5.7-stable patches

added patches:
	xen-don-t-reschedule-in-preemption-off-sections.patch

diff --git a/queue-5.7/series b/queue-5.7/series
index 5d8f008a290d17dfbd9b0ef8586fdcfa8399d41a..c24bcac7afdcb199233d25c85e6deb186f836d1d 100644 (file)
--- a/queue-5.7/series
+++ b/queue-5.7/series
@@ -121,3 +121,4 @@ efi-add-missed-destroy_workqueue-when-efisubsys_init-fails.patch
 efi-libstub-stop-parsing-arguments-at.patch
 efi-libstub-handle-null-cmdline.patch
 do_epoll_ctl-clean-the-failure-exits-up-a-bit.patch
+xen-don-t-reschedule-in-preemption-off-sections.patch

diff --git a/queue-5.7/xen-don-t-reschedule-in-preemption-off-sections.patch b/queue-5.7/xen-don-t-reschedule-in-preemption-off-sections.patch
new file mode 100644 (file)
index 0000000..7cf6b85
--- /dev/null
+++ b/queue-5.7/xen-don-t-reschedule-in-preemption-off-sections.patch
@@ -0,0 +1,96 @@
+From jgross@suse.com  Mon Aug 24 10:12:00 2020
+From: Juergen Gross <jgross@suse.com>
+Date: Thu, 20 Aug 2020 08:59:08 +0200
+Subject: xen: don't reschedule in preemption off sections
+To: stable@vger.kernel.org
+Cc: xen-devel@lists.xenproject.org, Juergen Gross <jgross@suse.com>, Boris Ostrovsky <boris.ostrovsky@oracle.com>, Stefano Stabellini <sstabellini@kernel.org>, Sarah Newman <srn@prgmr.com>, Chris Brannon <cmb@prgmr.com>
+Message-ID: <20200820065908.20592-1-jgross@suse.com>
+
+From: Juergen Gross <jgross@suse.com>
+
+For support of long running hypercalls xen_maybe_preempt_hcall() is
+calling cond_resched() in case a hypercall marked as preemptible has
+been interrupted.
+
+Normally this is no problem, as only hypercalls done via some ioctl()s
+are marked to be preemptible. In rare cases when during such a
+preemptible hypercall an interrupt occurs and any softirq action is
+started from irq_exit(), a further hypercall issued by the softirq
+handler will be regarded to be preemptible, too. This might lead to
+rescheduling in spite of the softirq handler potentially having set
+preempt_disable(), leading to splats like:
+
+BUG: sleeping function called from invalid context at drivers/xen/preempt.c:37
+in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 20775, name: xl
+INFO: lockdep is turned off.
+CPU: 1 PID: 20775 Comm: xl Tainted: G D W 5.4.46-1_prgmr_debug.el7.x86_64 #1
+Call Trace:
+<IRQ>
+dump_stack+0x8f/0xd0
+___might_sleep.cold.76+0xb2/0x103
+xen_maybe_preempt_hcall+0x48/0x70
+xen_do_hypervisor_callback+0x37/0x40
+RIP: e030:xen_hypercall_xen_version+0xa/0x20
+Code: ...
+RSP: e02b:ffffc900400dcc30 EFLAGS: 00000246
+RAX: 000000000004000d RBX: 0000000000000200 RCX: ffffffff8100122a
+RDX: ffff88812e788000 RSI: 0000000000000000 RDI: 0000000000000000
+RBP: ffffffff83ee3ad0 R08: 0000000000000001 R09: 0000000000000001
+R10: 0000000000000000 R11: 0000000000000246 R12: ffff8881824aa0b0
+R13: 0000000865496000 R14: 0000000865496000 R15: ffff88815d040000
+? xen_hypercall_xen_version+0xa/0x20
+? xen_force_evtchn_callback+0x9/0x10
+? check_events+0x12/0x20
+? xen_restore_fl_direct+0x1f/0x20
+? _raw_spin_unlock_irqrestore+0x53/0x60
+? debug_dma_sync_single_for_cpu+0x91/0xc0
+? _raw_spin_unlock_irqrestore+0x53/0x60
+? xen_swiotlb_sync_single_for_cpu+0x3d/0x140
+? mlx4_en_process_rx_cq+0x6b6/0x1110 [mlx4_en]
+? mlx4_en_poll_rx_cq+0x64/0x100 [mlx4_en]
+? net_rx_action+0x151/0x4a0
+? __do_softirq+0xed/0x55b
+? irq_exit+0xea/0x100
+? xen_evtchn_do_upcall+0x2c/0x40
+? xen_do_hypervisor_callback+0x29/0x40
+</IRQ>
+? xen_hypercall_domctl+0xa/0x20
+? xen_hypercall_domctl+0x8/0x20
+? privcmd_ioctl+0x221/0x990 [xen_privcmd]
+? do_vfs_ioctl+0xa5/0x6f0
+? ksys_ioctl+0x60/0x90
+? trace_hardirqs_off_thunk+0x1a/0x20
+? __x64_sys_ioctl+0x16/0x20
+? do_syscall_64+0x62/0x250
+? entry_SYSCALL_64_after_hwframe+0x49/0xbe
+
+Fix that by testing preempt_count() before calling cond_resched().
+
+In kernel 5.8 this can't happen any more due to the entry code rework
+(more than 100 patches, so not a candidate for backporting).
+
+The issue was introduced in kernel 4.3, so this patch should go into
+all stable kernels in [4.3 ... 5.7].
+
+Reported-by: Sarah Newman <srn@prgmr.com>
+Fixes: 0fa2f5cb2b0ecd8 ("sched/preempt, xen: Use need_resched() instead of should_resched()")
+Cc: Sarah Newman <srn@prgmr.com>
+Cc: stable@vger.kernel.org
+Signed-off-by: Juergen Gross <jgross@suse.com>
+Tested-by: Chris Brannon <cmb@prgmr.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/xen/preempt.c |    2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+--- a/drivers/xen/preempt.c
++++ b/drivers/xen/preempt.c
+@@ -27,7 +27,7 @@ EXPORT_SYMBOL_GPL(xen_in_preemptible_hca
+ asmlinkage __visible void xen_maybe_preempt_hcall(void)
+ {
+       if (unlikely(__this_cpu_read(xen_in_preemptible_hcall)
+-                   && need_resched())) {
++                   && need_resched() && !preempt_count())) {
+               /*
+                * Clear flag as we may be rescheduled on a different
+                * cpu.