April 2016 - SeaBIOS - mail.coreboot.org

Re: [SeaBIOS] virtio-blk ... block size 4096 is unsupported
by Kevin Wolf April 6, 2016

April 6, 2016

Am 05.04.2016 um 20:24 hat James Shimer geschrieben: > Thanks for the responses. What you've both said makes total sense. > We've tried 512 logical/ 4k physical and it works fine with Seabios. > Thanks Laszlo for the OVMF tip, that's totally the route we need to > take. In practice, I don't think there is a big difference for disk accesses between using 4k logical (with OVMF) and using 512b logical (with either SeaBIOS or OVMF). So if you just want to access your data optimally in the guest and don't care if it really looks like 4kn there, using a 512e setup with SeaBIOS is probably completely fine. It is very likely that your OS is already using 4k aligned requests because it knows the physical sector size, and apart from that both the file system block size and the page size aren't smaller than 4k either. So while the emulation of 512b sectors costs some performance (it is done by qemu in this configuration), it should really only kick in for the boot loader and everything else should be using correctly aligned requests without any need for emulation. Kevin > ________________________________________ > From: Laszlo Ersek <lersek(a)redhat.com> > Sent: Tuesday, April 5, 2016 12:49 PM > To: Kevin O'Connor > Cc: James Shimer; Kevin Wolf; seabios(a)seabios.org > Subject: Re: [SeaBIOS] virtio-blk ... block size 4096 is unsupported > > On 04/05/16 18:36, Kevin O'Connor wrote: > > On Tue, Apr 05, 2016 at 02:31:53PM +0200, Laszlo Ersek wrote: > >> On 04/05/16 06:25, James Shimer wrote: > >>> I've been doing some testing if KVM with 4K physical sector virtio > >>> disks and they work with KVM as a none boot disk. We'd like to be > >>> able to boot a 4k physical sector disk in KVM, is there 4K support in > >>> any seabios newer/upcoming releases, or is there a way to configure > >>> for 4k sectors? > >>> > >>> reference from master > >>> src/hw/virtio-blk.c lin 142 > >>> > >>> if (vdrive->drive.blksize != DISK_SECTOR_SIZE) { > >>> dprintf(1, "virtio-blk %pP block size %d is unsupported\n", > >>> pci, vdrive->drive.blksize); > >>> goto fail; > >>> } > >> > >> This code dates back to 4030db0d2c5a7. > >> > >> I'm not an expert, but I think BIOS interfaces don't support a sector > >> size different from 512 B. It seems that a drive with 4096 B physical > >> sectors should enable (the emulation of) a 512 B logical sector size, so > >> that it can work with code that assumes an 512 B sector size. > >> > >> https://en.wikipedia.org/wiki/Advanced_Format#512e > > > > The EDD standard ( https://en.wikipedia.org/wiki/Enhanced_Disk_Drive ) > > allows for 4K blocks. However, the older BIOS interface (eg, int > > 1301) only support 512 byte sectors. This means that the BIOS would > > need to emulate 512 byte reads should one of the older interfaces be > > called on one of these drives. This isn't difficult as SeaBIOS > > already does this for cdroms. > > That sounds great, thanks. I should have thought of CD-ROMs, I guess. > > > > >> I guess for a virtio-blk disk, that means: > >> > >> -device virtio-blk-pci,physical_block_size=4096,logical_block_size=512 > > > > In practice, almost all real drives seem to do the above. So, adding > > support for drives that don't has not previously been a priority. > > Right, I missed that 512e could be implemented in SeaBIOS itself (and I > completely missed that it had been, for CD-ROMs). > > Thanks! > Laszlo

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Re: [SeaBIOS] virtio-blk ... block size 4096 is unsupported
by Laszlo Ersek April 5, 2016

