From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [PATCH v12 09/11] pvqspinlock, x86: Add para-virtualization support Date: Tue, 25 Nov 2014 19:33:58 -0500 Message-ID: <54751FF6.5050808__32100.5312529907$1416962154$gmane$org@hp.com> References: <1413483040-58399-1-git-send-email-Waiman.Long@hp.com> <1413483040-58399-10-git-send-email-Waiman.Long@hp.com> <20141024085437.GV21513@worktop.programming.kicks-ass.net> <544E830C.6070307@hp.com> <20141027180252.GC12989@laptop.dumpdata.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1XtQYa-0007LA-2v for xen-devel@lists.xenproject.org; Wed, 26 Nov 2014 00:34:08 +0000 In-Reply-To: <20141027180252.GC12989@laptop.dumpdata.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Konrad Rzeszutek Wilk Cc: linux-arch@vger.kernel.org, Raghavendra K T , kvm@vger.kernel.org, Oleg Nesterov , Peter Zijlstra , Scott J Norton , x86@kernel.org, Paolo Bonzini , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Ingo Molnar , David Vrabel , "H. Peter Anvin" , xen-devel@lists.xenproject.org, Thomas Gleixner , "Paul E. McKenney" , Linus Torvalds , Boris Ostrovsky , Douglas Hatch List-Id: xen-devel@lists.xenproject.org On 10/27/2014 02:02 PM, Konrad Rzeszutek Wilk wrote: > On Mon, Oct 27, 2014 at 01:38:20PM -0400, Waiman Long wrote: >> >> My concern is that spin_unlock() can be called in many places, including >> loadable kernel modules. Can the paravirt_patch_ident_32() function able to >> patch all of them in reasonable time? How about a kernel module loaded later >> at run time? > It has too. When the modules are loaded the .paravirt symbols are exposed > and the module loader patches that. > > And during bootup time (before modules are loaded) it also patches everything > - when it only runs on one CPU. > I have been changing the patching code to patch the unlock call sites and it seems to be working now. However, when I manually inserted a kernel module using insmod and run the code in the newly inserted module, I got memory access violation as follows: BUG: unable to handle kernel NULL pointer dereference at (null) IP: [< (null)>] (null) PGD 18d62f3067 PUD 18d476f067 PMD 0 Oops: 0010 [#1] SMP Modules linked in: locktest(OE) ebtable_nat ebtables xt_CHECKSUM iptable_mangle bridge autofs4 8021q garp stp llc ipt_REJECT nf_conntrack_ipv4 nf_defrag_ipv4 iptable_filter ip_tables ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables ipv6 vhost_net macvtap macvlan vhost tun uinput ppdev parport_pc parport sg microcode pcspkr virtio_balloon snd_hda_codec_generic virtio_console snd_hda_intel snd_hda_controller snd_hda_codec snd_hwdep snd_seq snd_seq_device snd_pcm snd_timer snd soundcore virtio_net i2c_piix4 i2c_core ext4(E) jbd2(E) mbcache(E) floppy(E) virtio_blk(E) sr_mod(E) cdrom(E) virtio_pci(E) virtio_ring(E) virtio(E) pata_acpi(E) ata_generic(E) ata_piix(E) dm_mirror(E) dm_region_hash(E) dm_log(E) dm_mod(E) [last unloaded: speedstep_lib] CPU: 1 PID: 3907 Comm: run-locktest Tainted: G W OE 3.17.0-pvqlock #3 Hardware name: Red Hat KVM, BIOS Bochs 01/01/2011 task: ffff8818cc5baf90 ti: ffff8818b7094000 task.ti: ffff8818b7094000 RIP: 0010:[<0000000000000000>] [< (null)>] (null) RSP: 0018:ffff8818b7097db0 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 00000000004c4b40 RCX: 0000000000000000 RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff8818d3f052c0 RBP: ffff8818b7097dd8 R08: 0000000080522014 R09: 0000000000000000 R10: 0000000000001000 R11: 0000000000000001 R12: 0000000000000001 R13: 0000000000000000 R14: 0000000000000001 R15: ffff8818b7097ea0 FS: 00007fb828ece700(0000) GS:ffff88193ec20000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b CR2: 0000000000000000 CR3: 00000018cc7e9000 CR4: 00000000000006e0 Stack: ffffffffa06ff395 ffff8818d465e000 ffffffff8164bec0 0000000000000001 0000000000000050 ffff8818b7097e18 ffffffffa06ff785 ffff8818b7097e38 0000000000000246 0000000054755e3a 0000000039f8ba72 ffff8818c174f000 Call Trace: [] ? test_spinlock+0x65/0x90 [locktest] [] etime_show+0xd5/0x120 [locktest] [] kobj_attr_show+0x16/0x20 [] sysfs_kf_seq_show+0xca/0x1b0 [] kernfs_seq_show+0x23/0x30 [] seq_read+0xbb/0x400 [] kernfs_fop_read+0x35/0x40 [] vfs_read+0xa3/0x110 [] SyS_read+0x56/0xd0 [] ? __audit_syscall_exit+0x216/0x2c0 [] system_call_fastpath+0x16/0x1b Code: Bad RIP value. RSP CR2: 0000000000000000 ---[ end trace 69d0e259c9ec632f ]--- It seems like call site patching isn't properly done or the kernel module that I built was missing some critical information necessary for the proper linking. Anyway, I will include the unlock call patching code as a separate patch as it seems there may be problem under certain circumstance. BTW, the kernel panic problem that your team reported had been fixed. The fix will be in the next version of the patch. -Longman