On 09/03/2021 15.05, Keqian Zhu wrote:
>
>
> On 2021/3/9 21:48, Thomas Huth wrote:
>> On 17/12/2020 02.49, Keqian Zhu wrote:
>>> The parameters start and size are transfered from QEMU memory
>>> emulation layer. It can promise that they are TARGET_PAGE_SIZE
>>> aligned. However, KVM needs they are qemu_real_page_size aligned.
>>>
>>> Though no caller breaks this aligned requirement currently, we'd
>>> better add an explicit assert to avoid future breaking.
>>>
>>> Signed-off-by: Keqian Zhu <
zhukeqian1@huawei.com>
>>> ---
>>> accel/kvm/kvm-all.c | 7 +++++++
>>> 1 file changed, 7 insertions(+)
>>>
>>> ---
>>> v2
>>> - Address Andrew's commment (Use assert instead of return err).
>>>
>>> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
>>> index f6b16a8df8..73b195cc41 100644
>>> --- a/accel/kvm/kvm-all.c
>>> +++ b/accel/kvm/kvm-all.c
>>> @@ -692,6 +692,10 @@ out:
>>> #define KVM_CLEAR_LOG_ALIGN (qemu_real_host_page_size << KVM_CLEAR_LOG_SHIFT)
>>> #define KVM_CLEAR_LOG_MASK (-KVM_CLEAR_LOG_ALIGN)
>>> +/*
>>> + * As the granule of kvm dirty log is qemu_real_host_page_size,
>>> + * @start and @size are expected and restricted to align to it.
>>> + */
>>> static int kvm_log_clear_one_slot(KVMSlot *mem, int as_id, uint64_t start,
>>> uint64_t size)
>>> {
>>> @@ -701,6 +705,9 @@ static int kvm_log_clear_one_slot(KVMSlot *mem, int as_id, uint64_t start,
>>> unsigned long *bmap_clear = NULL, psize = qemu_real_host_page_size;
>>> int ret;
>>> + /* Make sure start and size are qemu_real_host_page_size aligned */
>>> + assert(QEMU_IS_ALIGNED(start | size, psize));
>>
>> Sorry, but that was a bad idea: It triggers and kills my Centos 6 VM:
>>
>> $ qemu-system-x86_64 -accel kvm -hda ~/virt/images/centos6.qcow2 -m 1G
>> qemu-system-x86_64: ../../devel/qemu/accel/kvm/kvm-all.c:690: kvm_log_clear_one_slot: Assertion `QEMU_IS_ALIGNED(start | size, psize)' failed.
>> Aborted (core dumped)
> Hi Thomas,
>
> I think this patch is ok, maybe it trigger a potential bug?
Well, sure, there is either a bug somewhere else or in this new code. But it's certainly not normal that the assert() triggers, is it?
FWIW, here's a backtrace:
#0 0x00007ffff2c1584f in raise () at /lib64/libc.so.6
#1 0x00007ffff2bffc45 in abort () at /lib64/libc.so.6
#2 0x00007ffff2bffb19 in _nl_load_domain.cold.0 () at /lib64/libc.so.6
#3 0x00007ffff2c0de36 in .annobin_assert.c_end () at /lib64/libc.so.6
#4 0x0000555555ba25f3 in kvm_log_clear_one_slot
(size=6910080, start=0, as_id=0, mem=0x555556e1ee00)
at ../../devel/qemu/accel/kvm/kvm-all.c:691
#5 0x0000555555ba25f3 in kvm_physical_log_clear
(section=0x7fffffffd0b0, section=0x7fffffffd0b0, kml=0x555556dbaac0)
at ../../devel/qemu/accel/kvm/kvm-all.c:843
#6 0x0000555555ba25f3 in kvm_log_clear (listener=0x555556dbaac0, section=0x7fffffffd0b0)
at ../../devel/qemu/accel/kvm/kvm-all.c:1253
#7 0x0000555555b023d8 in memory_region_clear_dirty_bitmap
(mr=mr@entry=0x5555573394c0, start=start@entry=0, len=len@entry=6910080)
at ../../devel/qemu/softmmu/memory.c:2132
#8 0x0000555555b313d9 in cpu_physical_memory_snapshot_and_clear_dirty
(mr=mr@entry=0x5555573394c0, offset=offset@entry=0, length=length@entry=6910080, client=client@entry=0) at ../../devel/qemu/softmmu/physmem.c:1109
#9 0x0000555555b02483 in memory_region_snapshot_and_clear_dirty
(mr=mr@entry=0x5555573394c0, addr=addr@entry=0, size=size@entry=6910080, client=client@entry=0)
at ../../devel/qemu/softmmu/memory.c:2146
#10 0x0000555555babe99 in vga_draw_graphic (full_update=0, s=0x5555573394b0)
at ../../devel/qemu/hw/display/vga.c:1661
#11 0x0000555555babe99 in vga_update_display (opaque=0x5555573394b0)
at ../../devel/qemu/hw/display/vga.c:1784
#12 0x0000555555babe99 in vga_update_display (opaque=0x5555573394b0)
at ../../devel/qemu/hw/display/vga.c:1757
#13 0x00005555558ddd32 in graphic_hw_update (con=0x555556a11800)
at ../../devel/qemu/ui/console.c:279
#14 0x00005555558dccd2 in dpy_refresh (s=0x555556c17da0) at ../../devel/qemu/ui/console.c:1742
#15 0x00005555558dccd2 in gui_update (opaque=opaque@entry=0x555556c17da0)
at ../../devel/qemu/ui/console.c:209
#16 0x0000555555dbd520 in timerlist_run_timers (timer_list=0x555556937c50)
at ../../devel/qemu/util/qemu-timer.c:574
#17 0x0000555555dbd520 in timerlist_run_timers (timer_list=0x555556937c50)
at ../../devel/qemu/util/qemu-timer.c:499
#18 0x0000555555dbd74a in qemu_clock_run_timers (type=<optimized out>)
at ../../devel/qemu/util/qemu-timer.c:670
#19 0x0000555555dbd74a in qemu_clock_run_all_timers () at ../../devel/qemu/util/qemu-timer.c:670
Looks like something in the vga code calls this with size=6910080
and thus triggers the alignment assertion?
Thomas