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

["Chen, Yu C" <yu.c.chen@intel.com>]

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