On 18/04/2014 16:44, Richard Henderson wrote:
On 04/18/2014 07:00 AM, Mian M. Hamayun wrote:
Hello Peter & All,
I am trying to figure out a problem in qemu on aarch64 (with kvm enabled). I
have found this problem in many different versions of qemu
(v2.0.0-rc3/rc2/rc1/rc0, master 2d03b49), and I believe that either I am
missing something common in all of these versions or its a genuine bug in qemu
on aarch64.
The problem is triggered by virtqueue_notify() function (in virtio_ring.c) from
the guest kernel and fails in the qemu_coroutine_new() while trying to do the
swapcontext(&old_uc, &uc) (see coroutine-ucontext.c:164). The
sigsetjmp(old_env, 0) just before the swapcontext() call seems to work fine, as
it returns 0, and then we invoke the swapcontext().
The host kernel reports:
"qemu-system-aar[596]: bad frame in sys_rt_sigreturn: pc=004462e0
sp=7f8020f000" and kills the qemu process due to segmentation fault. The
pc=004462e0 is for the coroutine_trampoline() but we don't actually reach it,
when this particular crash happens.
Just to give you an idea of the code I am talking about:
$~/qemu[master]$ git blame -L 159,166 coroutine-ucontext.c
00dccaf1 (Kevin Wolf 2011-01-17 16:08:14 +0000 159) makecontext(&uc,
(void (*)(void))coroutine_trampoline,
00dccaf1 (Kevin Wolf 2011-01-17 16:08:14 +0000 160) 2,
arg.i[0], arg.i[1]);
00dccaf1 (Kevin Wolf 2011-01-17 16:08:14 +0000 161)
6ab7e546 (Peter Maydell 2013-02-20 15:21:09 +0000 162) /* swapcontext() in,
siglongjmp() back out */
6ab7e546 (Peter Maydell 2013-02-20 15:21:09 +0000 163) if
(!sigsetjmp(old_env, 0)) {
00dccaf1 (Kevin Wolf 2011-01-17 16:08:14 +0000 164)
swapcontext(&old_uc, &uc);
00dccaf1 (Kevin Wolf 2011-01-17 16:08:14 +0000 165) }
00dccaf1 (Kevin Wolf 2011-01-17 16:08:14 +0000 166) return &co->base;
My qemu configure/run commands are:
./configure --target-list=aarch64-softmmu \
--cross-prefix=aarch64-linux-gnu- \
--enable-fdt *--enable-kvm* --disable-werror \
--audio-drv-list="" --static
./qemu-system-aarch64 \
*-enable-kvm* -nographic -kernel Image \
-drive if=none,file=disk_oe64.img,id=fs \
-device virtio-blk-device,drive=fs \
-m 1024 -M virt -cpu host \
-append "earlyprintk console=ttyAMA0 mem=1024M rootwait root=/dev/vda rw
init=/bin/sh"
Any ideas/comments on how to resolve this issue?
Note that a patch has just gone into glibc to rewrite setcontext et al for
aarch64. I'd try using git glibc before looking too much deeper.
r~
It seems right to me as well, as the setcontext related bug (for
aarch64) has recently been posted/fixed in glibc:
https://sourceware.org/bugzilla/show_bug.cgi?id=16629
I have also tested the example posted at:
https://sourceware.org/bugzilla/attachment.cgi?id=7435
and I get the following output on x86_64:
start f2
start f1
finish f2
finish f1
{ss_sp: (nil), ss_flags: 2, ss_size: 0}
{ss_sp: (nil), ss_flags: 2, ss_size: 0}
and this one on AArch64:
start f2
start f1
finish f2
finish f1
{ss_sp: (nil), ss_flags: 2, ss_size: 0}
*{ss_sp: 0x7ff7e723f0, ss_flags: 0, ss_size: 8192}*
I will first look into updating my glibc for AArch64 before coming back
to qemu.
Thanks for your support,
Hamayun
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