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[88.208.79.100]) by smtp.gmail.com with ESMTPSA id d186sm10217607wmf.7.2019.11.28.00.48.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 28 Nov 2019 00:48:02 -0800 (PST) Sender: Michal Meloun Reply-To: meloun.michal@gmail.com Subject: Re: svn commit: r355145 - head/sys/arm64/arm64 To: Alan Cox , src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org References: <201911272033.xARKXowX014908@repo.freebsd.org> From: Michal Meloun Message-ID: Date: Thu, 28 Nov 2019 09:48:04 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <201911272033.xARKXowX014908@repo.freebsd.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 47NrrP3y01z4GfX X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org; dkim=pass header.d=gmail.com header.s=20161025 header.b=k7TKmYOS; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (mx1.freebsd.org: domain of melounmichal@gmail.com designates 2a00:1450:4864:20::42e as permitted sender) smtp.mailfrom=melounmichal@gmail.com X-Spamd-Result: default: False [-3.00 / 15.00]; RCVD_VIA_SMTP_AUTH(0.00)[]; HAS_REPLYTO(0.00)[meloun.michal@gmail.com]; TO_DN_SOME(0.00)[]; R_SPF_ALLOW(-0.20)[+ip6:2a00:1450:4000::/36]; FREEMAIL_FROM(0.00)[gmail.com]; RCVD_COUNT_THREE(0.00)[3]; DKIM_TRACE(0.00)[gmail.com:+]; DMARC_POLICY_ALLOW(-0.50)[gmail.com,none]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; FREEMAIL_ENVFROM(0.00)[gmail.com]; ASN(0.00)[asn:15169, ipnet:2a00:1450::/32, country:US]; TAGGED_FROM(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; DWL_DNSWL_NONE(0.00)[gmail.com.dwl.dnswl.org : 127.0.5.0]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; R_DKIM_ALLOW(-0.20)[gmail.com:s=20161025]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; TO_MATCH_ENVRCPT_ALL(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; MIME_GOOD(-0.10)[text/plain]; FREEMAIL_REPLYTO(0.00)[gmail.com]; REPLYTO_DOM_EQ_FROM_DOM(0.00)[]; IP_SCORE_FREEMAIL(0.00)[]; IP_SCORE(0.00)[ip: (-9.04), ipnet: 2a00:1450::/32(-2.69), asn: 15169(-1.95), country: US(-0.05)]; RCVD_IN_DNSWL_NONE(0.00)[e.2.4.0.0.0.0.0.0.0.0.0.0.0.0.0.0.2.0.0.4.6.8.4.0.5.4.1.0.0.a.2.list.dnswl.org : 127.0.5.0]; RCVD_TLS_ALL(0.00)[] X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 28 Nov 2019 08:48:06 -0000 On 27.11.2019 21:33, Alan Cox wrote: > Author: alc > Date: Wed Nov 27 20:33:49 2019 > New Revision: 355145 > URL: https://svnweb.freebsd.org/changeset/base/355145 > > Log: > There is no reason why we need to pin the underlying thread to its current > processor in pmap_invalidate_{all,page,range}(). These functions are using > an instruction that broadcasts the TLB invalidation to every processor, so > even if a thread migrates in the middle of one of these functions every > processor will still perform the required TLB invalidations. I think this is not the right assumption. The problem is not in TLB operations themselves, but in following 'dsb' and / or 'isb'. 'dsb' ensures that all TLB operation transmitted by the local CPU is performed and visible to other observers. But it does nothing with TLBs emitted by other CPUs. For example, if a given thread is rescheduled after all TLB operations but before 'dsb' or 'isb' is performed, then the requested synchronization does not occur at all. Michal > > Reviewed by: andrew, markj > MFC after: 10 days > Differential Revision: https://reviews.freebsd.org/D22502 > > Modified: > head/sys/arm64/arm64/pmap.c > > Modified: head/sys/arm64/arm64/pmap.c > ============================================================================== > --- head/sys/arm64/arm64/pmap.c Wed Nov 27 20:32:53 2019 (r355144) > +++ head/sys/arm64/arm64/pmap.c Wed Nov 27 20:33:49 2019 (r355145) > @@ -1043,7 +1043,6 @@ pmap_invalidate_page(pmap_t pmap, vm_offset_t va) > { > uint64_t r; > > - sched_pin(); > dsb(ishst); > if (pmap == kernel_pmap) { > r = atop(va); > @@ -1054,11 +1053,10 @@ pmap_invalidate_page(pmap_t pmap, vm_offset_t va) > } > dsb(ish); > isb(); > - sched_unpin(); > } > > static __inline void > -pmap_invalidate_range_nopin(pmap_t pmap, vm_offset_t sva, vm_offset_t eva) > +pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva) > { > uint64_t end, r, start; > > @@ -1080,20 +1078,10 @@ pmap_invalidate_range_nopin(pmap_t pmap, vm_offset_t s > } > > static __inline void > -pmap_invalidate_range(pmap_t pmap, vm_offset_t sva, vm_offset_t eva) > -{ > - > - sched_pin(); > - pmap_invalidate_range_nopin(pmap, sva, eva); > - sched_unpin(); > -} > - > -static __inline void > pmap_invalidate_all(pmap_t pmap) > { > uint64_t r; > > - sched_pin(); > dsb(ishst); > if (pmap == kernel_pmap) { > __asm __volatile("tlbi vmalle1is"); > @@ -1103,7 +1091,6 @@ pmap_invalidate_all(pmap_t pmap) > } > dsb(ish); > isb(); > - sched_unpin(); > } > > /* > @@ -3114,7 +3101,7 @@ pmap_update_entry(pmap_t pmap, pd_entry_t *pte, pd_ent > * lookup the physical address. > */ > pmap_clear_bits(pte, ATTR_DESCR_VALID); > - pmap_invalidate_range_nopin(pmap, va, va + size); > + pmap_invalidate_range(pmap, va, va + size); > > /* Create the new mapping */ > pmap_store(pte, newpte); >