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From: Blue Swirl <blauwirbel@gmail.com>
Date: Mon, 14 Sep 2009 18:49:21 +0300
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Subject: [Qemu-devel] Re: sparc esp NetBSD-guest "sd3: mode sense (4)
	returned nonsense"
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To: Artyom Tarasenko <atar4qemu@googlemail.com>
Cc: qemu-devel <qemu-devel@nongnu.org>

On Mon, Sep 14, 2009 at 12:32 AM, Artyom Tarasenko
<atar4qemu@googlemail.com> wrote:
> From NetBSD source, it looks like HDD geometry detection should work
> under qemu: they call "mode sense" and "read capacity", and both
> commands are implemented in qemu's hw/scsi-disk.h. It doesn't work
> though, so NetBSD has to fabricate a disk geometry.
>
> To make debugging easier I tried to boot an older version - NetBSD
> 1.3.3. And put some extra debugging in esp.c:
>
> static uint32_t get_cmd(ESPState *s, uint8_t *buf)
> {
> =C2=A0 =C2=A0uint32_t dmalen;
> =C2=A0 =C2=A0int target;
>
> =C2=A0 =C2=A0target =3D s->wregs[ESP_WBUSID] & BUSID_DID;
> =C2=A0 =C2=A0if (s->dma) {
> =C2=A0 =C2=A0 =C2=A0 =C2=A0dmalen =3D s->rregs[ESP_TCLO] | (s->rregs[ESP_=
TCMID] << 8);
> =C2=A0 =C2=A0 =C2=A0 =C2=A0s->dma_memory_read(s->dma_opaque, buf, dmalen)=
;
> =C2=A0 =C2=A0} else {
> =C2=A0 =C2=A0 =C2=A0 =C2=A0dmalen =3D s->ti_size;
> =C2=A0 =C2=A0 =C2=A0 =C2=A0memcpy(buf, s->ti_buf, dmalen);
> printf("NON-DMA rptr %d, wptr %d %2x (0) %2x %2x %2x %2x\n",
> s->ti_rptr, s-> ti_wptr, buf[0],buf[1], buf[2],buf[3], buf[4]);
> =C2=A0 =C2=A0 =C2=A0 =C2=A0buf[0] =3D 0;
> =C2=A0 =C2=A0}
>
> qemu-system-sparc -M SS-20 -nographic =C2=A0-hda ~/sparc/miniroot-133.fs =
-m 64
> ...
> NON-DMA rptr 0, wptr 1 c0 (0) =C2=A00 =C2=A00 1a =C2=A00
> Set ATN & Stop: cmdlen 3
> scsi-disk: Command: lun=3D0 tag=3D0x0 data=3D0x00 0x00 0x1a 0x00 0x04 0x0=
0
> scsi-disk: Test Unit Ready
> scsi-disk: Command complete tag=3D0x0 status=3D0 sense=3D0
> sd3: mode sense (4) returned nonsense; using fictitious geometry
>
>
> NetBSD sent command "0x1a" via Set ATN & Stop, but it for some reason
> the command got padded and disk got "0x0 0x0 0x1a", no wonder that its
> output looks like a non-sense to NetBSD.
>
> Any ideas why does it happen?
>

The problem could be in the DMA (sparc32_dma.c), or incorrect
programming of DMA or IOMMU DVMA by NetBSD, (or bug in iommu.c). All
my NetBSD <4.0 boot CDs crash because of a NMI from IOMMU (DMA tries
to access a page not in IOMMU tables). The changes in NetBSD
Sparc/ESP/DMA/IOMMU code from 3.x to 4.0 could be enlightening.