Re: [PATCH 08/31] nVMX: Fix local_vcpus_link handling

[Avi Kivity <avi@redhat.com>]

On 05/17/2011 04:19 PM, Marcelo Tosatti wrote:
> >  +/*
> >  + * Maintain the vcpus_on_cpu and saved_vmcss_on_cpu lists of vcpus and
> >  + * inactive saved_vmcss on nested entry (L1->L2) or nested exit (L2->L1).
> >  + *
> >  + * nested_maintain_per_cpu_lists should be called after the VMCS was switched
> >  + * to the new one, with parameters giving both the new on (after the entry
> >  + * or exit) and the old one, in that order.
> >  + */
> >  +static void nested_maintain_per_cpu_lists(struct vcpu_vmx *vmx,
> >  +		struct saved_vmcs *new_vmcs,
> >  +		struct saved_vmcs *old_vmcs)
> >  +{
> >  +	/*
> >  +	 * When a vcpus's old vmcs is saved, we need to drop it from
> >  +	 * vcpus_on_cpu and put it on saved_vmcss_on_cpu.
> >  +	 */
> >  +	if (old_vmcs->cpu != -1) {
> >  +		list_del(&vmx->local_vcpus_link);
> >  +		list_add(&old_vmcs->local_saved_vmcss_link,
> >  +			&per_cpu(saved_vmcss_on_cpu, old_vmcs->cpu));
> >  +	}
>
> This new handling of vmcs could be simplified (local_vcpus_link must be
> manipulated with interrupts disabled, BTW).
>
> What about having a per-CPU VMCS list instead of per-CPU vcpu list?
> "local_vmcs_link" list node could be in "struct saved_vmcs" (and
> a current_saved_vmcs pointer in "struct vcpu_vmx").
>
> vmx_vcpu_load would then add to this list at
>
>          if (per_cpu(current_vmcs, cpu) != vmx->vmcs) {
>                  per_cpu(current_vmcs, cpu) = vmx->vmcs;
>                  vmcs_load(vmx->vmcs);
>          }

Right, that's the easiest thing to do.

Perhaps even easier (avoids duplication):

struct raw_vmcs {
     u32 revision_id;
     u32 abort;
     char data[0];
};

struct vmcs {
     struct raw_vmcs *raw_vmcs;
     struct list_head local_vmcs_link;
};

struct vcpu_vmx {
     ...
     struct vmcs *vmcs;  /* often points at l1_vmcs */
     struct vmcs l1_vmcs;
     ...
};

static DEFINE_PER_CPU(struct list_head, vmcss_on_cpu);

-- 
error compiling committee.c: too many arguments to function