And we saw similar problems too.
In our case the problem was in large PIO transfers.
Since edk2 code base uses PIO for ATAPI devices, we are unable to handle
such reads in our VM, because we have a 1MB bounce buffer for PIO.
There were two solutions implemented:
1. We have added DMA support.
2. We have limited maximum transfer size for all block devices to 1 MB
(in ScsiDiskDxe).
//
// limit the data bytes that can be transferred by one Read(10) or
Read(16) Command
//
if (!ScsiDiskDevice->Cdb16Byte) {
- MaxBlock = 0xFFFF;
+ MaxBlock = 0x200; // 1mb
} else {
MaxBlock = 0xFFFFFFFF;
}
The second solution is not so good, and I started to think about
splitting request at
AtaAtapiPassThruDxe, before submitting it to ATA device.
Hope it helps.
On Mon, 2013-11-18 at 19:35 -0800, H. Peter Anvin wrote:
> On 11/18/2013 05:47 PM, David F. wrote:
> > Thanks - I found the grub option for set debug= (I couldn't use all
> > since it would lock up - but used disk,efidisk,modules,loader) and can
> > see it reads 0x100 sectors from sector 0x500 then reads 0x4C00 sectors
> > from sector 0x600. So perhaps that's it. Yes, legacy reads in the
> > same inirmfs.gz file (which occupies 0x5AF to 0x525C) but I'm sure it
> > does it in smaller chunks.
>
> We saw similar problems with extremely large reads while developing the
> Linux EFI boot stub. We ended up capping the size of any one read call
> to 1 MB. Sad but true.
>
> -hpa
>
>
>
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