linux-kernel - Re: [PATCH 3/6] iommu/amd: Introduce amd_iommu_get_num

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Date:	Mon, 28 Dec 2015 16:43:00 +0100
From:	Joerg Roedel <joro@...tes.org>
To:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
Cc:	bp@...en8.de, peterz@...radead.org, mingo@...hat.com,
	acme@...nel.org, linux-kernel@...r.kernel.org,
	iommu@...ts.linux-foundation.org
Subject: Re: [PATCH 3/6] iommu/amd: Introduce amd_iommu_get_num_iommus()

On Tue, Dec 22, 2015 at 01:19:14PM -0600, Suthikulpanit, Suravee wrote:
> This patch introduces amd_iommu_get_num_iommus(). Initially, this is
> intended to be used by Perf AMD IOMMU driver.
> 
> Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
> ---
>  drivers/iommu/amd_iommu_init.c            | 16 ++++++++++++++++
>  include/linux/perf/perf_event_amd_iommu.h |  2 ++
>  2 files changed, 18 insertions(+)
> 
> diff --git a/drivers/iommu/amd_iommu_init.c b/drivers/iommu/amd_iommu_init.c
> index 275c0f5..9c62613 100644
> --- a/drivers/iommu/amd_iommu_init.c
> +++ b/drivers/iommu/amd_iommu_init.c
> @@ -2244,6 +2244,22 @@ bool amd_iommu_v2_supported(void)
>  }
>  EXPORT_SYMBOL(amd_iommu_v2_supported);
>  
> +static int amd_iommu_cnt;
> +
> +int amd_iommu_get_num_iommus(void)
> +{
> +	struct amd_iommu *iommu;
> +
> +	if (amd_iommu_cnt)
> +		return amd_iommu_cnt;
> +
> +	for_each_iommu(iommu)
> +		amd_iommu_cnt++;

It is better to set amd_iommu_cnt during IOMMU initialization. You can
just increment this value after an IOMMU has been set up.



	Joerg

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