On 29.07.14 00:33, Scott Wood wrote:
On Mon, 2014-07-28 at 16:04 +0200, Alexander Graf wrote:
On 11.07.14 10:39, Bharat Bhushan wrote:
This patch emulates debug registers and debug exception
to support guest using debug resource. This enables running
gdb/kgdb etc in guest.
On BOOKE architecture we cannot share debug resources between QEMU and
guest because:
When QEMU is using debug resources then debug exception must
be always enabled. To achieve this we set MSR_DE and also set
MSRP_DEP so guest cannot change MSR_DE.
When emulating debug resource for guest we want guest
to control MSR_DE (enable/disable debug interrupt on need).
So above mentioned two configuration cannot be supported
at the same time. So the result is that we cannot share
debug resources between QEMU and Guest on BOOKE architecture.
In the current design QEMU gets priority over guest, this means that if
QEMU is using debug resources then guest cannot use them and if guest is
using debug resource then QEMU can overwrite them.
Signed-off-by: Bharat Bhushan <bharat.bhus...@freescale.com>
---
Hi Alex,
I thought of having some print in register emulation if QEMU
is using debug resource, Also when QEMU overwrites guest written
values but that looks excessive. If I uses some variable which
get set when guest starts using debug registers and check in
debug set ioctl then that look ugly. Looking for suggestions
Whatever you do, have QEMU do the print, not the kernel.
How would that be accomplished? How would the kernel know to exit to
QEMU, and how would the exit reason be conveyed?
QEMU is the one forcefully enabling debug and overwriting guest debug
registers, so it also knows when it did overwrite valid ones.
Alex
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