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From: Jerry Snitselaar <jsnitsel@redhat.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: Filippo Sironi <sironi@amazon.de>,
	iommu@lists.linux-foundation.org, jroedel@suse.de
Subject: Re: [PATCH 3/6] iommu/amd: Take domain->lock for complete attach/detach path
Date: Wed, 25 Sep 2019 23:34:40 -0700
Message-ID: <20190926063440.fvbq37qvqk7ukizf@cantor> (raw)
In-Reply-To: <20190925132300.3038-4-joro@8bytes.org>

On Wed Sep 25 19, Joerg Roedel wrote:
>From: Joerg Roedel <jroedel@suse.de>
>
>The code-paths before __attach_device() and __detach_device() are called
>also access and modify domain state, so take the domain lock there too.
>This allows to get rid of the __detach_device() function.
>
>Fixes: 92d420ec028d ("iommu/amd: Relax locking in dma_ops path")
>Signed-off-by: Joerg Roedel <jroedel@suse.de>
>---
> drivers/iommu/amd_iommu.c | 65 ++++++++++++++++-----------------------
> 1 file changed, 26 insertions(+), 39 deletions(-)
>
>diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
>index 37a9c04fc728..2919168577ff 100644
>--- a/drivers/iommu/amd_iommu.c
>+++ b/drivers/iommu/amd_iommu.c
>@@ -2079,27 +2079,13 @@ static void do_detach(struct iommu_dev_data *dev_data)
> static int __attach_device(struct iommu_dev_data *dev_data,
> 			   struct protection_domain *domain)
> {
>-	unsigned long flags;
>-	int ret;
>-
>-	/* lock domain */
>-	spin_lock_irqsave(&domain->lock, flags);
>-
>-	ret = -EBUSY;
> 	if (dev_data->domain != NULL)
>-		goto out_unlock;
>+		return -EBUSY;
>
> 	/* Attach alias group root */
> 	do_attach(dev_data, domain);
>
>-	ret = 0;
>-
>-out_unlock:
>-
>-	/* ready */
>-	spin_unlock_irqrestore(&domain->lock, flags);
>-
>-	return ret;
>+	return 0;
> }
>
>
>@@ -2181,8 +2167,11 @@ static int attach_device(struct device *dev,
> {
> 	struct pci_dev *pdev;
> 	struct iommu_dev_data *dev_data;
>+	unsigned long flags;
> 	int ret;
>
>+	spin_lock_irqsave(&domain->lock, flags);
>+
> 	dev_data = get_dev_data(dev);
>
> 	if (!dev_is_pci(dev))
>@@ -2190,12 +2179,13 @@ static int attach_device(struct device *dev,
>
> 	pdev = to_pci_dev(dev);
> 	if (domain->flags & PD_IOMMUV2_MASK) {
>+		ret = -EINVAL;
> 		if (!dev_data->passthrough)
>-			return -EINVAL;
>+			goto out;
>
> 		if (dev_data->iommu_v2) {
> 			if (pdev_iommuv2_enable(pdev) != 0)
>-				return -EINVAL;
>+				goto out;
>
> 			dev_data->ats.enabled = true;
> 			dev_data->ats.qdep    = pci_ats_queue_depth(pdev);
>@@ -2219,24 +2209,10 @@ static int attach_device(struct device *dev,
>
> 	domain_flush_complete(domain);
>
>-	return ret;
>-}
>-
>-/*
>- * Removes a device from a protection domain (unlocked)
>- */
>-static void __detach_device(struct iommu_dev_data *dev_data)
>-{
>-	struct protection_domain *domain;
>-	unsigned long flags;
>-
>-	domain = dev_data->domain;
>-
>-	spin_lock_irqsave(&domain->lock, flags);
>-
>-	do_detach(dev_data);
>-
>+out:
> 	spin_unlock_irqrestore(&domain->lock, flags);
>+
>+	return ret;
> }
>
> /*
>@@ -2246,10 +2222,13 @@ static void detach_device(struct device *dev)
> {
> 	struct protection_domain *domain;
> 	struct iommu_dev_data *dev_data;
>+	unsigned long flags;
>
> 	dev_data = get_dev_data(dev);
> 	domain   = dev_data->domain;
>
>+	spin_lock_irqsave(&domain->lock, flags);
>+
> 	/*
> 	 * First check if the device is still attached. It might already
> 	 * be detached from its domain because the generic
>@@ -2257,12 +2236,12 @@ static void detach_device(struct device *dev)
> 	 * our alias handling.
> 	 */
> 	if (WARN_ON(!dev_data->domain))
>-		return;
>+		goto out;
>
>-	__detach_device(dev_data);
>+	do_detach(dev_data);
>
> 	if (!dev_is_pci(dev))
>-		return;
>+		goto out;
>
> 	if (domain->flags & PD_IOMMUV2_MASK && dev_data->iommu_v2)
> 		pdev_iommuv2_disable(to_pci_dev(dev));
>@@ -2270,6 +2249,9 @@ static void detach_device(struct device *dev)
> 		pci_disable_ats(to_pci_dev(dev));
>
> 	dev_data->ats.enabled = false;
>+
>+out:
>+	spin_unlock_irqrestore(&domain->lock, flags);
> }
>
> static int amd_iommu_add_device(struct device *dev)
>@@ -2904,13 +2886,18 @@ int __init amd_iommu_init_dma_ops(void)
> static void cleanup_domain(struct protection_domain *domain)
> {
> 	struct iommu_dev_data *entry;
>+	unsigned long flags;
>+
>+	spin_lock_irqsave(&domain->lock, flags);
>
> 	while (!list_empty(&domain->dev_list)) {
> 		entry = list_first_entry(&domain->dev_list,
> 					 struct iommu_dev_data, list);
> 		BUG_ON(!entry->domain);
>-		__detach_device(entry);
>+		do_detach(entry);
> 	}
>+
>+	spin_unlock_irqrestore(&domain->lock, flags);
> }
>
> static void protection_domain_free(struct protection_domain *domain)
>-- 
>2.17.1
>
>_______________________________________________
>iommu mailing list
>iommu@lists.linux-foundation.org
>https://lists.linuxfoundation.org/mailman/listinfo/iommu

Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>

_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  parent reply index

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-25 13:22 [PATCH 0/6] iommu/amd: Locking Fixes Joerg Roedel
2019-09-25 13:22 ` [PATCH 1/6] iommu/amd: Remove domain->updated Joerg Roedel
2019-09-25 15:45   ` Sironi, Filippo via iommu
2019-09-26  6:18   ` Jerry Snitselaar
2019-09-25 13:22 ` [PATCH 2/6] iommu/amd: Remove amd_iommu_devtable_lock Joerg Roedel
2019-09-25 15:50   ` Sironi, Filippo via iommu
2019-09-25 15:52     ` Sironi, Filippo via iommu
2019-09-26  6:24   ` Jerry Snitselaar
2019-09-25 13:22 ` [PATCH 3/6] iommu/amd: Take domain->lock for complete attach/detach path Joerg Roedel
2019-09-25 15:53   ` Sironi, Filippo via iommu
2019-09-26  6:34   ` Jerry Snitselaar [this message]
2019-09-25 13:22 ` [PATCH 4/6] iommu/amd: Check for busy devices earlier in attach_device() Joerg Roedel
2019-09-25 15:55   ` Sironi, Filippo via iommu
2019-09-26  6:37   ` Jerry Snitselaar
2019-09-25 13:22 ` [PATCH 5/6] iommu/amd: Lock dev_data in attach/detach code paths Joerg Roedel
2019-09-25 15:56   ` Sironi, Filippo via iommu
2019-09-26  6:41   ` Jerry Snitselaar
2019-09-25 13:23 ` [PATCH 6/6] iommu/amd: Lock code paths traversing protection_domain->dev_list Joerg Roedel
2019-09-25 15:58   ` Sironi, Filippo via iommu
2019-09-26  6:48   ` Jerry Snitselaar
2019-09-26  0:25 ` [PATCH 0/6] iommu/amd: Locking Fixes Jerry Snitselaar
2019-09-26  5:46   ` Joerg Roedel

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