linux-kernel - Re: [RFC PATCH v5 1/5] iommu: Add capabilities to a group

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Message-ID: <20170809055556.GK13670@umbus.fritz.box>
Date:   Wed, 9 Aug 2017 15:55:56 +1000
From:   David Gibson <david@...son.dropbear.id.au>
To:     Alexey Kardashevskiy <aik@...abs.ru>
Cc:     linuxppc-dev@...ts.ozlabs.org, kvm-ppc@...r.kernel.org,
        kvm@...r.kernel.org, Yongji Xie <elohimes@...il.com>,
        Eric Auger <eric.auger@...hat.com>,
        Kyle Mahlkuch <Kyle.Mahlkuch@....com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jike Song <jike.song@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Arvind Yadav <arvind.yadav.cs@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Kirti Wankhede <kwankhede@...dia.com>,
        Mauricio Faria de Oliveira <mauricfo@...ux.vnet.ibm.com>,
        Neo Jia <cjia@...dia.com>, Paul Mackerras <paulus@...ba.org>,
        Vlad Tsyrklevich <vlad@...rklevich.net>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v5 1/5] iommu: Add capabilities to a group

On Mon, Aug 07, 2017 at 05:25:44PM +1000, Alexey Kardashevskiy wrote:
> This introduces capabilities to IOMMU groups. The first defined
> capability is IOMMU_GROUP_CAP_ISOLATE_MSIX which tells the IOMMU
> group users that a particular IOMMU group is capable of MSIX message
> filtering; this is useful when deciding whether or not to allow mapping
> of MSIX table to the userspace. Various architectures will enable it
> when they decide that it is safe to do so.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>

Reviewed-by: David Gibson <david@...son.dropbear.id.au>

This seems like a reasonable concept that's probably useful for
something, whether or not it's the best approach for the problem at
hand.

> ---
>  include/linux/iommu.h | 20 ++++++++++++++++++++
>  drivers/iommu/iommu.c | 28 ++++++++++++++++++++++++++++
>  2 files changed, 48 insertions(+)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 2cb54adc4a33..6b6f3c2f4904 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -155,6 +155,9 @@ struct iommu_resv_region {
>  	enum iommu_resv_type	type;
>  };
>  
> +/* IOMMU group capabilities */
> +#define IOMMU_GROUP_CAP_ISOLATE_MSIX		(1U)
> +
>  #ifdef CONFIG_IOMMU_API
>  
>  /**
> @@ -312,6 +315,11 @@ extern void *iommu_group_get_iommudata(struct iommu_group *group);
>  extern void iommu_group_set_iommudata(struct iommu_group *group,
>  				      void *iommu_data,
>  				      void (*release)(void *iommu_data));
> +extern void iommu_group_set_caps(struct iommu_group *group,
> +				 unsigned long clearcaps,
> +				 unsigned long setcaps);
> +extern bool iommu_group_is_capable(struct iommu_group *group,
> +				   unsigned long cap);
>  extern int iommu_group_set_name(struct iommu_group *group, const char *name);
>  extern int iommu_group_add_device(struct iommu_group *group,
>  				  struct device *dev);
> @@ -513,6 +521,18 @@ static inline void iommu_group_set_iommudata(struct iommu_group *group,
>  {
>  }
>  
> +static inline void iommu_group_set_caps(struct iommu_group *group,
> +					unsigned long clearcaps,
> +					unsigned long setcaps)
> +{
> +}
> +
> +static inline bool iommu_group_is_capable(struct iommu_group *group,
> +					  unsigned long cap)
> +{
> +	return false;
> +}
> +
>  static inline int iommu_group_set_name(struct iommu_group *group,
>  				       const char *name)
>  {
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 3f6ea160afed..6b2c34fe2c3d 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -52,6 +52,7 @@ struct iommu_group {
>  	void (*iommu_data_release)(void *iommu_data);
>  	char *name;
>  	int id;
> +	unsigned long caps;
>  	struct iommu_domain *default_domain;
>  	struct iommu_domain *domain;
>  };
> @@ -447,6 +448,33 @@ void iommu_group_set_iommudata(struct iommu_group *group, void *iommu_data,
>  EXPORT_SYMBOL_GPL(iommu_group_set_iommudata);
>  
>  /**
> + * iommu_group_set_caps - Change the group capabilities
> + * @group: the group
> + * @clearcaps: capabilities mask to remove
> + * @setcaps: capabilities mask to add
> + *
> + * IOMMU groups can be capable of various features which device drivers
> + * may read and adjust the behavior.
> + */
> +void iommu_group_set_caps(struct iommu_group *group,
> +		unsigned long clearcaps, unsigned long setcaps)
> +{
> +	group->caps &= ~clearcaps;
> +	group->caps |= setcaps;
> +}
> +EXPORT_SYMBOL_GPL(iommu_group_set_caps);
> +
> +/**
> + * iommu_group_is_capable - Returns if a group capability is present
> + * @group: the group
> + */
> +bool iommu_group_is_capable(struct iommu_group *group, unsigned long cap)
> +{
> +	return !!(group->caps & cap);
> +}
> +EXPORT_SYMBOL_GPL(iommu_group_is_capable);
> +
> +/**
>   * iommu_group_set_name - set name for a group
>   * @group: the group
>   * @name: name

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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