > TIF_SVE is cleared by fpsimd_restore_current_state() not > task_fpsimd_load(). Update the documentatio of do_sve_acc to reflect > this behavior. AFAICT (in v5.0-rc2), fpsimd_restore_current_state() clears TIF_FOREIGN_FPSTATE, not TIF_SVE. I think you mean that fpsimd_restore_current_state() enabled/disables the trap (via fpsimd_bind_task_to_cpu()), based on TIF_SVE. Is that right? Thanks, Mark. > > Signed-off-by: Julien Grall <julien.grall@arm.com> > --- > arch/arm64/kernel/fpsimd.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c > index 5ebe73b69961..b3870905a492 100644 > --- a/arch/arm64/kernel/fpsimd.c > +++ b/arch/arm64/kernel/fpsimd.c > @@ -799,7 +799,7 @@ void fpsimd_release_task(struct task_struct *dead_task) > * the SVE access trap will be disabled the next time this task > * reaches ret_to_user. > * > - * TIF_SVE should be clear on entry: otherwise, task_fpsimd_load() > + * TIF_SVE should be clear on entry: otherwise, fpsimd_restore_current_state() > * would have disabled the SVE access trap for userspace during > * ret_to_user, making an SVE access trap impossible in that case. > */ > -- > 2.11.0 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
Hi Mark, On 1/21/19 12:13 PM, Mark Rutland wrote: > On Fri, Jan 18, 2019 at 04:46:03PM +0000, Julien Grall wrote: >> TIF_SVE is cleared by fpsimd_restore_current_state() not >> task_fpsimd_load(). Update the documentatio of do_sve_acc to reflect >> this behavior. > > AFAICT (in v5.0-rc2), fpsimd_restore_current_state() clears > TIF_FOREIGN_FPSTATE, not TIF_SVE. > > I think you mean that fpsimd_restore_current_state() enabled/disables > the trap (via fpsimd_bind_task_to_cpu()), based on TIF_SVE. Is that > right? That's correct. I will reword the commit message and the documentation below. Cheers,
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index 5ebe73b69961..b3870905a492 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -799,7 +799,7 @@ void fpsimd_release_task(struct task_struct *dead_task) * the SVE access trap will be disabled the next time this task * reaches ret_to_user. * - * TIF_SVE should be clear on entry: otherwise, task_fpsimd_load() + * TIF_SVE should be clear on entry: otherwise, fpsimd_restore_current_state() * would have disabled the SVE access trap for userspace during * ret_to_user, making an SVE access trap impossible in that case. */
TIF_SVE is cleared by fpsimd_restore_current_state() not task_fpsimd_load(). Update the documentatio of do_sve_acc to reflect this behavior. Signed-off-by: Julien Grall <julien.grall@arm.com> --- arch/arm64/kernel/fpsimd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)