From owner-svn-src-head@freebsd.org Thu Nov 5 11:58:58 2015 Return-Path: Delivered-To: svn-src-head@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 10BC0A2544E; Thu, 5 Nov 2015 11:58:58 +0000 (UTC) (envelope-from onwahe@gmail.com) Received: from mail-io0-x232.google.com (mail-io0-x232.google.com [IPv6:2607:f8b0:4001:c06::232]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id CB432118D; Thu, 5 Nov 2015 11:58:57 +0000 (UTC) (envelope-from onwahe@gmail.com) Received: by ioll68 with SMTP id l68so87827950iol.3; Thu, 05 Nov 2015 03:58:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=YtXEp8pRlq2OrhcpKgUy1zLQ/XQNMJgCK3sWkiFNFdE=; b=J1Y0mri+zCApblTsSEP7bJphF1eLYt7beTaLMOMkgc9rnJ/Hwh2flFIr7RiN1oVE9e p1E1EgyG10PUyWezsWR2JPvmNjz8KMQrcC6YTwii3hct/ChSrt9jRTpZQjZL0+RkW0RN N1Xqc9kWSwgRzRxVHHR5YN0I/eHUTNYT/wD60Rspi0809w8ArUnS/5LQL2HlPwpaBUHo ZJ6/oi6dGDA8wVcy7GH8jzOU6LMC64r88P7dx7ByXPG75oYc5eSGxNzfMCL5z9AhZR/Q I39LdopVHYDQF7gftbklPSkYAOCyG8cVBhhVj0Vdw1aHJz16YM4BmDJ9Z0bB6ozfGSiN UaEw== MIME-Version: 1.0 X-Received: by 10.107.3.79 with SMTP id 76mr9031895iod.30.1446724737301; Thu, 05 Nov 2015 03:58:57 -0800 (PST) Received: by 10.64.173.228 with HTTP; Thu, 5 Nov 2015 03:58:57 -0800 (PST) In-Reply-To: References: <201510221638.t9MGc1cc053885@repo.freebsd.org> <56348FF8.3010602@gmail.com> <1446394311.91534.236.camel@freebsd.org> Date: Thu, 5 Nov 2015 12:58:57 +0100 Message-ID: Subject: Re: svn commit: r289759 - in head/sys/arm: arm include From: Svatopluk Kraus To: Jason Harmening Cc: Ian Lepore , Ganbold Tsagaankhuu , src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Content-Type: text/plain; charset=UTF-8 X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 05 Nov 2015 11:58:58 -0000 On Thu, Nov 5, 2015 at 1:11 AM, Jason Harmening wrote: > > On Wed, Nov 4, 2015 at 2:17 PM, Svatopluk Kraus wrote: >> >> On Tue, Nov 3, 2015 at 8:45 AM, Jason Harmening >> wrote: >> > >> > On Sun, Nov 1, 2015 at 8:11 AM, Ian Lepore wrote: >> >> >> >> >> >> It's almost certainly not related to sysinit ordering. This exception >> >> is happening during mmc probing after interrupts are enabled. >> >> >> >> It appears that the problem is the faulting code is running on one of >> >> the very early pre-allocated kernel stacks (perhaps in an interrupt >> >> handler on an idle thread stack), and these stacks are not in memory >> >> represented in the vm page arrays. The mmc code is using a 64-byte >> >> buffer on the stack and mapping it for DMA. Normally that causes a >> >> bounce for cacheline alignment, but unluckily in this case that buffer >> >> on the stack just happened to be aligned to a cacheline boundary and a >> >> multiple of the cacheline size, so no bounce. That causes the new sync >> >> logic that is based on keeping vm_page_t pointers and offsets to get a >> >> NULL pointer back from PHYS_TO_VM_PAGE when mapping, then it dies at >> >> sync time trying to dereference that. It used to work because the sync >> >> logic used to use the vaddr, not a page pointer. >> >> >> >> Michal was working on a patch yesterday. >> >> >> > >> > Ah, thanks for pointing that out Ian. I was left scratching my head >> > (admittedly on the road and w/o easy access to the code) wondering what >> > on >> > earth would be trying to do DMA during SI_SUB_CPU. >> > >> >> >> Using of fictitious pages is not so easy here as in case pointed by >> kib@ where they are allocated and freed inside one function. For sync >> list sake, they must be allocated when a buffer is loaded and freed >> when is unloaded. >> >> Michal uses pmap_kextract() in case when KVA of buffer is not zero in >> his proof-of-concept patch: >> https://gist.github.com/strejda/d5ca3ed202427a2e0557 >> When KVA of buffer is not zero, temporary mapping is not used at all, >> so vm_page_t array is not needed too. >> >> IMO, buffer's physical address can be saved in sync list to be used >> when its KVA is not zero. Thus pmap_kextract() won't be called in >> dma_dcache_sync(). > > > I like the idea of storing off the physical address. If you want to save > space in the sync list, I think you can place busaddr and pages in a union, > using vaddr == 0 to select which field to use. Some people frown upon use > of unions, though. > > Any reason the panics on PHYS_TO_VM_PAGE in load_buffer() and load_phys() > shouldn't be KASSERTs instead? KASSERTs are fine. I have looked at Michal's patch again and only KASSERT should be in load_phys() as such buffers are unmapped, temporary mapping must be used and so, they must be in vm_page_array. And maybe some inline function for getting PA from sync list would be nice too. I would like to review final patch if you are going to make it. And it would be nice if Ganbold will test it. Phabricator?