Re: [Xen-devel] [PATCH] When flush tlb , we need consider the cpu_online_map

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> 29.03.10 14:00 >>>
>When flush tlb mask, we need consider the cpu_online_map. The same happens to 
>ept flush also.

While the idea is certainly correct, doing this more efficiently seems
quite desirable to me, especially when NR_CPUS is large:

>--- a/xen/arch/x86/hvm/vmx/vmx.c       Sat Mar 27 16:01:35 2010 +0000
>+++ b/xen/arch/x86/hvm/vmx/vmx.c       Mon Mar 29 17:49:51 2010 +0800
>@@ -1235,6 +1235,9 @@ void ept_sync_domain(struct domain *d)
>      * unnecessary extra flushes, to avoid allocating a cpumask_t on the 
> stack.
>      */
>     d->arch.hvm_domain.vmx.ept_synced = d->domain_dirty_cpumask;
>+    cpus_and(d->arch.hvm_domain.vmx.ept_synced,
>+             d->arch.hvm_domain.vmx.ept_synced,
>+             cpu_online_map);

The added code can be combined with the pre-existing line:

    cpus_and(d->arch.hvm_domain.vmx.ept_synced,
             d->domain_dirty_cpumask, cpu_online_map);

>     on_selected_cpus(&d->arch.hvm_domain.vmx.ept_synced,
>                      __ept_sync_domain, d, 1);
> }
>--- a/xen/arch/x86/smp.c       Sat Mar 27 16:01:35 2010 +0000
>+++ b/xen/arch/x86/smp.c       Mon Mar 29 17:47:25 2010 +0800
>@@ -229,6 +229,7 @@ void flush_area_mask(const cpumask_t *ma
>     {
>         spin_lock(&flush_lock);
>         cpus_andnot(flush_cpumask, *mask, *cpumask_of(smp_processor_id()));
>+        cpus_and(flush_cpumask, cpu_online_map, flush_cpumask);

Here, first doing the full-mask operation and then clearing the one
extra bit is less overhead:

        cpus_and(flush_cpumask, *mask, cpu_online_map);
        cpu_clear(smp_processor_id(), flush_cpumask);

>         flush_va      = va;
>         flush_flags   = flags;
>         send_IPI_mask(&flush_cpumask, INVALIDATE_TLB_VECTOR);

Jan




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