On 2 Dec 2018, at 18:08, Kevin O'Connor
On Sat, Dec 01, 2018 at 01:46:06AM +0200, Liran Alon wrote:
On 30 Nov
2018, at 21:20, Kevin O'Connor <kevin(a)koconnor.net> wrote:
On Wed, Nov 28, 2018 at 05:50:01PM +0200, Liran Alon wrote:
From: Nikita Leshchenko
When mpt-scsi receives a SCSI message, it wraps it in a MPT request
message and writes it's address to an IO port to be added to the
This MPT request is allocated on the stack. Previous to this commit,
the request is aligned to 4 bytes. However, VirtualBox LSI53c1030
device emulation aligns the request address to 8 bytes.
Therefore, this commit change alignment of request to 8 bytes.
VirtualBox source code which handles this is at
LSILOGIC_REG_REQUEST_QUEUE handler adds the request to the
queue (pRequestQueueBase). lsilogicR3Worker() reads request from
pRequestQueueBase and aligns it to 8 bytes
(u32RequestMessageFrameDesc & ~0x07).
Thanks. Is this change done to match virtualbox, or because it fixes
some type of problem?
It can be seen from QEMU’s mptsas_mmio_write() MPI_REQUEST_POST_FIFO_OFFSET handler
that QEMU aligns this value to 4 bytes which matches current SeaBIOS code.
However QEMU only emulates LSISAS1068 and not LSILOGIC53C1030.
This mpt-scsi.c SeaBIOS driver is suppose to handle both devices.
Therefore, we thought that maybe LSILOGIC53C1030 does requires value to be aligned to 8
In contrast to LSISAS1068. Deduced from VirtualBox device emulation.
Okay, it sounds like this is premptive and is not known to fix a
I'm not sure aligned(8) actually works on stack allocations with gcc
and SeaBIOS. Last I checked, in order for gcc to do proper stack
alignment (of greater than 4) it requires the x86 C stack alignment
calling convention to be fully followed. I'm not sure that SeaBIOS
always does this.
The USB drivers (eg, src/hw/ohci.c) perform manual stack alignment,
If this isn't known to fix an actual problem and there isn't a spec
that explicitly requires 8 bytes, then I'd say it's probably not worth
Thanks for your time reviewing this. Your opinion is valuable and appreciated.