Hi Julien,
Follow your advice, I change the tag to [PATCH v4 for-4.9] because of we
hope this patch can be merged in Xen 4.9.
Hi Jan,
If there have anything need to change in this patch?
Thanks,
Luwei Kang
> -----Original Message-----
> From: Kang, Luwei
> Sent: Tuesday, May 23, 2017 4:46 AM
> To: xen-devel@lists.xen.org
> Cc: jbeul...@suse.com; andrew.coop...@citrix.com; boris.ostrov...@oracle.com;
> Kang, Luwei <luwei.k...@intel.com>
> Subject: [PATCH v4] x86/vpmu: add cpu hot unplug notifier for vpmu
>
> Currently, Hot unplug a physical CPU with vpmu enabled may cause system hang
> due to send a remote call to an offlined pCPU. This
> patch add a cpu hot unplug notifer to save vpmu context before cpu offline.
>
> Consider one scenario, hot unplug pCPU N with vpmu enabled.
> The vcpu which running on this pCPU will be switch to other online cpu. A
> remote call will be send to pCPU N to save the vpmu
> context before loading the vpmu context on this pCPU.
> System will hang in function on_select_cpus() because of that pCPU is
> offlined and can not do any respond.
>
> The purpose of add a VPMU_CONTEXT_LOADED check in vpmu_arch_destroy() before
> send a remote call to save vpmu contex is:
> a. when a vpmu context has been loaded in a remote pCPU, make a
> remote call to save the vpmu contex and stop counters is necessary.
> b. VPMU_CONTEXT_LOADED flag will be reset if a pCPU is offlined.
> this check will prevent send a remote call to an offlined pCPU.
>
> Signed-off-by: Luwei Kang <luwei.k...@intel.com>
> ---
> v4:
> 1.remove cpu_online() check in vpm_load(); 2.remove "vpmu_" prefix; 3.fix
> a coding style; 4.add some commit message about
> VPMU_CONTEXT_LOADED in vpmu_arch_destroy();
> v3:
> 1.add cpu_online() check in vpm_load() and vpmu_arch_destroy(); 2.add vpmu_
> prefix. rename cpu_callback() to
> vpmu_cpu_callback();
> v2:
> 1.fix some typo and coding style;
> 2.change "swith" to "if" in cpu_callback() because of there just have one
> case; 3.add VPMU_CONTEX_LOADED check before send
> remote call in vpmu_arch_destroy();
> ---
> xen/arch/x86/cpu/vpmu.c | 45 +++++++++++++++++++++++++++++++++++++++++----
> 1 file changed, 41 insertions(+), 4 deletions(-)
>
> diff --git a/xen/arch/x86/cpu/vpmu.c b/xen/arch/x86/cpu/vpmu.c index
> 03401fd..1f7830b 100644
> --- a/xen/arch/x86/cpu/vpmu.c
> +++ b/xen/arch/x86/cpu/vpmu.c
> @@ -21,6 +21,7 @@
> #include <xen/xenoprof.h>
> #include <xen/event.h>
> #include <xen/guest_access.h>
> +#include <xen/cpu.h>
> #include <asm/regs.h>
> #include <asm/types.h>
> #include <asm/msr.h>
> @@ -575,15 +576,21 @@ static void vpmu_arch_destroy(struct vcpu *v)
> * We will test it again in vpmu_clear_last() with interrupts
> * disabled to make sure we don't clear someone else.
> */
> - if ( per_cpu(last_vcpu, vpmu->last_pcpu) == v )
> + if ( cpu_online(vpmu->last_pcpu) &&
> + per_cpu(last_vcpu, vpmu->last_pcpu) == v )
> on_selected_cpus(cpumask_of(vpmu->last_pcpu),
> vpmu_clear_last, v, 1);
>
> if ( vpmu->arch_vpmu_ops && vpmu->arch_vpmu_ops->arch_vpmu_destroy )
> {
> - /* Unload VPMU first. This will stop counters */
> - on_selected_cpus(cpumask_of(vcpu_vpmu(v)->last_pcpu),
> - vpmu_save_force, v, 1);
> + /*
> + * Unload VPMU first if VPMU_CONTEXT_LOADED being set.
> + * This will stop counters.
> + */
> + if ( vpmu_is_set(vpmu, VPMU_CONTEXT_LOADED) )
> + on_selected_cpus(cpumask_of(vcpu_vpmu(v)->last_pcpu),
> + vpmu_save_force, v, 1);
> +
> vpmu->arch_vpmu_ops->arch_vpmu_destroy(v);
> }
> }
> @@ -835,6 +842,33 @@ long do_xenpmu_op(unsigned int op,
> XEN_GUEST_HANDLE_PARAM(xen_pmu_params_t) arg)
> return ret;
> }
>
> +static int cpu_callback(
> + struct notifier_block *nfb, unsigned long action, void *hcpu) {
> + unsigned int cpu = (unsigned long)hcpu;
> + struct vcpu *vcpu = per_cpu(last_vcpu, cpu);
> + struct vpmu_struct *vpmu;
> +
> + if ( !vcpu )
> + return NOTIFY_DONE;
> +
> + vpmu = vcpu_vpmu(vcpu);
> + if ( !vpmu_is_set(vpmu, VPMU_CONTEXT_ALLOCATED) )
> + return NOTIFY_DONE;
> +
> + if ( action == CPU_DYING )
> + {
> + vpmu_save_force(vcpu);
> + vpmu_reset(vpmu, VPMU_CONTEXT_LOADED);
> + }
> +
> + return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block cpu_nfb = {
> + .notifier_call = cpu_callback
> +};
> +
> static int __init vpmu_init(void)
> {
> int vendor = current_cpu_data.x86_vendor; @@ -872,8 +906,11 @@ static
> int __init vpmu_init(void)
> }
>
> if ( vpmu_mode != XENPMU_MODE_OFF )
> + {
> + register_cpu_notifier(&cpu_nfb);
> printk(XENLOG_INFO "VPMU: version " __stringify(XENPMU_VER_MAJ) "."
> __stringify(XENPMU_VER_MIN) "\n");
> + }
> else
> opt_vpmu_enabled = 0;
>
> --
> 1.8.3.1
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