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xen/vcpu: Handle xen_vcpu_setup() failure in hotplug

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The hypercall VCPUOP_register_vcpu_info can fail. This failure is
handled by making per_cpu(xen_vcpu, cpu) point to its shared_info
slot and those without one (cpu >= MAX_VIRT_CPUS) be NULL.

For PVH/PVHVM, this is not enough, because we also need to pull
these VCPUs out of circulation.

Fix for PVH/PVHVM: on registration failure in the cpuhp prepare
callback (xen_cpu_up_prepare_hvm()), return an error to the cpuhp
state-machine so it can fail the CPU init.

Fix for PV: the registration happens before smp_init(), so, in the
failure case we clamp setup_max_cpus and limit the number of VCPUs
that smp_init() will bring-up to MAX_VIRT_CPUS.
This is functionally correct but it makes the code a bit simpler
if we get rid of this explicit clamping: for VCPUs that don't have
valid xen_vcpu, fail the CPU init in the cpuhp prepare callback
(xen_cpu_up_prepare_pv()).

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Ankur Arora
2017-06-02 17:06:01 -07:00
committed by Juergen Gross
parent 0e4d583723
commit c9b5d98b25
4 changed files with 45 additions and 26 deletions
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9
arch/x86/xen/enlighten_hvm.c
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@@ -89,7 +89,7 @@ static void xen_hvm_crash_shutdown(struct pt_regs *regs)
static int xen_cpu_up_prepare_hvm(unsigned int cpu)
{
int rc;
int rc = 0;
/*
* This can happen if CPU was offlined earlier and
@@ -104,7 +104,9 @@ static int xen_cpu_up_prepare_hvm(unsigned int cpu)
per_cpu(xen_vcpu_id, cpu) = cpu_acpi_id(cpu);
else
per_cpu(xen_vcpu_id, cpu) = cpu;
xen_vcpu_setup(cpu);
rc = xen_vcpu_setup(cpu);
if (rc)
return rc;
if (xen_have_vector_callback && xen_feature(XENFEAT_hvm_safe_pvclock))
xen_setup_timer(cpu);
@@ -113,9 +115,8 @@ static int xen_cpu_up_prepare_hvm(unsigned int cpu)
if (rc) {
WARN(1, "xen_smp_intr_init() for CPU %d failed: %d\n",
cpu, rc);
return rc;
}
return 0;
return rc;
}
static int xen_cpu_dead_hvm(unsigned int cpu)