Re: [Xen-users] Error accessing memory mapped by xenforeignmemory_map()

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

Adding the ARM maintainers.

On Wed, Oct 25, 2017 at 11:54:59AM -0500, Brett Stahlman wrote:
> I'm trying to use the "xenforeignmemory" library to read arbitrary
> memory ranges from a Xen domain. The code performing the reads is
> designed to run in dom0 on a Zynq ultrascale MPSoC (ARM64), though I'm
> currently testing in QEMU. I constructed a simple test program, which
> reads an arbitrary domid/address pair from the command line, converts
> the address (assumed to be physical) to a page frame number, and uses
> xenforeignmemory_map() to map the page into the test app's virtual
> memory space. Although xenforeignmemory_map() returns a non-NULL
> pointer, my attempt to dereference it fails with the following error:
> 
> (XEN) traps.c:2508:d0v1 HSR=0x93810007 pc=0x400a20 gva=0x7f965f7000
> gpa=0x00000030555000
> [   74.361735] Unhandled fault: ttbr address size fault (0x92000000)
> at 0x0000007f965f7000
> Bus error

I'm not sure what a Bus error means on ARM, have you tried to look
at traps.c:2508 to see if there's some comment explaining why this
fault is triggered?

I'm not sure the xenforeigmemory library is used on ARM, since IIRC on
x86 that's mainly used for QEMU device emulation, which is not done
for ARM. There are examples of guest memory mappings on tools/libxc/,
for example xc_dom_boot.c, although that's using the
xc_map_foreign_ranges interface.

Roger.

_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxx
https://lists.xen.org/xen-users