On 10/02/2015 10:52 AM, Julien Grall wrote:
On 02/10/15 15:31, Julien Grall wrote:
Hi David,
On 02/10/15 15:09, David Vrabel wrote:
On 30/09/15 11:45, Julien Grall wrote:
For ARM64 guests, Linux is able to support either 64K or 4K page
granularity. Although, the hypercall interface is always based on 4K
page granularity.
With 64K page granularity, a single page will be spread over multiple
Xen frame.
To avoid splitting the page into 4K frame, take advantage of the
extent_order field to directly allocate/free chunk of the Linux page
size.
Note that PVMMU is only used for PV guest (which is x86) and the page
granularity is always 4KB. Some BUILD_BUG_ON has been added to ensure
that because the code has not been modified.
This causes a BUG() in x86 PV guests when decreasing the reservation.
Xen says:
(XEN) d0v2 Error pfn 0: rd=0 od=32753 caf=8000000000000001
taf=7400000000000001
(XEN) memory.c:250:d0v2 Bad page free for domain 0
And Linux BUGs with:
[ 82.032654] kernel BUG at
/anfs/drall/scratch/davidvr/x86/linux/drivers/xen/balloon.c:540!
Which is a non-zero return value from the decrease_reservation hypercall.
The frame_list[] has been incorrectly populated. The below patch fixes
it for me. Please test as well.
FIY, I've just tested with the patch on ARM64 and I haven't see any issue.
I had a quick one-off test and this fixes it on x86. I'll schedule it
for the overnight run too.
-boris
Sorry for the breakage, I think I haven't spot the bug on my board
because most the PV drivers are allocating one balloon page at the time
by default.
This patch looks valid to me. i was resetting and incremented for each
loop on an early version. Although I dropped it by mistake when I use a
different way to decrease the reservation.
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