Re: [PATCH v3 1/4] x86/kvm: add boot parameter for adding vcpu-id bits

[Juergen Gross]

On 18.11.21 00:44, Sean Christopherson wrote:
> On Tue, Nov 16, 2021, Juergen Gross wrote:
> > diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
> > index 816a82515dcd..64ba9b1c8b3d 100644
> > --- a/arch/x86/kvm/ioapic.c
> > +++ b/arch/x86/kvm/ioapic.c
> > @@ -685,11 +685,21 @@ static const struct kvm_io_device_ops ioapic_mmio_ops = {
> >   int kvm_ioapic_init(struct kvm *kvm)
> >   {
> >   	struct kvm_ioapic *ioapic;
> > +	size_t sz;
> >   	int ret;
> >   
> > -	ioapic = kzalloc(sizeof(struct kvm_ioapic), GFP_KERNEL_ACCOUNT);
> > +	sz = sizeof(struct kvm_ioapic) +
> > +	     sizeof(*ioapic->rtc_status.dest_map.map) *
> > +		    BITS_TO_LONGS(KVM_MAX_VCPU_IDS) +
> > +	     sizeof(*ioapic->rtc_status.dest_map.vectors) *
> > +		    (KVM_MAX_VCPU_IDS);
> > +	ioapic = kzalloc(sz, GFP_KERNEL_ACCOUNT);
> >   	if (!ioapic)
> >   		return -ENOMEM;
> > +	ioapic->rtc_status.dest_map.map = (void *)(ioapic + 1);
>
> Oof.  Just do separate allocations.  I highly doubt the performance of the
> emulated RTC hinges on the spatial locality of the bitmap and array.  The array
> is going to end up in a second page for most configuration anyways.

Okay, fine with me.


Juergen

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