Date: Wed, 29 Apr 2015 17:09:18 +0200 From: Svatopluk Kraus <onwahe@gmail.com> To: Konstantin Belousov <kostikbel@gmail.com> Cc: John Baldwin <jhb@freebsd.org>, Adrian Chadd <adrian@freebsd.org>, Warner Losh <imp@bsdimp.com>, Jason Harmening <jason.harmening@gmail.com>, freebsd-arch <freebsd-arch@freebsd.org> Subject: Re: bus_dmamap_sync() for bounced client buffers from user address space Message-ID: <CAFHCsPWjEFBF%2B-7SR7EJ3UHP6oAAa9xjbu0CbRaQvd_-6gKuAQ@mail.gmail.com> In-Reply-To: <20150429132017.GM2390@kib.kiev.ua> References: <CAFHCsPXMjge84AR2cR8KXMXWP4kH2YvuV_uqtPKUvn5C3ygknw@mail.gmail.com> <38574E63-2D74-4ECB-8D68-09AC76DFB30C@bsdimp.com> <CAJ-VmomqGkEFVauya%2BrmPGcD_-=Z-mmg1RSDf1D2bT_DfwPBGA@mail.gmail.com> <1761247.Bq816CMB8v@ralph.baldwin.cx> <CAFHCsPX9rgmCAPABct84a000NuBPQm5sprOAQr9BTT6Ev6KZcQ@mail.gmail.com> <20150429132017.GM2390@kib.kiev.ua>
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On Wed, Apr 29, 2015 at 3:20 PM, Konstantin Belousov <kostikbel@gmail.com> wrote: > On Wed, Apr 29, 2015 at 12:22:19PM +0200, Svatopluk Kraus wrote: >> If using unmapped buffers is the way we will take to play with user >> space buffers, then: >> >> (1) DMA clients, which support DMA for user space buffers, must use >> some variant of _bus_dmamap_load_phys(). They must wire physical pages >> in system anyway. > No, vm_fault_quick_hold_pages() + bus_dmamap_load_ma(). > Or yes, if you count bus_dmamap_load_ma() as a variant of _load_phys(). > I do not. There are only two basic functions in MD implementations which all other functions call: _bus_dmamap_load_phys() and _bus_dmamap_load_buffer() as a synonym for unmapped buffers and mapped ones. Are you saying that bus_dmamap_load_ma() should be some third kind? > >> (2) Maybe some better way how to temporarily allocate KVA for unmapped >> buffers should be implemented. > See some other mail from me about non-blocking sfbuf allocator with > callback. This small list was meant as summary. As I saw your emails in this thread, I added this point . I did not get that it's already in source tree. > >> (3) DMA clients which already use _bus_dmamap_load_uio() with >> UIO_USERSPACE must be reimplemented or made obsolete. > Yes. > >> (4) UIO_USERSPACE must be off limit in _bus_dmamap_load_uio() and man >> page should be changed according to it. > Yes. Hmm, I think that for the beginning, _bus_dmamap_load_uio() for UIO_USERSPACE can be hacked to use bus_dmamap_load_ma(). Maybe with some warning to force users of old clients to reimplement them. > >> (5) And pmap can be deleted from struct bus_dmamap and all functions >> which use it as argument. Only kernel pmap will be used in DMA >> framework. > Probably yes. >
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