linux-kernel - Re: [RFC PATCH 06/33] irqchip/gic-v3-its: Add probing for VLPI properties

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Date:   Thu, 16 Feb 2017 14:46:03 +0100
From:   Auger Eric <eric.auger@...hat.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <marc.zyngier@....com>
Cc:     Jason Cooper <jason@...edaemon.net>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        Christoffer Dall <christoffer.dall@...aro.org>
Subject: Re: [RFC PATCH 06/33] irqchip/gic-v3-its: Add probing for VLPI
 properties

Hi,

On 13/02/2017 11:00, Thomas Gleixner wrote:
> On Tue, 17 Jan 2017, Marc Zyngier wrote:
>> +	typer = gic_read_typer(its_base + GITS_TYPER);
>>  	its->base = its_base;
>>  	its->phys_base = res->start;
>> -	its->ite_size = ((gic_read_typer(its_base + GITS_TYPER) >> 4) & 0xf) + 1;
>> +	its->ite_size = ((typer >> 4) & 0xf) + 1;
>> +	its->is_v4 = !!(typer & GITS_TYPER_VLPIS);
>> +	if (its->is_v4 && !(typer & GITS_TYPER_VMOVP)) {
>> +		int its_number;
>> +
>> +		its_number = find_first_zero_bit(&its_list_map, 16);
> 
> s/16/ITS_MAX_ENTITIES or whatever.
> 
>> +		if (its_number >= 16) {
>> +			pr_err("ITS@%pa: No ITSList entry available!\n",
>> +			       &res->start);
>> +			err = -EINVAL;
>> +			goto out_free_its;
>> +		}
>> +
>> +		ctlr = readl_relaxed(its_base + GITS_CTLR);
>> +		ctlr &= ~GITS_CTLR_ITS_NUMBER;
>> +		ctlr |= its_number << GITS_CTLR_ITS_NUMBER_SHIFT;
>> +		writel_relaxed(ctlr, its_base + GITS_CTLR);
>> +		ctlr = readl_relaxed(its_base + GITS_CTLR);
>> +		if ((ctlr & GITS_CTLR_ITS_NUMBER) != (its_number << GITS_CTLR_ITS_NUMBER_SHIFT)) {
>> +			its_number = ctlr & GITS_CTLR_ITS_NUMBER;
>> +			its_number >>= GITS_CTLR_ITS_NUMBER_SHIFT;
>> +		}
>> +
>> +		if (test_and_set_bit(its_number, &its_list_map)) {
> 
> You just established above that the bit is not set. I assume that this is
> code which has no concurrency concerns....

I understand this covers the case where the ITS_number field is RO. In
such a case the its_number has changed just above compared to the first
find_first_zero_bit?

Besides

Reviewed-by: Eric Auger <eric.auger@...hat.com>

Thanks

Eric

> 
> Thanks,
> 
> 	tglx
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

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