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Wed, 10 Apr 2024 09:50:20 +0100 Date: Wed, 10 Apr 2024 09:50:20 +0100 Message-ID: <86v84psisz.wl-maz@kernel.org> From: Marc Zyngier To: Ryan Roberts Cc: Gavin Shan , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, oliver.upton@linux.dev, apopple@nvidia.com, rananta@google.com, mark.rutland@arm.com, v-songbaohua@oppo.com, yangyicong@hisilicon.com, shahuang@redhat.com, yihyu@redhat.com, shan.gavin@gmail.com Subject: Re: [PATCH v3 3/3] arm64: tlb: Allow range operation for MAX_TLBI_RANGE_PAGES In-Reply-To: <27718d41-32cb-4976-b50e-e9237da7aedf@arm.com> References: <20240405035852.1532010-1-gshan@redhat.com> <20240405035852.1532010-4-gshan@redhat.com> <27718d41-32cb-4976-b50e-e9237da7aedf@arm.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/29.2 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: ryan.roberts@arm.com, gshan@redhat.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will@kernel.org, akpm@linux-foundation.org, oliver.upton@linux.dev, apopple@nvidia.com, rananta@google.com, mark.rutland@arm.com, v-songbaohua@oppo.com, yangyicong@hisilicon.com, shahuang@redhat.com, yihyu@redhat.com, shan.gavin@gmail.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240410_015024_657775_3C4EC255 X-CRM114-Status: GOOD ( 24.64 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 08 Apr 2024 09:43:44 +0100, Ryan Roberts wrote: > > On 05/04/2024 04:58, Gavin Shan wrote: > > MAX_TLBI_RANGE_PAGES pages is covered by SCALE#3 and NUM#31 and it's > > supported now. Allow TLBI RANGE operation when the number of pages is > > equal to MAX_TLBI_RANGE_PAGES in __flush_tlb_range_nosync(). > > > > Suggested-by: Marc Zyngier > > Signed-off-by: Gavin Shan > > Reviewed-by: Ryan Roberts > > > --- > > arch/arm64/include/asm/tlbflush.h | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h > > index 243d71f7bc1f..95fbc8c05607 100644 > > --- a/arch/arm64/include/asm/tlbflush.h > > +++ b/arch/arm64/include/asm/tlbflush.h > > @@ -446,11 +446,11 @@ static inline void __flush_tlb_range_nosync(struct vm_area_struct *vma, > > * When not uses TLB range ops, we can handle up to > > * (MAX_DVM_OPS - 1) pages; > > * When uses TLB range ops, we can handle up to > > - * (MAX_TLBI_RANGE_PAGES - 1) pages. > > + * MAX_TLBI_RANGE_PAGES pages. > > */ > > if ((!system_supports_tlb_range() && > > (end - start) >= (MAX_DVM_OPS * stride)) || > > - pages >= MAX_TLBI_RANGE_PAGES) { > > + pages > MAX_TLBI_RANGE_PAGES) { > > As a further enhancement, I wonder if it might be better to test: > > pages * 4 / MAX_TLBI_RANGE_PAGES > MAX_DVM_OPS > > Then add an extra loop over __flush_tlb_range_op(), like KVM does. > > The math is trying to express that there are a maximum of 4 tlbi range > instructions for MAX_TLBI_RANGE_PAGES pages (1 per scale) and we only need to > fall back to flushing the whole mm if it could generate more than MAX_DVM_OPS ops. That'd be a good enhancement indeed, although I wonder if that occurs as often as we see it on the KVM side. But in any case, adding consistency amongst the users of __flush_tlb_range_op() can only be beneficial. Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel