linux-kernel - [PATCH v3 4/6] vfio: type1: replace domain wide protection flags with supported capabilities

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Message-ID: <022C7612790E20489F80A6F0D54B849F3B2C11AD@EXDAG0-B1.intra.cea.fr>
Date:	Thu, 29 Jan 2015 12:24:14 +0000
From:	GAUGUEY Rémy 228890 <remy.gauguey@....fr>
To:	Antonios Motakis <a.motakis@...tualopensystems.com>,
	"kvmarm@...ts.cs.columbia.edu" <kvmarm@...ts.cs.columbia.edu>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"alex.williamson@...hat.com" <alex.williamson@...hat.com>
CC:	"open list:VFIO DRIVER" <kvm@...r.kernel.org>,
	"will.deacon@....com" <will.deacon@....com>,
	open list <linux-kernel@...r.kernel.org>,
	"tech@...tualopensystems.com" <tech@...tualopensystems.com>
Subject: [PATCH v3 4/6] vfio: type1: replace domain wide protection flags
 with supported capabilities

Hi Antonios, 

On Thu, 27 Nov 2014 18:22:53 Antonios Motakis wrote:
>VFIO_IOMMU_TYPE1 keeps track for each domain it knows a list of protection
>flags it always applies to all mappings in the domain. This is used for
>domains that support IOMMU_CAP_CACHE_COHERENCY.
>
>Refactor this slightly, by keeping track instead that a given domain
>supports the capability, and applying the IOMMU_CACHE protection flag when
>doing the actual DMA mappings.
>
>This will allow us to reuse the behavior for IOMMU_CAP_NOEXEC, which we
>also want to keep track of, but without applying it to all domains that
>support it unless the user explicitly requests it.
>
>Signed-off-by: Antonios Motakis <a.motakis@...xxxxxxxxxxxxxxxxxxx>
>---
> drivers/vfio/vfio_iommu_type1.c | 25 +++++++++++++++++--------
> 1 file changed, 17 insertions(+), 8 deletions(-)
>
>diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
>index 4a9d666..c54dab8 100644
>--- a/drivers/vfio/vfio_iommu_type1.c
>+++ b/drivers/vfio/vfio_iommu_type1.c
> 			if (ret)
> 				return ret;
> 
>@@ -731,7 +740,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
> 	}
> 
> 	if (iommu_capable(bus, IOMMU_CAP_CACHE_COHERENCY))
>-		domain->prot |= IOMMU_CACHE;
>+		domain->caps |= IOMMU_CAP_CACHE_COHERENCY;

IMHO this is not good since IOMMU_CAP_CACHE_COHERENCY is not a bitfield but an enum 
See include/linux/iommu.h 
enum iommu_cap {
	IOMMU_CAP_CACHE_COHERENCY,	/* IOMMU can enforce cache coherent DMA
					   transactions */
	IOMMU_CAP_INTR_REMAP,		/* IOMMU supports interrupt isolation */
	IOMMU_CAP_NOEXEC,		/* IOMMU_NOEXEC flag */
};
One possible fix would to redefine the enum with values with bitfiled values
enum iommu_cap {
	IOMMU_CAP_CACHE_COHERENCY = 1, /* IOMMU can enforce cache coherent DMA
					   transactions */
	IOMMU_CAP_INTR_REMAP = 2,	/* IOMMU supports interrupt isolation */
	IOMMU_CAP_NOEXEC = 4,		/* IOMMU_NOEXEC flag */
};

Regards
Rémy

>_______________________________________________
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>kvmarm@...xxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm

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