Hello Antony, On 02.03.21 15:28, Antony Pavlov wrote: > On Sun, 28 Feb 2021 20:08:36 +0100 > Ahmad Fatoum <ahmad@xxxxxx> wrote: > > Hi! > >> MMU-less MIPS doesn't play along nicely with VIRTIO_PCI. >> e.g. Reading from a virtio-rng, will return clearly bogus data. >> Document this in the Kconfig, so no one else trips over this. >> >> Eventually, this should be fixed.. > > > Please describe, how can I reproduce the problem. - Apply this series on top of next, but revert this patch - Use qemu-malta-defconfig - Built with CONFIG_HW_RANDOM_VIRTIO=y and CONFIG_VIRTIO_PCI=y - Run: qemu-system-mips -m 256M -device VGA -M malta -serial stdio -monitor null \ -bios ./images/barebox-qemu-malta.img -device virtio-rng-pci,disable-legacy=on - Execute md -s /dev/hwrng0 three times: barebox@qemu malta:/ md -s /dev/hwrng0 00000000: 0000e632 0000000d 81ff8410 00000000 ...2............ 00000010: 0000e632 0000000d 81ff8410 00000000 ...2............ 00000020: 0000e632 0000000d 81ff8410 00000000 ...2............ 00000030: 0000e632 0000000d 81ff8410 00000000 ...2............ 00000040: 0000e632 0000000d 81ff8410 00000000 ...2............ 00000050: 0000e632 0000000d 81ff8410 00000000 ...2............ 00000060: 0000e632 0000000d 81ff8410 00000000 ...2............ 00000070: 0000e632 0000000d 81ff8410 00000000 ...2............ 00000080: 0000e632 0000000d 81ff8410 00000000 ...2............ 00000090: 0000e632 0000000d 81ff8410 00000000 ...2............ 000000a0: 0000e632 0000000d 81ff8410 00000000 ...2............ 000000b0: 0000e632 0000000d 81ff8410 00000000 ...2............ 000000c0: 0000e632 0000000d 81ff8410 00000000 ...2............ 000000d0: 0000e632 0000000d 81ff8410 00000000 ...2............ 000000e0: 0000e632 0000000d 81ff8410 00000000 ...2............ 000000f0: 0000e632 0000000d 81ff8410 00000000 ...2............ barebox@qemu malta:/ md -s /dev/hwrng0 00000000: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 00000010: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 00000020: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 00000030: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 00000040: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 00000050: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 00000060: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 00000070: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 00000080: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 00000090: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 000000a0: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 000000b0: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 000000c0: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 000000d0: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 000000e0: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 000000f0: 30303030 30306630 3a203030 30306536 000000f0: 0000e6 barebox@qemu malta:/ md -s /dev/hwrng0 00000000: 30303030 30306630 3a203330 33303330 000000f0: 303030 00000010: 30303030 30306630 3a203330 33303330 000000f0: 303030 00000020: 30303030 30306630 3a203330 33303330 000000f0: 303030 00000030: 30303030 30306630 3a203330 33303330 000000f0: 303030 00000040: 30303030 30306630 3a203330 33303330 000000f0: 303030 00000050: 30303030 30306630 3a203330 33303330 000000f0: 303030 00000060: 30303030 30306630 3a203330 33303330 000000f0: 303030 00000070: 30303030 30306630 3a203330 33303330 000000f0: 303030 00000080: 30303030 30306630 3a203330 33303330 000000f0: 303030 00000090: 30303030 30306630 3a203330 33303330 000000f0: 303030 000000a0: 30303030 30306630 3a203330 33303330 000000f0: 303030 000000b0: 30303030 30306630 3a203330 33303330 000000f0: 303030 000000c0: 30303030 30306630 3a203330 33303330 000000f0: 303030 000000d0: 30303030 30306630 3a203330 33303330 000000f0: 303030 000000e0: 30303030 30306630 3a203330 33303330 000000f0: 303030 000000f0: 30303030 30306630 3a203330 33303330 000000f0: 303030 Something is clearly wrong here, but I didn't look further. If you repeat the same steps but with CONFIG_MMU=y, you will see random data as expected (You can cp /dev/hwrng0 /dev/fb0 to see for yourself that there is no obvious pattern, unlike with MMU=n). Cheers, Ahmad > > >> >> Signed-off-by: Ahmad Fatoum <ahmad@xxxxxx> >> --- >> drivers/virtio/Kconfig | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/drivers/virtio/Kconfig b/drivers/virtio/Kconfig >> index ecf66987b3ed..91a89d3e1b89 100644 >> --- a/drivers/virtio/Kconfig >> +++ b/drivers/virtio/Kconfig >> @@ -28,6 +28,7 @@ config VIRTIO_MMIO >> config VIRTIO_PCI >> tristate "PCI driver for virtio devices" >> depends on PCI && HAS_DMA >> + depends on MMU && MIPS || !MIPS >> select VIRTIO >> help >> This driver provides support for virtio based paravirtual device >> -- >> 2.30.0 >> >> >> _______________________________________________ >> barebox mailing list >> barebox@xxxxxxxxxxxxxxxxxxx >> http://lists.infradead.org/mailman/listinfo/barebox > > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
