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* [PATCH v2] KVM: kvmclock: Fix vCPUs > 64 can't be online/hotpluged
@ 2021-01-18  9:07 Wanpeng Li
  2021-01-26  1:28 ` Wanpeng Li
  0 siblings, 1 reply; 5+ messages in thread
From: Wanpeng Li @ 2021-01-18  9:07 UTC (permalink / raw)
  To: linux-kernel, kvm
  Cc: Paolo Bonzini, Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li,
	Jim Mattson, Joerg Roedel, Brijesh Singh

From: Wanpeng Li <wanpengli@tencent.com>

The per-cpu vsyscall pvclock data pointer assigns either an element of the 
static array hv_clock_boot (#vCPU <= 64) or dynamically allocated memory 
hvclock_mem (vCPU > 64), the dynamically memory will not be allocated if 
kvmclock vsyscall is disabled, this can result in cpu hotpluged fails in 
kvmclock_setup_percpu() which returns -ENOMEM. This patch fixes it by not 
assigning vsyscall pvclock data pointer if kvmclock vdso_clock_mode is not 
VDSO_CLOCKMODE_PVCLOCK.

Fixes: 6a1cac56f4 ("x86/kvm: Use __bss_decrypted attribute in shared variables")
Reported-by: Zelin Deng <zelin.deng@linux.alibaba.com>
Tested-by: Haiwei Li <lihaiwei@tencent.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: stable@vger.kernel.org#v4.19-rc5+
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
---
v1 -> v2:
 * add code comments

 arch/x86/kernel/kvmclock.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index aa59374..01d4e55c 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -294,9 +294,11 @@ static int kvmclock_setup_percpu(unsigned int cpu)
 	/*
 	 * The per cpu area setup replicates CPU0 data to all cpu
 	 * pointers. So carefully check. CPU0 has been set up in init
-	 * already.
+	 * already. Assign vsyscall pvclock data pointer iff kvmclock
+	 * vsyscall is enabled.
 	 */
-	if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)))
+	if (!cpu || (p && p != per_cpu(hv_clock_per_cpu, 0)) ||
+	    (kvm_clock.vdso_clock_mode != VDSO_CLOCKMODE_PVCLOCK))
 		return 0;
 
 	/* Use the static page for the first CPUs, allocate otherwise */
-- 
2.7.4


^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2021-01-28  7:42 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-01-18  9:07 [PATCH v2] KVM: kvmclock: Fix vCPUs > 64 can't be online/hotpluged Wanpeng Li
2021-01-26  1:28 ` Wanpeng Li
2021-01-26 17:26   ` Paolo Bonzini
2021-01-27  0:28     ` Wanpeng Li
2021-01-28  7:41       ` Wanpeng Li

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