Date: Wed, 29 Apr 2015 16:20:17 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: Svatopluk Kraus <onwahe@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: <20150429132017.GM2390@kib.kiev.ua> In-Reply-To: <CAFHCsPX9rgmCAPABct84a000NuBPQm5sprOAQr9BTT6Ev6KZcQ@mail.gmail.com> 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>
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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. > (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. > (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. > (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. > > Did I miss out something? > > > > -- > > John Baldwin
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