Re: [PATCH] drm/amdkfd: add ACPI SRAT parsing for topology

[Felix Kuehling <felix.kuehling@amd.com>]

Am 2021-05-03 um 10:47 a.m. schrieb Eric Huang:
> In NPS4 BIOS we need to find the closest numa node when creating
> topology io link between cpu and gpu, if PCI driver doesn't set
> it.
>
> Signed-off-by: Eric Huang <jinhuieric.huang@amd.com>
> ---
>  drivers/gpu/drm/amd/amdkfd/kfd_crat.c | 95 ++++++++++++++++++++++++++-
>  1 file changed, 93 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_crat.c b/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
> index 38d45711675f..58c6738de774 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_crat.c
> @@ -1759,6 +1759,91 @@ static int kfd_fill_gpu_memory_affinity(int *avail_size,
>  	return 0;
>  }
>  
> +#ifdef CONFIG_ACPI_NUMA
> +static void kfd_find_numa_node_in_srat(struct kfd_dev *kdev)
> +{
> +	struct acpi_table_header *table_header = NULL;
> +	struct acpi_subtable_header *sub_header = NULL;
> +	unsigned long table_end, subtable_len;
> +	u32 pci_id = pci_domain_nr(kdev->pdev->bus) << 16 |
> +			pci_dev_id(kdev->pdev);
> +	u32 bdf;
> +	acpi_status status;
> +	struct acpi_srat_cpu_affinity *cpu;
> +	struct acpi_srat_generic_affinity *gpu;
> +	int pxm = 0, max_pxm = 0;
> +	int numa_node = NUMA_NO_NODE;
> +	bool found = false;
> +
> +	/* Fetch the SRAT table from ACPI */
> +	status = acpi_get_table(ACPI_SIG_SRAT, 0, &table_header);
> +	if (status == AE_NOT_FOUND) {
> +		pr_warn("SRAT table not found\n");
> +		return;
> +	} else if (ACPI_FAILURE(status)) {
> +		const char *err = acpi_format_exception(status);
> +		pr_err("SRAT table error: %s\n", err);
> +		return;
> +	}
> +
> +	table_end = (unsigned long)table_header + table_header->length;
> +
> +	/* Parse all entries looking for a match. */
> +	sub_header = (struct acpi_subtable_header *)
> +			((unsigned long)table_header +
> +			sizeof(struct acpi_table_srat));
> +	subtable_len = sub_header->length;
> +
> +	while (((unsigned long)sub_header) + subtable_len  < table_end) {
> +		/*
> +		 * If length is 0, break from this loop to avoid
> +		 * infinite loop.
> +		 */
> +		if (subtable_len == 0) {
> +			pr_err("SRAT invalid zero length\n");
> +			break;
> +		}
> +
> +		switch (sub_header->type) {
> +		case ACPI_SRAT_TYPE_CPU_AFFINITY:
> +			cpu = (struct acpi_srat_cpu_affinity *)sub_header;
> +			pxm = *((u32 *)cpu->proximity_domain_hi) << 8 |
> +					cpu->proximity_domain_lo;
> +			if (pxm > max_pxm)
> +				max_pxm = pxm;
> +			break;
> +		case ACPI_SRAT_TYPE_GENERIC_AFFINITY:
> +			gpu = (struct acpi_srat_generic_affinity *)sub_header;
> +			bdf = *((u16 *)(&gpu->device_handle[0])) << 16 |
> +					*((u16 *)(&gpu->device_handle[2]));
> +			if (bdf == pci_id) {
> +				found = true;
> +				numa_node = pxm_to_node(gpu->proximity_domain);
> +			}
> +			break;
> +		default:
> +			break;
> +		}
> +
> +		if (found)
> +			break;
> +
> +		sub_header = (struct acpi_subtable_header *)
> +				((unsigned long)sub_header + subtable_len);
> +		subtable_len = sub_header->length;
> +	}
> +
> +	acpi_put_table(table_header);
> +
> +	/* Workaround bad cpu-gpu binding case */
> +	if (found && (numa_node < 0 || numa_node > max_pxm))
> +		numa_node = 0;
> +
> +	if (numa_node != NUMA_NO_NODE)
> +		set_dev_node(&kdev->pdev->dev, numa_node);
> +}
> +#endif
> +
>  /* kfd_fill_gpu_direct_io_link - Fill in direct io link from GPU
>   * to its NUMA node
>   *	@avail_size: Available size in the memory
> @@ -1804,10 +1889,16 @@ static int kfd_fill_gpu_direct_io_link_to_cpu(int *avail_size,
>  	}
>  
>  	sub_type_hdr->proximity_domain_from = proximity_domain;
> -#ifdef CONFIG_NUMA
> +
> +#ifdef CONFIG_ACPI_NUMA
>  	if (kdev->pdev->dev.numa_node == NUMA_NO_NODE)
> +		kfd_find_numa_node_in_srat(kdev);
> +#endif
> +#ifdef CONFIG_NUMA
> +	if (kdev->pdev->dev.numa_node == NUMA_NO_NODE) {
>  		sub_type_hdr->proximity_domain_to = 0;
> -	else
> +		set_dev_node(&kdev->pdev->dev, 0);

This should not be here. If you really want to lie about the NUMA node
and pretend that it's 0 and not NO_NODE, then that should be done in
kfd_find_numa_node_in_srat. That should be the only function that
changes the dev->numa_node. Like Oak pointed out, eventually that should
maybe not even be part of the driver. But I'm OK with keeping it as a
fallback in the driver for the case that one a GPU doesn't have a NUMA
node assigned by the kernel.

But is setting the dev->numa_node to 0 really necessary? Does anything
else in KFD depend on the dev->numa_node being 0? This function is only
supposed to fill the proximity_domain in the CRAT table. Setting
dev->numa_node is a side effect. If we can't figure out the correct NUMA
node, we shouldn't just guess 0 in a way that potentially affects other
parts of the kernel.

Regards,
  Felix


> +	} else
>  		sub_type_hdr->proximity_domain_to = kdev->pdev->dev.numa_node;
>  #else
>  	sub_type_hdr->proximity_domain_to = 0;
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