Re: [Xen-devel] DMA trouble with current xen-sparse

[Daniel Veillard <veillard@xxxxxxxxxx>]

On Mon, Nov 07, 2005 at 01:51:35PM -0000, Ian Pratt wrote:
> 
> > Sure, took a bit of time to recompile the kernel (I didn't do 
> > this for years) and it crashed as expected, here are the info:
> > 
> >   ptr: f160ed8e 1514
> > 
> > the size looks a full ethernet frame, i.e. 1500 of payload, 2 
> > ethernet addresses and the 2bytes for the ethernet type, that 
> > looks kosher to me but clearly it is not aligned.
> 
> This allocation isn't aligned to the next power of 2 boundary ---
> usually 1514 byte allocations are 2KB aligned. 
> 
> You're not enabling some experimental option in your config that changes
> the alignment of slab allocations are you?

  Hi Ian,

sorry for not responding to your previous message. The point is that I don't
really know offhand myself those kernel internals aspects. Steven can certainly
provide a more informed answer. I checked our kernel config, and I see

  CONFIG_DEBUG_SLAB=y

to be set up in our kernel-2.6.12-i686-hypervisor.config. Browsing to check
all the other DEBUG option which might be potentially relevant I only found
CONFIG_DEBUG_KERNEL CONFIG_DEBUG_HIGHMEM and CONFIG_DEBUG_INFO enabled.
CONFIG_DEBUG_DRIVER is not set. The Xen options are:

CONFIG_XEN=y
CONFIG_ARCH_XEN=y
CONFIG_NO_IDLE_HZ=y
CONFIG_XEN_WRITABLE_PAGETABLES=y
# CONFIG_XEN_SHADOW_MODE is not set
CONFIG_XEN_SCRUB_PAGES=y
CONFIG_FOREIGN_PAGES=y
CONFIG_HAVE_ARCH_DEV_ALLOC_SKB=y
CONFIG_XEN_BLKDEV_GRANT=y
# CONFIG_XEN_BLKDEV_TAP_BE is not set
# CONFIG_XEN_BLKDEV_TAP is not set
# CONFIG_XEN_NETDEV_GRANT_TX is not set
# CONFIG_XEN_NETDEV_GRANT_RX is not set
# CONFIG_SMP_ALTERNATIVES is not set
CONFIG_X86=y
# CONFIG_X86_64 is not set
CONFIG_XENARCH="i386"
CONFIG_MMU=y
CONFIG_UID16=y
CONFIG_GENERIC_ISA_DMA=y
# CONFIG_M686 is not set

Daniel

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