linux-kernel - [PATCH 3/4] xen/smp/pvhvm: Don't point per_cpu(xen_vpcu, 33 and larger) to shared

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Message-Id: <1367845498-14290-4-git-send-email-konrad.wilk@oracle.com>
Date:	Mon,  6 May 2013 09:04:57 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
	stefano.stabellini@...citrix.com
Cc:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: [PATCH 3/4] xen/smp/pvhvm: Don't point per_cpu(xen_vpcu, 33 and larger) to shared_info

As it will point to some data, but not event channel data (the
shared_info has an array limited to 32).

This means that for PVHVM guests with more than 32 VCPUs without
the usage of VCPUOP_register_info any interrupts to VCPUs
larger than 32 would have gone unnoticed during early bootup.

That is OK, as during early bootup, in smp_init we end up calling
the hotplug mechanism (xen_hvm_cpu_notify) which makes the
VCPUOP_register_vcpu_info call for all VCPUs and we can receive
interrupts on VCPUs 33 and further.

This is just a cleanup.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
---
 arch/x86/xen/enlighten.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 9b34475..18a4009 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1638,6 +1638,9 @@ void __ref xen_hvm_init_shared_info(void)
 	 * online but xen_hvm_init_shared_info is run at resume time too and
 	 * in that case multiple vcpus might be online. */
 	for_each_online_cpu(cpu) {
+		/* Leave it to be NULL. */
+		if (cpu >= MAX_VIRT_CPUS)
+			continue;
 		per_cpu(xen_vcpu, cpu) = &HYPERVISOR_shared_info->vcpu_info[cpu];
 	}
 }
-- 
1.8.1.4

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