Re: [Xen-devel] [PATCH v5 18/21] xen/arm: Add virtual GICv3 support

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 16 Jun 2014, Stefano Stabellini wrote:
> On Sun, 15 Jun 2014, Julien Grall wrote:
> > Hi Stefano,
> > 
> > On 12/06/14 18:09, Stefano Stabellini wrote:
> > > On Thu, 12 Jun 2014, vijay.kilari@xxxxxxxxx wrote:
> > > > +    switch ( gicd_reg )
> > > > +    {
> > > > +    case GICD_CTLR:
> > > > +        if ( dabt.size != DABT_WORD ) goto bad_width;
> > > > +        vgic_lock(v);
> > > > +        *r = v->domain->arch.vgic.ctlr;
> > > > +        vgic_unlock(v);
> > > > +        return 1;
> > > > +    case GICD_TYPER:
> > > > +        if ( dabt.size != DABT_WORD ) goto bad_width;
> > > > +        /* No secure world support for guests. */
> > > > +        *r = (((v->domain->max_vcpus << 5) & GICD_TYPE_CPUS ) |
> > > > +              ((v->domain->arch.vgic.nr_lines / 32) & 
> > > > GICD_TYPE_LINES));
> > > > +        return 1;
> > > 
> > > There used to be a vgic_lock(v) and vgic_unlock(v) here. Why did you
> > > remove them?
> > 
> > I don't think it's important to take the vgic lock here. Xen only access
> > read-only data, max_vcpus and nr_lines doesn't change.
> 
> OK. It should be written in the commit message.

You could write something like:

The GICD emulation for GICv3 is taken from the original GICD emulation
for GICv2. One difference is that we don't take the vgic lock to read
GICD_TYPER.

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