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From: Christoph Hellwig <hch@infradead.org>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>,
	Joerg Roedel <joro@8bytes.org>,
	kevin.tian@intel.com, ashok.raj@intel.com, dima@arista.com,
	tmurphy@arista.com, linux-kernel@vger.kernel.org,
	iommu@lists.linux-foundation.org, jacob.jun.pan@intel.com
Subject: Re: [PATCH v3 5/8] iommu/vt-d: Implement def_domain_type iommu ops entry
Date: Mon, 29 Apr 2019 13:03:38 -0700	[thread overview]
Message-ID: <20190429200338.GA8412@infradead.org> (raw)
In-Reply-To: <20190429020925.18136-6-baolu.lu@linux.intel.com>

> @@ -3631,35 +3607,30 @@ static int iommu_no_mapping(struct device *dev)
>  	if (iommu_dummy(dev))
>  		return 1;
>  
> -	if (!iommu_identity_mapping)
> -		return 0;
> -

FYI, iommu_no_mapping has been refactored in for-next:

https://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu.git/commit/?h=x86/vt-d&id=48b2c937ea37a3bece0094b46450ed5267525289

>  	found = identity_mapping(dev);
>  	if (found) {
> +		/*
> +		 * If the device's dma_mask is less than the system's memory
> +		 * size then this is not a candidate for identity mapping.
> +		 */
> +		u64 dma_mask = *dev->dma_mask;
> +
> +		if (dev->coherent_dma_mask &&
> +		    dev->coherent_dma_mask < dma_mask)
> +			dma_mask = dev->coherent_dma_mask;
> +
> +		if (dma_mask < dma_get_required_mask(dev)) {

I know this is mostly existing code moved around, but it really needs
some fixing.  For one dma_get_required_mask is supposed to return the
required to not bounce mask for the given device.  E.g. for a device
behind an iommu it should always just return 32-bit.  If you really
want to check vs system memory please call dma_direct_get_required_mask
without the dma_ops indirection.

Second I don't even think we need to check the coherent_dma_mask,
dma_direct is pretty good at always finding memory even without
an iommu.

Third this doesn't take take the bus_dma_mask into account.

This probably should just be:

		if (min(*dev->dma_mask, dev->bus_dma_mask) <
		    dma_direct_get_required_mask(dev)) {

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Lu Baolu <baolu.lu@linux.intel.com>
Cc: kevin.tian@intel.com, ashok.raj@intel.com, dima@arista.com,
	tmurphy@arista.com, linux-kernel@vger.kernel.org,
	iommu@lists.linux-foundation.org, jacob.jun.pan@intel.com,
	David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH v3 5/8] iommu/vt-d: Implement def_domain_type iommu ops entry
Date: Mon, 29 Apr 2019 13:03:38 -0700	[thread overview]
Message-ID: <20190429200338.GA8412@infradead.org> (raw)
Message-ID: <20190429200338.mxaBN8YdIdfAhrvlM2nq5SUqI2W6-qf5ip6xE9zChPk@z> (raw)
In-Reply-To: <20190429020925.18136-6-baolu.lu@linux.intel.com>

> @@ -3631,35 +3607,30 @@ static int iommu_no_mapping(struct device *dev)
>  	if (iommu_dummy(dev))
>  		return 1;
>  
> -	if (!iommu_identity_mapping)
> -		return 0;
> -

FYI, iommu_no_mapping has been refactored in for-next:

https://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu.git/commit/?h=x86/vt-d&id=48b2c937ea37a3bece0094b46450ed5267525289

>  	found = identity_mapping(dev);
>  	if (found) {
> +		/*
> +		 * If the device's dma_mask is less than the system's memory
> +		 * size then this is not a candidate for identity mapping.
> +		 */
> +		u64 dma_mask = *dev->dma_mask;
> +
> +		if (dev->coherent_dma_mask &&
> +		    dev->coherent_dma_mask < dma_mask)
> +			dma_mask = dev->coherent_dma_mask;
> +
> +		if (dma_mask < dma_get_required_mask(dev)) {

I know this is mostly existing code moved around, but it really needs
some fixing.  For one dma_get_required_mask is supposed to return the
required to not bounce mask for the given device.  E.g. for a device
behind an iommu it should always just return 32-bit.  If you really
want to check vs system memory please call dma_direct_get_required_mask
without the dma_ops indirection.

Second I don't even think we need to check the coherent_dma_mask,
dma_direct is pretty good at always finding memory even without
an iommu.

Third this doesn't take take the bus_dma_mask into account.

This probably should just be:

		if (min(*dev->dma_mask, dev->bus_dma_mask) <
		    dma_direct_get_required_mask(dev)) {
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2019-04-29 20:03 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-29  2:09 [PATCH v3 0/8] iommu/vt-d: Delegate DMA domain to generic iommu Lu Baolu
2019-04-29  2:09 ` Lu Baolu
2019-04-29  2:09 ` [PATCH v3 1/8] iommu: Add ops entry for supported default domain type Lu Baolu
2019-04-29  2:09   ` Lu Baolu
2019-05-06 15:32   ` Tom Murphy via iommu
2019-05-06 15:32     ` Tom Murphy
2019-05-07 10:28     ` Robin Murphy
2019-05-07 10:28       ` Robin Murphy
2019-05-09  2:30       ` Lu Baolu
2019-05-09  2:30         ` Lu Baolu
2019-05-09 16:11         ` Robin Murphy
2019-05-09 16:11           ` Robin Murphy
2019-05-10  5:29           ` Lu Baolu
2019-05-10  5:29             ` Lu Baolu
2019-05-09  2:22     ` Lu Baolu
2019-05-09  2:22       ` Lu Baolu
2019-04-29  2:09 ` [PATCH v3 2/8] iommu/vt-d: Implement apply_resv_region iommu ops entry Lu Baolu
2019-04-29  2:09   ` Lu Baolu
2019-04-29  2:09 ` [PATCH v3 3/8] iommu/vt-d: Expose ISA direct mapping region via iommu_get_resv_regions Lu Baolu
2019-04-29  2:09   ` Lu Baolu
2019-04-29  2:09 ` [PATCH v3 4/8] iommu/vt-d: Enable DMA remapping after rmrr mapped Lu Baolu
2019-04-29  2:09   ` Lu Baolu
2019-04-29  2:09 ` [PATCH v3 5/8] iommu/vt-d: Implement def_domain_type iommu ops entry Lu Baolu
2019-04-29  2:09   ` Lu Baolu
2019-04-29 20:03   ` Christoph Hellwig [this message]
2019-04-29 20:03     ` Christoph Hellwig
2019-04-30  2:11     ` Lu Baolu
2019-04-30  2:11       ` Lu Baolu
2019-05-06 15:25       ` Tom Murphy via iommu
2019-05-06 15:25         ` Tom Murphy
2019-05-09  4:31         ` Lu Baolu
2019-05-09  4:31           ` Lu Baolu
2019-04-29  2:09 ` [PATCH v3 6/8] iommu/vt-d: Allow DMA domains to be allocated by iommu ops Lu Baolu
2019-04-29  2:09   ` Lu Baolu
2019-04-29  2:09 ` [PATCH v3 7/8] iommu/vt-d: Remove lazy allocation of domains Lu Baolu
2019-04-29  2:09   ` Lu Baolu
2019-04-29  2:09 ` [PATCH v3 8/8] iommu/vt-d: Implement is_attach_deferred iommu ops entry Lu Baolu
2019-04-29  2:09   ` Lu Baolu

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