Date: Wed, 29 May 2024 16:57:43 +0000 From: bugzilla-noreply@freebsd.org To: riscv@FreeBSD.org Subject: [Bug 279383] riscv bounce_bus_dmamap_load_buffer() Message-ID: <bug-279383-40250@https.bugs.freebsd.org/bugzilla/>
next in thread | raw e-mail | index | archive | help
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D279383 Bug ID: 279383 Summary: riscv bounce_bus_dmamap_load_buffer() Product: Base System Version: CURRENT Hardware: Any OS: Any Status: New Severity: Affects Only Me Priority: --- Component: riscv Assignee: riscv@FreeBSD.org Reporter: rtm@lcs.mit.edu I use an old riscv simulator whose virtio block device doesn't support the VIRTIO_BLK_F_SEG_MAX feature, so FreeBSD's vtblk_maximum_segments() decides it supports only three segments. This has worked, but stopped working after a recent update to the riscv busdma_bounce.c. The very first read of a virtio block device is 20 bytes (to read the label?). The riscv bounce_bus_dmamap_load_buffer() decides a bounce page is needed. But it rounds up the size from buflen=3D20 bytes to a whole page (since dmat->common.alignment is 4096): sgsize =3D MIN(buflen, PAGE_SIZE - (curaddr & PAGE_MASK)); if (((dmat->bounce_flags & BF_COULD_BOUNCE) !=3D 0) && map->pagesneeded !=3D 0 && addr_needs_bounce(dmat, curaddr)) { sgsize =3D roundup2(sgsize, dmat->common.alignment); curaddr =3D add_bounce_page(dmat, map, kvaddr, cura= ddr, sgsize); The immediate problem is that later the=20 buflen -=3D sgsize; wraps (since buflen is 20 and sgsize is 4096), so that buflen is huge and the while loop incorrectly makes a second iteration.=20 A potential fix is to restore the bounce_bus_dmamap_load_buffer() code from a few months ago that limits sgsize to be no more than buflen. FreeBSD 15.0-CURRENT FreeBSD 15.0-CURRENT #312 main-n250991-01d33dbbb3f8-dirty: Wed May 29 12:49:02 EDT 2024=20=20=20=20 rtm@zika:/usr/obj/usr/rtm/symbsd/src/riscv.riscv64/sys/RTM riscv --=20 You are receiving this mail because: You are the assignee for the bug.=
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?bug-279383-40250>