linux-kernel - Re: [PATCH v9 4/6] ACPI: HMAT: Fix handling of changes from ACPI 6.2 to ACPI 6.3

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Message-ID: <20200821094258.00007925@Huawei.com>
Date:   Fri, 21 Aug 2020 09:42:58 +0100
From:   Jonathan Cameron <Jonathan.Cameron@...wei.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     <linux-mm@...ck.org>, <linux-acpi@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <x86@...nel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, <rafael@...nel.org>,
        <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, <linuxarm@...wei.com>,
        Dan Williams <dan.j.williams@...el.com>,
        "Brice Goglin" <Brice.Goglin@...ia.fr>,
        Sean V Kelley <sean.v.kelley@...ux.intel.com>,
        <linux-api@...r.kernel.org>
Subject: Re: [PATCH v9 4/6] ACPI: HMAT: Fix handling of changes from ACPI
 6.2 to ACPI 6.3

On Thu, 20 Aug 2020 17:21:29 -0500
Bjorn Helgaas <helgaas@...nel.org> wrote:

> On Wed, Aug 19, 2020 at 10:51:09PM +0800, Jonathan Cameron wrote:
> > In ACPI 6.3, the Memory Proximity Domain Attributes Structure
> > changed substantially.  One of those changes was that the flag
> > for "Memory Proximity Domain field is valid" was deprecated.
> > 
> > This was because the field "Proximity Domain for the Memory"
> > became a required field and hence having a validity flag makes
> > no sense.
> > 
> > So the correct logic is to always assume the field is there.
> > Current code assumes it never is.
> > 
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> > ---
> >  drivers/acpi/numa/hmat.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/acpi/numa/hmat.c b/drivers/acpi/numa/hmat.c
> > index 2c32cfb72370..07cfe50136e0 100644
> > --- a/drivers/acpi/numa/hmat.c
> > +++ b/drivers/acpi/numa/hmat.c
> > @@ -424,7 +424,7 @@ static int __init hmat_parse_proximity_domain(union acpi_subtable_headers *heade
> >  		pr_info("HMAT: Memory Flags:%04x Processor Domain:%u Memory Domain:%u\n",
> >  			p->flags, p->processor_PD, p->memory_PD);
> >  
> > -	if (p->flags & ACPI_HMAT_MEMORY_PD_VALID && hmat_revision == 1) {
> > +	if ((p->flags & ACPI_HMAT_MEMORY_PD_VALID && hmat_revision == 1) || hmat_revision == 2) {  
> 

Hi Bjorn,

> I hope/assume the spec is written in such a way that p->memory_PD is
> required for any revision > 1?  So maybe this should be:
> 
>   if ((p->flags & ACPI_HMAT_MEMORY_PD_VALID && hmat_revision == 1) ||
>       hmat_revision > 1) {

Good point.  We have existing protections elsewhere against hmat_revision
being anything other than 1 or 2, so we should aim to keep that in only one place.

I'll tidy this up for v10.

thanks,

Jonathan


> 
> >  		target = find_mem_target(p->memory_PD);
> >  		if (!target) {
> >  			pr_debug("HMAT: Memory Domain missing from SRAT\n");
> > -- 
> > 2.19.1
> >