Re: [RFC PATCH 25/31] x86/resctrl: Introduce region-based MBA write implementation on MMIO space

[Chen, Yu C]

On 8/5/2026 5:13 AM, Luck, Tony wrote:
> > +	for (i = m->low; i < m->high; i++) {
> > +		closid_idx = (region / 4) * 64 + i;
> > +		addr = d->base[mmio_type] + closid_idx * 8;
> > +
> > +		/* The cached value retains the reserved bits to be preserved. */
> > +		val = d->marc_buf[closid_idx];
> > +		if (!val)
> > +			val = readq(addr);
> > +
> > +		if (WARN_ON_ONCE(!val))
> > +			return;
> > +
> > +		val &= ~(0x1ffULL << region_offset_bits);
> > +		val |= (u64)(hw_dom->ctrl_val[i] & 0x1ff) << region_offset_bits;
> > +		d->marc_buf[closid_idx] = val;
> > +		writeq(val, addr);
> > +	}
> >   }
>
> There are lots of opinions about bit fields. I'm a fan for h/w registers
> accessed in architecture specific code.
>   
> I think the version below is easier to read than all the inline masks and
> shifts.

Got it, learned a lot, I will revise it in this direction.

thanks,
Chenyu