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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2A6E3C10F1A for ; Wed, 8 May 2024 02:34:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 788576B0083; Tue, 7 May 2024 22:34:08 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7396C6B0085; Tue, 7 May 2024 22:34:08 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6264A6B0088; Tue, 7 May 2024 22:34:08 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 450146B0083 for ; Tue, 7 May 2024 22:34:08 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id B217F160C6F for ; Wed, 8 May 2024 02:34:07 +0000 (UTC) X-FDA: 82093658934.21.12092B4 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf07.hostedemail.com (Postfix) with ESMTP id EE66340015 for ; Wed, 8 May 2024 02:34:05 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=none; spf=pass (imf07.hostedemail.com: domain of "SRS0=lPt4=ML=goodmis.org=rostedt@kernel.org" designates 139.178.84.217 as permitted sender) smtp.mailfrom="SRS0=lPt4=ML=goodmis.org=rostedt@kernel.org"; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1715135646; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=0iuBlgr0tCgQeORWxOjmhj/uy7hu26Z6cbXw4AUTKMI=; b=fFBit9oJ7rJNbY11ybCrHTgt4+oi+emzpLZg0glVGa1d2kd7NHcMMJD78FNuHMGG75ygLn D9aUdX+MZ4RjpvNMpxbGqBa7MYF74VOc8odAG4Phu9zq8lDeqCl2ruoC+AE7Y3Wl6EsNrP 96XXV0xjCOov+4LwXsO+s2yduIlKNnY= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1715135646; a=rsa-sha256; cv=none; b=UGY9MOl4F447PMdNryoRl3nTXKfgrB83moKjhaicrvbpBK8RLqrUwG2g7Ysoc3ktetBClt sMyKvxOJB+go3PTl1DGIptK31CF8CPIPZ2STenBe1jRwqXdjmbXO2zsDUFoLGiiZmzlDPg Y4T3B6Kf/MUhKVzNpg7MqqSb9xEx9AI= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=none; spf=pass (imf07.hostedemail.com: domain of "SRS0=lPt4=ML=goodmis.org=rostedt@kernel.org" designates 139.178.84.217 as permitted sender) smtp.mailfrom="SRS0=lPt4=ML=goodmis.org=rostedt@kernel.org"; dmarc=none Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id F35FF61A51; Wed, 8 May 2024 02:34:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5434DC2BBFC; Wed, 8 May 2024 02:34:04 +0000 (UTC) Date: Tue, 7 May 2024 22:34:02 -0400 From: Steven Rostedt To: Vincent Donnefort Cc: mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, mathieu.desnoyers@efficios.com, kernel-team@android.com, rdunlap@infradead.org, rppt@kernel.org, david@redhat.com, linux-mm@kvack.org Subject: Re: [PATCH v22 2/5] ring-buffer: Introducing ring-buffer mapping functions Message-ID: <20240507223402.206d6ddc@rorschach.local.home> In-Reply-To: <20240430111354.637356-3-vdonnefort@google.com> References: <20240430111354.637356-1-vdonnefort@google.com> <20240430111354.637356-3-vdonnefort@google.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: EE66340015 X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: btn7brw4auqpmmi8bed53jp8j9ue1cj6 X-HE-Tag: 1715135645-70688 X-HE-Meta: U2FsdGVkX1/EBZrgHiLL9PVptoaaeo5E0V6ZSNwnI9LbaDsbTXp3ObNcFap8RiHrlHwdpcSf14f3Zm7F2VMVI//1yjhFZdXnfweWpJNjNi+M9u97VJFodbmLmJBbuexb7blY6wV5snp7kZdmgRWpA5h3qH4bTpUigT+U8GCE2DsrVSUkM5VbW+iDZCrgQQyaKGnsTRAdezL+Obi+jp3McvQlkROMVWAJFYtec0BIRFZRTUga6nHaa7Sk5zp+G98ShIDv/Y4NPVNrQV30KViHqh8+fedjQh3LqmP8EvfC+JEuKP6mISWo4HFshNhNOcpAvmntHuOCcRzYQKC4llCwHA3wEH4p168f23g5cO2Nw1qaySuDVy7uvVqli/MbUvrng2Ll9eC9INE1L/Ph2KeL7ZSMoeDAIPAXqzECNJHgVYGAokmfhEJg8rb/G4JCimKkaIRO1PKJTZid9g+wVUQFaz8p8SLO04UuieUWCDwMBUqLjuCVx0+ZgR/y4JwB7Qc5BNF6gJ/UKjk/QI2ulgeJwtBaFRIBXQDNYX+sNvZE80juLkrRfdSc1a7vcaE9PBmI6sCFyWjS0tU6D27vzXziwMFIvqtuovbXBqLR49igATfl0VnirZrRcyNWYnO3HE5EIZMfu3lWLgNFnc0KYK8aeSAQBgNjJaXCc6lwXkFOAyvQ5/NEP0NzE3UMjLGKVZjEXEZ0FhaxvOgJxNpN9/PwyhHEoBj24TPe8CK5iD9nVixubznt1wOCXNIG1ex1zzTu5OA6Q7LeyGwu50P22rgDSehst/P/TlITqOOqlBAXfxDiYI3TE3FuyIOeL+KwA/AdK4DmzRbvRfuGuLei+DQMwK5QH2fqH9AM09FmEgJjEHNx71V+3jeVjPKEE+sb6yktA2ePNUNYBVHS5f39muAshMYaE7ROzID52rYspWTThbJ81ONCoI8RS57XyMcgYIRIIeHUfvxVAEgNTCpnfX2 