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Re: [PATCH 12/27] arm64/sve: Support vector length resetting for new processes

• From: Dave Martin <Dave dot Martin at arm dot com>
• To: Alex Bennée <alex dot bennee at linaro dot org>
• Cc: linux-arch at vger dot kernel dot org, libc-alpha at sourceware dot org,Ard Biesheuvel <ard dot biesheuvel at linaro dot org>,Szabolcs Nagy <szabolcs dot nagy at arm dot com>,Catalin Marinas <catalin dot marinas at arm dot com>,Will Deacon <will dot deacon at arm dot com>,Richard Sandiford <richard dot sandiford at arm dot com>,kvmarm at lists dot cs dot columbia dot edu, linux-arm-kernel at lists dot infradead dot org
• Date: Tue, 22 Aug 2017 18:22:24 +0100
• Subject: Re: [PATCH 12/27] arm64/sve: Support vector length resetting for new processes
• Authentication-results: sourceware.org; auth=none
• References: <1502280338-23002-1-git-send-email-Dave.Martin@arm.com> <1502280338-23002-13-git-send-email-Dave.Martin@arm.com> <871so3bmj0.fsf@linaro.org>

On Tue, Aug 22, 2017 at 05:22:11PM +0100, Alex Bennée wrote:> > Dave Martin <Dave.Martin@arm.com> writes:> > > It's desirable to be able to reset the vector length to some sane> > default for new processes, since the new binary and its libraries> > processes may or may not be SVE-aware.> >> > This patch tracks the desired post-exec vector length (if any) in a> > new thread member sve_vl_onexec, and adds a new thread flag> > TIF_SVE_VL_INHERIT to control whether to inherit or reset the> > vector length.  Currently these are inactive.  Subsequent patches> > will provide the capability to configure them.> >> > Signed-off-by: Dave Martin <Dave.Martin@arm.com>> > ---> >  arch/arm64/include/asm/processor.h   |  1 +> >  arch/arm64/include/asm/thread_info.h |  1 +> >  arch/arm64/kernel/fpsimd.c           | 13 +++++++++++++> >  3 files changed, 15 insertions(+)> >> > diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h> > index 969feed..da8802a 100644> > --- a/arch/arm64/include/asm/processor.h> > +++ b/arch/arm64/include/asm/processor.h> > @@ -87,6 +87,7 @@ struct thread_struct {> >  struct fpsimd_statefpsimd_state;> >  void*sve_state;/* SVE registers, if any */> >  u16sve_vl;/* SVE vector length */> > +u16sve_vl_onexec;/* SVE vl after next> > exec */> > Inconsistent size usage here as well...Agreed, the same history applies as for sve_vl.  I'll replace this withan unsigned int.[...]Cheers---Dave

• References:
  • [PATCH 00/27] ARM Scalable Vector Extension (SVE)
    • From: Dave Martin
  • [PATCH 12/27] arm64/sve: Support vector length resetting for new processes
    • From: Dave Martin
  • Re: [PATCH 12/27] arm64/sve: Support vector length resetting for new processes
    • From: Alex Bennée