OK, I've re-read this topic. Your goal is to implement blktap on
NetBSD/Xen, right?
According to Xen wiki [1], blktap provides an interface for userland
to handle block device I/O. I guess blktap gets inter-domain, shared
ring memory from hypervisor. Dom0 userland mmaps the ring memory and
I think mmap can work as follows:
- blktap(4) allocates shared ring memory
- pud(4) is attached to a parent blktap(4)
- userland asks mmap buffer (shared ring memory)
- UVM finds a VA range, attaches pud(4) there
- touching the buffer causes fault, uvm_fault - udv_fault - pud_mmap
are called
-
On Sat, 10 Sep 2011, Masao Uebayashi wrote:
On Sat, Sep 10, 2011 at 7:24 PM, Roger Pau Monné
roger@entel.upc.edu wrote:
PUD is a framework present in NetBSD that allows to implement
character and block devices in userspace. I'm trying to implement a
blktap [1] driver purely in
On Sat, Sep 10, 2011 at 7:24 PM, Roger Pau Monné
roger@entel.upc.edu wrote:
Hello,
Thanks for the atop tip, now I'm able to pass the memory around, but
the kernel crashes shortly after reading the value from the returned
memory region:
panic: kernel diagnostic assertion
It is called pipe(2), isn't it?
Thanks for the reply, but I don't understand why pipe could be helpful
in this situation, the mmap kernel call needs to return a paddr_t (a
memory region), and pipe returns a pair of file descriptors, that I
cannot pass to the kernel. The flow of a PUD call is
On Wed, Sep 07, 2011 at 10:33:54AM +0200, Roger Pau Monné wrote:
Hello,
Since there is no mmap implementation for PUD devices I began working
on one. I would like to make an implementation that avoids copying
buffers around user-space and kernel memory, since mmap is usually
used for fast
On Wed, 7 Sep 2011, Roger Pau Monné wrote:
Basically we use pud_request to pass the request to the user-space
server, and the server returns a memory address, allocated in the
user-space memory of it's process. Then I try to read the value of the
user space memory from the kernel, which works
On 07.09.2011 10:33, Roger Pau Monné wrote:
Since there is no mmap implementation for PUD devices I began working
on one. I would like to make an implementation that avoids copying
buffers around user-space and kernel memory, since mmap is usually
used for fast applications. I began working on
