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Message-ID: <803275d5-58f4-21d9-8020-e56f05737450@de.ibm.com>
Date:   Tue, 22 Feb 2022 09:13:29 +0100
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Subject: Re: [PATCH v3 1/1] KVM: s390: pv: make use of ultravisor AIV support
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To:     Michael Mueller <mimu@linux.ibm.com>, kvm@vger.kernel.org
Cc:     cohuck@redhat.com, frankja@linux.ibm.com, thuth@redhat.com,
        pasic@linux.ibm.com, david@redhat.com, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20220209152217.1793281-1-mimu@linux.ibm.com>
 <20220209152217.1793281-2-mimu@linux.ibm.com>
From:   Christian Borntraeger <borntraeger@de.ibm.com>
In-Reply-To: <20220209152217.1793281-2-mimu@linux.ibm.com>
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Am 09.02.22 um 16:22 schrieb Michael Mueller:
> This patch enables the ultravisor adapter interruption vitualization
> support indicated by UV feature BIT_UV_FEAT_AIV. This allows ISC
> interruption injection directly into the GISA IPM for PV kvm guests.
> 
> Hardware that does not support this feature will continue to use the
> UV interruption interception method to deliver ISC interruptions to
> PV kvm guests. For this purpose, the ECA_AIV bit for all guest cpus
> will be cleared and the GISA will be disabled during PV CPU setup.
> 
> In addition a check in __inject_io() has been removed. That reduces the
> required instructions for interruption handling for PV and traditional
> kvm guests.
> 
> Signed-off-by: Michael Mueller <mimu@linux.ibm.com>

The CI said the following with gisa_disable in the calltrace.
Will drop from next for now.

    LOCKDEP_CIRCULAR (suite: kvm-unit-tests-kvm, case: -)
                 WARNING: possible circular locking dependency detected
                 5.17.0-20220221.rc5.git1.b8f0356a093a.300.fc35.s390x+debug #1 Not tainted
                 ------------------------------------------------------
                 qemu-system-s39/161139 is trying to acquire lock:
                 0000000280dc0b98 (&kvm->lock){+.+.}-{3:3}, at: kvm_s390_set_tod_clock+0x36/0x220 [kvm]
                 but task is already holding lock:
                 0000000280f4e4b8 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x9a/0xa40 [kvm]
                 which lock already depends on the new lock.
                 the existing dependency chain (in reverse order) is:
                 -> #1 (&vcpu->mutex){+.+.}-{3:3}:
                        __lock_acquire+0x604/0xbd8
                        lock_acquire.part.0+0xe2/0x250
                        lock_acquire+0xb0/0x200
                        __mutex_lock+0x9e/0x8a0
                        mutex_lock_nested+0x32/0x40
                        kvm_s390_gisa_disable+0xa4/0x130 [kvm]
                        kvm_s390_handle_pv+0x718/0x778 [kvm]
                        kvm_arch_vm_ioctl+0x4ac/0x5f8 [kvm]
                        kvm_vm_ioctl+0x336/0x530 [kvm]
                        __s390x_sys_ioctl+0xbe/0x100
                        __do_syscall+0x1da/0x208
                        system_call+0x82/0xb0
                 -> #0 (&kvm->lock){+.+.}-{3:3}:
                        check_prev_add+0xe0/0xed8
                        validate_chain+0x736/0xb20
                        __lock_acquire+0x604/0xbd8
                        lock_acquire.part.0+0xe2/0x250
                        lock_acquire+0xb0/0x200
                        __mutex_lock+0x9e/0x8a0
                        mutex_lock_nested+0x32/0x40
                        kvm_s390_set_tod_clock+0x36/0x220 [kvm]
                        kvm_s390_handle_b2+0x378/0x728 [kvm]
                        kvm_handle_sie_intercept+0x13a/0x448 [kvm]
                        vcpu_post_run+0x28e/0x560 [kvm]
                        __vcpu_run+0x266/0x388 [kvm]
                        kvm_arch_vcpu_ioctl_run+0x10a/0x270 [kvm]
                        kvm_vcpu_ioctl+0x27c/0xa40 [kvm]
                        __s390x_sys_ioctl+0xbe/0x100
                        __do_syscall+0x1da/0x208
                        system_call+0x82/0xb0
                 other info that might help us debug this:
                  Possible unsafe locking scenario:
                        CPU0                    CPU1
                        ----                    ----
                   lock(&vcpu->mutex);
                                                lock(&kvm->lock);
                                                lock(&vcpu->mutex);
                   lock(&kvm->lock);
                  *** DEADLOCK ***
                 2 locks held by qemu-system-s39/161139:
                  #0: 0000000280f4e4b8 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x9a/0xa40 [kvm]
                  #1: 0000000280dc47c8 (&kvm->srcu){....}-{0:0}, at: __vcpu_run+0x1d4/0x388 [kvm]
                 stack backtrace:
                 CPU: 10 PID: 161139 Comm: qemu-system-s39 Not tainted 5.17.0-20220221.rc5.git1.b8f0356a093a.300.fc35.s390x+debug #1
                 Hardware name: IBM 8561 T01 701 (LPAR)
                 Call Trace:
                  [<00000001da4e89de>] dump_stack_lvl+0x8e/0xc8
                  [<00000001d9876c56>] check_noncircular+0x136/0x158
                  [<00000001d9877c70>] check_prev_add+0xe0/0xed8
                  [<00000001d987919e>] validate_chain+0x736/0xb20
                  [<00000001d987b23c>] __lock_acquire+0x604/0xbd8
                  [<00000001d987c432>] lock_acquire.part.0+0xe2/0x250
                  [<00000001d987c650>] lock_acquire+0xb0/0x200
                  [<00000001da4f72ae>] __mutex_lock+0x9e/0x8a0
                  [<00000001da4f7ae2>] mutex_lock_nested+0x32/0x40
                  [<000003ff8070cd6e>] kvm_s390_set_tod_clock+0x36/0x220 [kvm]
                  [<000003ff8071dd68>] kvm_s390_handle_b2+0x378/0x728 [kvm]
                  [<000003ff8071146a>] kvm_handle_sie_intercept+0x13a/0x448 [kvm]
                  [<000003ff8070dd46>] vcpu_post_run+0x28e/0x560 [kvm]
                  [<000003ff8070e27e>] __vcpu_run+0x266/0x388 [kvm]
                  [<000003ff8070eba2>] kvm_arch_vcpu_ioctl_run+0x10a/0x270 [kvm]
                  [<000003ff806f4044>] kvm_vcpu_ioctl+0x27c/0xa40 [kvm]
                  [<00000001d9b47ac6>] __s390x_sys_ioctl+0xbe/0x100
                  [<00000001da4ec152>] __do_syscall+0x1da/0x208
                  [<00000001da4fec42>] system_call+0x82/0xb0
                 INFO: lockdep is turned off.