Re: [Qemu-devel] [Question] dump memory when host pci device is used by guest

[Dave Anderson]

----- Original Message -----
> On 10/24/2011 04:25 PM, Dave Anderson wrote:
> > > The question is that: 'virsh dump' can not be used when host pci device
> > > is used by guest. We are discussing how to fix the problem. We have 
> > > determined
> > > that introduce a new monitor command dump. Jan suggested that the core 
> > > file's
> > > format is gdb standard core format. Does crash support such format?  If 
> > > no,
> > > is it possible to support such format?
> >
> > If you are talking about an ELF core dump of the user-space qemu-kvm process
> > running on the host, then it's certainly not supported.
> 
> No, an ELF image of the guest's physical memory.

Well then that should be pretty straight forward to support.  Depending upon
how similar it would be to the "standard" kdump ELF format, the only other
issue is how to determine the physical base address at which the kernel is
loaded, in order to be able to translate the mapped kernel-text/static-data
virtual region of the x86_64 arch (the __START_KERNEL_map region).
 
> > As to whether it's possible, I suppose it could be done if a 
> > phyical-memory-read
> > function could be created for it, similar to what I asked about for live 
> > analysis
> > of a guest kernel run on/from the KVM host.
> 
> We could use the gdb protocol for this.  Currently it reads/writes
> virtual memory, but we could extend the gdbserver command to make these
> commands apply to physical memory.