Date: Tue, 28 Apr 2015 10:19:20 -0600 From: Warner Losh <imp@bsdimp.com> To: John Baldwin <jhb@FreeBSD.org> Cc: freebsd-arch <freebsd-arch@freebsd.org>, Konstantin Belousov <kostikbel@gmail.com>, Jason Harmening <jason.harmening@gmail.com>, Svatopluk Kraus <onwahe@gmail.com> Subject: Re: bus_dmamap_sync() for bounced client buffers from user address space Message-ID: <38574E63-2D74-4ECB-8D68-09AC76DFB30C@bsdimp.com> In-Reply-To: <1876382.0PQNo3Rp24@ralph.baldwin.cx> References: <CAFHCsPXMjge84AR2cR8KXMXWP4kH2YvuV_uqtPKUvn5C3ygknw@mail.gmail.com> <553B9E64.8030907@gmail.com> <20150425163444.GL2390@kib.kiev.ua> <1876382.0PQNo3Rp24@ralph.baldwin.cx>
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[-- Attachment #1 --] > On Apr 28, 2015, at 7:40 AM, John Baldwin <jhb@FreeBSD.org> wrote: > >> I believe UIO_USERSPACE is almost unused, it might be there for some >> obscure (and buggy) driver. > > I believe it was added (and only ever used) in crypto drivers, and that they > all did bus_dma operations in the context of the thread that passed in the > uio. I definitely think it is fragile and should be replaced with something > more reliable. Fusion I/O’s SDK used this trick to allow mapping of userspace buffers down into the block layer after doing the requisite locking / pinning / etc of the buffers into memory. That’s if memory serves correctly (the SDK did these things, I can’t easily check on that detail since I’m no longer at FIO). Warner [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Comment: GPGTools - https://gpgtools.org iQIcBAEBCgAGBQJVP7MIAAoJEGwc0Sh9sBEAMb0P/2yrwv3jtTWEKkmFUBwOGOVB I1BB21SS91M/v5it92fHDQtgUgZUsDg49Ej2jYZ9Llv7LuOVr/PX/w9+F/evxFRo Vt/LSo/BXRIuuoNMc+pvMBEPL14e5WtrWXCvS4tQnfFH4mljcRqXpagrVIsHaaIC 3Gm3RwEfb+lvgNug5haryW6NaHwanhd+NMAlasemy2iAhey2ur+1qGGL3GtX5S5T 2VxO6rvVMbsaepvywTjgtGA68CE+CnCY1hMi78CIPEXeA5Kn2+Ugy6DOGDTOLa8s ABJ+2DnWjJF2bv7fxrBfiWmn9CRbqOpwaFmLG1nwM5/ZIdLJ8Q4RkAd1ynky0NXS jm2529wOmzCGmXftVffCNt83vZeVcmkaC4NLxnVx+1iDRwMlTVcWZTRwSpR3zqiE srviQE+PkCuRX8B7RwTXLwyPLIrKg78Uhn8YAhrs0MvLhvdCiS8q3CprnI37phPO 9gIBMITFYG61fjxMdOdjehpL2hRVW+nudKH8ZI1AqVqCF0wGgAQx192KpKVo0IEh g9QwXY04GS+PrqwEk1tO2st+/DYcEKDKjmz3ucAgM/GXZd8EtbxfbCWTOilrgVN5 sDoCRlFXC9tfyIYWDoa+cj8UxE7YPQbnquz+DcD0JDtHwSU6iBgd23W2Jj4/wJu5 5XcBt0cfYdpTObv74roC =FS3o -----END PGP SIGNATURE-----
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