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: <20200820222129.GA1571389@bjorn-Precision-5520>
Date:   Thu, 20 Aug 2020 17:21:29 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Jonathan Cameron <Jonathan.Cameron@...wei.com>
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 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) {

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) {

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