April 5, 2016

On 04/05/16 06:25, James Shimer wrote: > > Hi, > > I've been doing some testing if KVM with 4K physical sector virtio > disks and they work with KVM as a none boot disk. We'd like to be > able to boot a 4k physical sector disk in KVM, is there 4K support in > any seabios newer/upcoming releases, or is there a way to configure > for 4k sectors? > > reference from master > src/hw/virtio-blk.c lin 142 > > if (vdrive->drive.blksize != DISK_SECTOR_SIZE) { > dprintf(1, "virtio-blk %pP block size %d is unsupported\n", > pci, vdrive->drive.blksize); > goto fail; > } This code dates back to 4030db0d2c5a7. I'm not an expert, but I think BIOS interfaces don't support a sector size different from 512 B. It seems that a drive with 4096 B physical sectors should enable (the emulation of) a 512 B logical sector size, so that it can work with code that assumes an 512 B sector size. https://en.wikipedia.org/wiki/Advanced_Format#512e I guess for a virtio-blk disk, that means: -device virtio-blk-pci,physical_block_size=4096,logical_block_size=512 If your virtio disk is "4K native": https://en.wikipedia.org/wiki/Advanced_Format#4K_native (which I think corresponds to the following QEMU command line option (based on advice I had received earlier from Kevin Wolf): -device virtio-blk-pci,physical_block_size=4096,\ logical_block_size=4096,\ min_io_size=4096 ) then I believe BIOS interfaces / booting might not support the disk, by design, at all. And for that reason, I'll make an exception, and "peddle" OVMF (sorry -- I feel bad about doing this on the SeaBIOS list). UEFI (and GPT) support "4K native" by design, and OVMF supports it for virtio-blk devices. (OVMF also supports 512e.) I suggest that you repeat your test with a guest OS that you install afresh on top of OVMF. You can find pre-built OVMF binaries (RPMs) at <https://www.kraxel.org/repos/>. I recommend using them with libvirt: <https://fedoraproject.org/wiki/Using_UEFI_with_QEMU#Install_a_Fedora_VM_wit…>. If you have questions about OVMF, please let's continue on edk2-devel, to keep the noise down on the SeaBIOS list. (Note: you will have to subscribe to edk2-devel first, before you can post. Please see <https://lists.01.org/mailman/listinfo/edk2-devel>.) Thanks Laszlo

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Re: [SeaBIOS] virtio-blk ... block size 4096 is unsupported
by James Shimer April 5, 2016

April 5, 2016

After thinking about this some more, I'm not sure there is anything that can be done due to the fact that boot is using interfaces that assume 512 byte sectors such as a read sectors 13h. Is that why BIOS/boot is stuck, changing the read to allow 4k sector size could cause buffer over run because the 13h interface doesn't specify the sector size? ________________________________________ From: SeaBIOS <seabios-bounces(a)seabios.org> on behalf of James Shimer <JamesShimer(a)msn.com> Sent: Tuesday, April 5, 2016 12:25 AM To: seabios(a)seabios.org Subject: [SeaBIOS] virtio-blk ... block size 4096 is unsupported Hi, I've been doing some testing if KVM with 4K physical sector virtio disks and they work with KVM as a none boot disk. We'd like to be able to boot a 4k physical sector disk in KVM, is there 4K support in any seabios newer/upcoming releases, or is there a way to configure for 4k sectors? reference from master src/hw/virtio-blk.c lin 142 if (vdrive->drive.blksize != DISK_SECTOR_SIZE) { dprintf(1, "virtio-blk %pP block size %d is unsupported\n", pci, vdrive->drive.blksize); goto fail; } Thanks, Jim _______________________________________________ SeaBIOS mailing list SeaBIOS(a)seabios.org https://www.coreboot.org/mailman/listinfo/seabios

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virtio-blk ... block size 4096 is unsupported
by James Shimer April 5, 2016

April 5, 2016

Hi, I've been doing some testing if KVM with 4K physical sector virtio disks and they work with KVM as a none boot disk. We'd like to be able to boot a 4k physical sector disk in KVM, is there 4K support in any seabios newer/upcoming releases, or is there a way to configure for 4k sectors? reference from master src/hw/virtio-blk.c lin 142 if (vdrive->drive.blksize != DISK_SECTOR_SIZE) { dprintf(1, "virtio-blk %pP block size %d is unsupported\n", pci, vdrive->drive.blksize); goto fail; } Thanks, Jim

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Re: [SeaBIOS] Build failed in Jenkins: seabios #220
by Kevin O'Connor April 1, 2016

April 1, 2016

On Wed, Mar 30, 2016 at 07:50:33PM +0200, Jenkins Build Host wrote: > See <http://jenkins.xeni.kraxel.org:8080/job/seabios/220/changes> > > Changes: > > [kevin] Support for booting from LSI Logic LSI53C1030, SAS1068, SAS1068e [...] > Compile checking out/src/hw/mpt-scsi.o > src/hw/mpt-scsi.c: In function 'init_mpt_scsi': > src/hw/mpt-scsi.c:281:5: error: 'for' loop initial declarations are only allowed in C99 mode > for (int i = 0; i < 7; i++) > ^ > src/hw/mpt-scsi.c:281:5: note: use option -std=c99 or -std=gnu99 to compile your code > make: *** [out/src/hw/mpt-scsi.o] Error 1 > error: Bad exit status from /var/tmp/rpm-tmp.YLsXMX (%build) It's interesting that newer compilers accept the 'int i' declaration inside of for loops - I didn't realize that was allowed in C99. In any case, I pulled the declaration outside the loop to suppress the error, and I committed the change. -Kevin

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