From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD480C10F13 for ; Tue, 16 Apr 2019 11:53:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 93B1820821 for ; Tue, 16 Apr 2019 11:53:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728725AbfDPLxL (ORCPT ); Tue, 16 Apr 2019 07:53:11 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:53478 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725787AbfDPLxL (ORCPT ); Tue, 16 Apr 2019 07:53:11 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5BF87EBD; Tue, 16 Apr 2019 04:53:10 -0700 (PDT) Received: from e103592.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6BF693F706; Tue, 16 Apr 2019 04:53:08 -0700 (PDT) Date: Tue, 16 Apr 2019 12:53:06 +0100 From: Dave Martin To: Julien Grall Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, ard.biesheuvel@linaro.org, julien.thierry@arm.com, marc.zyngier@arm.com, catalin.marinas@arm.com, suzuki.poulose@arm.com, will.deacon@arm.com, christoffer.dall@arm.com, james.morse@arm.com Subject: Re: [PATCH v2 2/3] arch/arm64: fpsimd: Introduce fpsimd_save_and_flush_cpu_state() and use it Message-ID: <20190416115305.GL3567@e103592.cambridge.arm.com> References: <20190412171420.29065-1-julien.grall@arm.com> <20190412171420.29065-3-julien.grall@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190412171420.29065-3-julien.grall@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 12, 2019 at 06:14:19PM +0100, Julien Grall wrote: > The only external user of fpsimd_save() and fpsimd_flush_cpu_state() is > the KVM FPSIMD code. > > A follow-up patch will mandate hold of the FPSIMD context while This is a bit hard to read without understanding the following patch. Maybe elaborate a bit with something like "The following patch will introduce a mechanism to acquire ownership of the FPSIMD/SVE context for performing context management operations. Rather than having to export this [...]" > modifying it. Rather than having to export the new helpers to get/put > the context, we can just introduce a new function to combine > fpsimd_save() and fpsimd_flush_cpu_state(). > > This has also the advantage to remove any external call of fpsimd_save() > and fpsimd_flush_cpu_state(), so they can be turned static. > > Lastly, the new function can also be used in the PM notifier. > > Signed-off-by: Julien Grall > > --- > Changes in v2: > - Patch added > --- > arch/arm64/include/asm/fpsimd.h | 5 ++--- > arch/arm64/kernel/fpsimd.c | 17 +++++++++++++---- > arch/arm64/kvm/fpsimd.c | 3 +-- > 3 files changed, 16 insertions(+), 9 deletions(-) > > diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h > index 32abbfd852e8..88c223f6ded6 100644 > --- a/arch/arm64/include/asm/fpsimd.h > +++ b/arch/arm64/include/asm/fpsimd.h > @@ -48,11 +48,11 @@ struct task_struct; > extern void fpsimd_save_state(struct user_fpsimd_state *state); > extern void fpsimd_load_state(struct user_fpsimd_state *state); > > -extern void fpsimd_save(void); > - > extern void fpsimd_thread_switch(struct task_struct *next); > extern void fpsimd_flush_thread(void); > > +extern void fpsimd_save_and_flush_cpu_state(void); > + Nit, bit I think this makes more sense alongside the other flush functions. Can you just drop this new declaration in place of the old declaration for sve_flush_cpu_state()? > extern void fpsimd_signal_preserve_current_state(void); > extern void fpsimd_preserve_current_state(void); > extern void fpsimd_restore_current_state(void); > @@ -63,7 +63,6 @@ extern void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *state, > void *sve_state, unsigned int sve_vl); > > extern void fpsimd_flush_task_state(struct task_struct *target); > -extern void fpsimd_flush_cpu_state(void); > > /* Maximum VL that SVE VL-agnostic software can transparently support */ > #define SVE_VL_ARCH_MAX 0x100 > diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c > index 577296bba730..9e4e4b6acd93 100644 > --- a/arch/arm64/kernel/fpsimd.c > +++ b/arch/arm64/kernel/fpsimd.c > @@ -241,7 +241,7 @@ static void task_fpsimd_load(void) > * > * Softirqs (and preemption) must be disabled. > */ > -void fpsimd_save(void) > +static void fpsimd_save(void) > { > struct fpsimd_last_state_struct const *last = > this_cpu_ptr(&fpsimd_last_state); > @@ -1117,12 +1117,22 @@ void fpsimd_flush_task_state(struct task_struct *t) > * Invalidate any task's FPSIMD state that is present on this cpu. > * This function must be called with softirqs disabled. > */ > -void fpsimd_flush_cpu_state(void) > +static void fpsimd_flush_cpu_state(void) > { > __this_cpu_write(fpsimd_last_state.st, NULL); > set_thread_flag(TIF_FOREIGN_FPSTATE); > } > > +/* > + * Save the FPSIMD state to memory and invalidate cpu view. > + * This function must be called with softirqs (and preemption) disabled. > + */ > +void fpsimd_save_and_flush_cpu_state(void) > +{ > + fpsimd_save(); > + fpsimd_flush_cpu_state(); > +} > + > #ifdef CONFIG_KERNEL_MODE_NEON > > DEFINE_PER_CPU(bool, kernel_neon_busy); > @@ -1279,8 +1289,7 @@ static int fpsimd_cpu_pm_notifier(struct notifier_block *self, > { > switch (cmd) { > case CPU_PM_ENTER: > - fpsimd_save(); > - fpsimd_flush_cpu_state(); > + fpsimd_save_and_flush_cpu_state(); Any reason not to do this in kernel_neon_begin() too? > break; > case CPU_PM_EXIT: > break; > diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c > index 6e3c9c8b2df9..01bd2e862506 100644 > --- a/arch/arm64/kvm/fpsimd.c > +++ b/arch/arm64/kvm/fpsimd.c > @@ -113,8 +113,7 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) > u64 *guest_zcr = &vcpu->arch.ctxt.sys_regs[ZCR_EL1]; > > /* Clean guest FP state to memory and invalidate cpu view */ You can lose the comment here, since the call is now self-explanatory. > - fpsimd_save(); > - fpsimd_flush_cpu_state(); > + fpsimd_save_and_flush_cpu_state(); [...] Otherwise, looks sensible. Cheers ---Dave