EdXXqlXy YabBKmOcmfDYRxgA8BIt6IFm+PZJa6uMPjIyCZ+1zQED1bvjIKg3TElu+B8fUHu+nAUdCYgxEt6Te9u0o92SwpSBvpgyGgtVbs/6sjbjHNUANNj5aAa2e/cvlCH2IMuyhOl9DtuDGD/r0Tnu9U/ebodS7VNP12DlNLBCko4cLGQgIqwsVT7FXlyPr3ioReDVWpSTXrkO2sLqJhPXyBfKSWzz62WXVfuSkKjG5FzWW9yZm7hJW55KFt6D6YiOlCk7WXk9JnnZsDBRNYCG6kwbKZ/SJ0w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 30 Apr 2024 12:13:51 +0100 Vincent Donnefort wrote: > +#ifdef CONFIG_MMU > +static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer, > + struct vm_area_struct *vma) > +{ > + unsigned long nr_subbufs, nr_pages, vma_pages, pgoff = vma->vm_pgoff; > + unsigned int subbuf_pages, subbuf_order; > + struct page **pages; > + int p = 0, s = 0; > + int err; > + > + /* Refuse MP_PRIVATE or writable mappings */ > + if (vma->vm_flags & VM_WRITE || vma->vm_flags & VM_EXEC || > + !(vma->vm_flags & VM_MAYSHARE)) > + return -EPERM; > + > + /* > + * Make sure the mapping cannot become writable later. Also tell the VM > + * to not touch these pages (VM_DONTCOPY | VM_DONTEXPAND). Finally, > + * prevent migration, GUP and dump (VM_IO). > + */ > + vm_flags_mod(vma, VM_DONTCOPY | VM_DONTEXPAND | VM_IO, VM_MAYWRITE); Do we really need the VM_IO? When testing this in gdb, I would get: (gdb) p tmap->map->subbuf_size Cannot access memory at address 0x7ffff7fc2008 It appears that you can't ptrace IO memory. When I removed that flag, gdb has no problem reading that memory. I think we should drop that flag. Can you send a v23 with that removed, Shuah's update, and also the change below: > + > + lockdep_assert_held(&cpu_buffer->mapping_lock); > + > + subbuf_order = cpu_buffer->buffer->subbuf_order; > + subbuf_pages = 1 << subbuf_order; > + > + nr_subbufs = cpu_buffer->nr_pages + 1; /* + reader-subbuf */ > + nr_pages = ((nr_subbufs) << subbuf_order) - pgoff + 1; /* + meta-page */ > + > + vma_pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT; > + if (!vma_pages || vma_pages > nr_pages) > + return -EINVAL; > + > + nr_pages = vma_pages; > + > + pages = kcalloc(nr_pages, sizeof(*pages), GFP_KERNEL); > + if (!pages) > + return -ENOMEM; > + > + if (!pgoff) { > + pages[p++] = virt_to_page(cpu_buffer->meta_page); > + > + /* > + * TODO: Align sub-buffers on their size, once > + * vm_insert_pages() supports the zero-page. > + */ > + } else { > + /* Skip the meta-page */ > + pgoff--; > + > + if (pgoff % subbuf_pages) { > + err = -EINVAL; > + goto out; > + } > + > + s += pgoff / subbuf_pages; > + } > + > + while (s < nr_subbufs && p < nr_pages) { > + struct page *page = virt_to_page(cpu_buffer->subbuf_ids[s]); > + int off = 0; > + > + for (; off < (1 << (subbuf_order)); off++, page++) { > + if (p >= nr_pages) > + break; > + > + pages[p++] = page; > + } > + s++; > + } The above can be made to: while (p < nr_pages) { struct page *page; int off = 0; if (WARN_ON_ONCE(s >= nr_subbufs)) break; page = virt_to_page(cpu_buffer->subbuf_ids[s]); for (; off < (1 << (subbuf_order)); off++, page++) { if (p >= nr_pages) break; pages[p++] = page; } s++; } Thanks. -- Steve > + > + err = vm_insert_pages(vma, vma->vm_start, pages, &nr_pages); > + > +out: > + kfree(pages); > + > + return err; > +} > +#else > +static int __rb_map_vma(struct ring_buffer_per_cpu *cpu_buffer, > + struct vm_area_struct *vma) > +{ > + return -EOPNOTSUPP; > +} > +#endif