From: Wei Liu <wei.liu@kernel.org>
To: Linux on Hyper-V List <linux-hyperv@vger.kernel.org>
Cc: Michael Kelley <mikelley@microsoft.com>,
Wei Liu <wei.liu@kernel.org>,
stable@kernel.org, "K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
"H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org (open list:X86 ARCHITECTURE (32-BIT
AND 64-BIT))
Subject: [PATCH] x86/hyperv: check cpu mask after interrupt has been disabled
Date: Tue, 5 Jan 2021 17:50:43 +0000 [thread overview]
Message-ID: <20210105175043.28325-1-wei.liu@kernel.org> (raw)
We've observed crashes due to an empty cpu mask in
hyperv_flush_tlb_others. Obviously the cpu mask in question is changed
between the cpumask_empty call at the beginning of the function and when
it is actually used later.
One theory is that an interrupt comes in between and a code path ends up
changing the mask. Move the check after interrupt has been disabled to
see if it fixes the issue.
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Cc: stable@kernel.org
---
arch/x86/hyperv/mmu.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/arch/x86/hyperv/mmu.c b/arch/x86/hyperv/mmu.c
index 5208ba49c89a..2c87350c1fb0 100644
--- a/arch/x86/hyperv/mmu.c
+++ b/arch/x86/hyperv/mmu.c
@@ -66,11 +66,17 @@ static void hyperv_flush_tlb_others(const struct cpumask *cpus,
if (!hv_hypercall_pg)
goto do_native;
- if (cpumask_empty(cpus))
- return;
-
local_irq_save(flags);
+ /*
+ * Only check the mask _after_ interrupt has been disabled to avoid the
+ * mask changing under our feet.
+ */
+ if (cpumask_empty(cpus)) {
+ local_irq_restore(flags);
+ return;
+ }
+
flush_pcpu = (struct hv_tlb_flush **)
this_cpu_ptr(hyperv_pcpu_input_arg);
--
2.20.1
next reply other threads:[~2021-01-05 17:51 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-05 17:50 Wei Liu [this message]
2021-01-05 18:20 ` [PATCH] x86/hyperv: check cpu mask after interrupt has been disabled Michael Kelley
2021-01-06 11:04 ` Wei Liu
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