linux-kernel - Re: [RFC v3 02/15] vfio: expose MSI mapping requirement through VFIO_IOMMU_GET

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Message-ID: <20160218093454.660b20c6@arm.com>
Date:	Thu, 18 Feb 2016 09:34:54 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Eric Auger <eric.auger@...aro.org>
Cc:	eric.auger@...com, alex.williamson@...hat.com, will.deacon@....com,
	joro@...tes.org, tglx@...utronix.de, jason@...edaemon.net,
	christoffer.dall@...aro.org, linux-arm-kernel@...ts.infradead.org,
	kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
	suravee.suthikulpanit@....com, patches@...aro.org,
	linux-kernel@...r.kernel.org, Manish.Jaggi@...iumnetworks.com,
	Bharat.Bhushan@...escale.com, pranav.sawargaonkar@...il.com,
	p.fedin@...sung.com, iommu@...ts.linux-foundation.org,
	sherry.hurwitz@....com, brijesh.singh@....com, leo.duran@....com,
	Thomas.Lendacky@....com
Subject: Re: [RFC v3 02/15] vfio: expose MSI mapping requirement through
 VFIO_IOMMU_GET_INFO

On Fri, 12 Feb 2016 08:13:04 +0000
Eric Auger <eric.auger@...aro.org> wrote:

> This patch allows the user-space to retrieve whether msi write
> transaction addresses must be mapped. This is returned through the
> VFIO_IOMMU_GET_INFO API and its new flag: VFIO_IOMMU_INFO_REQUIRE_MSI_MAP.
> 
> Signed-off-by: Bharat Bhushan <Bharat.Bhushan@...escale.com>
> Signed-off-by: Eric Auger <eric.auger@...aro.org>
> 
> ---
> 
> RFC v1 -> v1:
> - derived from
>   [RFC PATCH 3/6] vfio: Extend iommu-info to return MSIs automap state
> - renamed allow_msi_reconfig into require_msi_mapping
> - fixed VFIO_IOMMU_GET_INFO
> ---
>  drivers/vfio/vfio_iommu_type1.c | 26 ++++++++++++++++++++++++++
>  include/uapi/linux/vfio.h       |  1 +
>  2 files changed, 27 insertions(+)
> 
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 6f1ea3d..c5b57e1 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -255,6 +255,29 @@ static int vaddr_get_pfn(unsigned long vaddr, int prot, unsigned long *pfn)
>  }
>  
>  /*
> + * vfio_domains_require_msi_mapping: indicates whether MSI write transaction
> + * addresses must be mapped
> + *
> + * returns true if it does
> + */
> +static bool vfio_domains_require_msi_mapping(struct vfio_iommu *iommu)
> +{
> +	struct vfio_domain *d;
> +	bool ret;
> +
> +	mutex_lock(&iommu->lock);
> +	/* All domains have same require_msi_map property, pick first */
> +	d = list_first_entry(&iommu->domain_list, struct vfio_domain, next);
> +	if (iommu_domain_get_attr(d->domain, DOMAIN_ATTR_MSI_MAPPING, NULL) < 0)
> +		ret = false;
> +	else
> +		ret = true;

nit: this could be simplified as:

ret = (iommu_domain_get_attr(d->domain, DOMAIN_ATTR_MSI_MAPPING, NULL) == 0);

> +	mutex_unlock(&iommu->lock);
> +
> +	return ret;
> +}
> +
> +/*
>   * Attempt to pin pages.  We really don't want to track all the pfns and
>   * the iommu can only map chunks of consecutive pfns anyway, so get the
>   * first page and all consecutive pages with the same locking.
> @@ -997,6 +1020,9 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
>  
>  		info.flags = VFIO_IOMMU_INFO_PGSIZES;
>  
> +		if (vfio_domains_require_msi_mapping(iommu))
> +			info.flags |= VFIO_IOMMU_INFO_REQUIRE_MSI_MAP;
> +
>  		info.iova_pgsizes = vfio_pgsize_bitmap(iommu);
>  
>  		return copy_to_user((void __user *)arg, &info, minsz);
> diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
> index 7d7a4c6..43e183b 100644
> --- a/include/uapi/linux/vfio.h
> +++ b/include/uapi/linux/vfio.h
> @@ -400,6 +400,7 @@ struct vfio_iommu_type1_info {
>  	__u32	argsz;
>  	__u32	flags;
>  #define VFIO_IOMMU_INFO_PGSIZES (1 << 0)	/* supported page sizes info */
> +#define VFIO_IOMMU_INFO_REQUIRE_MSI_MAP (1 << 1)/* MSI must be mapped */
>  	__u64	iova_pgsizes;		/* Bitmap of supported page sizes */
>  };
>  


FWIW:

Acked-by: Marc Zyngier <marc.zyngier@....com>

	M.
-- 
Jazz is not dead. It just smells funny.