Re: [PATCH 5/5] powerpc: use the generic dma_ops_bypass mode

[Christoph Hellwig]

On Sun, Aug 30, 2020 at 11:04:21AM +0200, Cédric Le Goater wrote:
> Hello,
> 
> On 7/8/20 5:24 PM, Christoph Hellwig wrote:
> > Use the DMA API bypass mechanism for direct window mappings.  This uses
> > common code and speed up the direct mapping case by avoiding indirect
> > calls just when not using dma ops at all.  It also fixes a problem where
> > the sync_* methods were using the bypass check for DMA allocations, but
> > those are part of the streaming ops.
> > 
> > Note that this patch loses the DMA_ATTR_WEAK_ORDERING override, which
> > has never been well defined, as is only used by a few drivers, which
> > IIRC never showed up in the typical Cell blade setups that are affected
> > by the ordering workaround.
> > 
> > Fixes: efd176a04bef ("powerpc/pseries/dma: Allow SWIOTLB")
> > Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> > ---
> >  arch/powerpc/Kconfig              |  1 +
> >  arch/powerpc/include/asm/device.h |  5 --
> >  arch/powerpc/kernel/dma-iommu.c   | 90 ++++---------------------------
> >  3 files changed, 10 insertions(+), 86 deletions(-)
> 
> I am seeing corruptions on a couple of POWER9 systems (boston) when
> stressed with IO. stress-ng gives some results but I have first seen
> it when compiling the kernel in a guest and this is still the best way
> to raise the issue.
> 
> These systems have of a SAS Adaptec controller :
> 
>   0003:01:00.0 Serial Attached SCSI controller: Adaptec Series 8 12G SAS/PCIe 3 (rev 01)
> 
> When the failure occurs, the POWERPC EEH interrupt fires and dumps
> lowlevel PHB4 registers among which :
> 					  
>   [ 2179.251069490,3] PHB#0003[0:3]:           phbErrorStatus = 0000028000000000
>   [ 2179.251117476,3] PHB#0003[0:3]:      phbFirstErrorStatus = 0000020000000000
> 
> The bits raised identify a PPC 'TCE' error, which means it is related
> to DMAs. See below for more details.
> 
> 
> Reverting this patch "fixes" the issue but it is probably else where,
> in some other layers or in the aacraid driver. How should I proceed 
> to get more information ?

The aacraid DMA masks look like a mess.  Can you try the hack
below and see it it helps?

diff --git a/drivers/scsi/aacraid/aachba.c b/drivers/scsi/aacraid/aachba.c
index 769af4ca9ca97e..79c6b744dbb66c 100644
--- a/drivers/scsi/aacraid/aachba.c
+++ b/drivers/scsi/aacraid/aachba.c
@@ -2228,18 +2228,6 @@ int aac_get_adapter_info(struct aac_dev* dev)
 		expose_physicals = 0;
 	}
 
-	if (dev->dac_support) {
-		if (!pci_set_dma_mask(dev->pdev, DMA_BIT_MASK(64))) {
-			if (!dev->in_reset)
-				dev_info(&dev->pdev->dev, "64 Bit DAC enabled\n");
-		} else if (!pci_set_dma_mask(dev->pdev, DMA_BIT_MASK(32))) {
-			dev_info(&dev->pdev->dev, "DMA mask set failed, 64 Bit DAC disabled\n");
-			dev->dac_support = 0;
-		} else {
-			dev_info(&dev->pdev->dev, "No suitable DMA available\n");
-			rcode = -ENOMEM;
-		}
-	}
 	/*
 	 * Deal with configuring for the individualized limits of each packet
 	 * interface.
diff --git a/drivers/scsi/aacraid/commsup.c b/drivers/scsi/aacraid/commsup.c
index adbdc3b7c7a706..dbb23b351a4e7d 100644
--- a/drivers/scsi/aacraid/commsup.c
+++ b/drivers/scsi/aacraid/commsup.c
@@ -1479,7 +1479,6 @@ static int _aac_reset_adapter(struct aac_dev *aac, int forced, u8 reset_type)
 	struct Scsi_Host *host = aac->scsi_host_ptr;
 	int jafo = 0;
 	int bled;
-	u64 dmamask;
 	int num_of_fibs = 0;
 
 	/*
@@ -1558,22 +1557,7 @@ static int _aac_reset_adapter(struct aac_dev *aac, int forced, u8 reset_type)
 	kfree(aac->fsa_dev);
 	aac->fsa_dev = NULL;
 
-	dmamask = DMA_BIT_MASK(32);
 	quirks = aac_get_driver_ident(index)->quirks;
-	if (quirks & AAC_QUIRK_31BIT)
-		retval = pci_set_dma_mask(aac->pdev, dmamask);
-	else if (!(quirks & AAC_QUIRK_SRC))
-		retval = pci_set_dma_mask(aac->pdev, dmamask);
-	else
-		retval = pci_set_consistent_dma_mask(aac->pdev, dmamask);
-
-	if (quirks & AAC_QUIRK_31BIT && !retval) {
-		dmamask = DMA_BIT_MASK(31);
-		retval = pci_set_consistent_dma_mask(aac->pdev, dmamask);
-	}
-
-	if (retval)
-		goto out;
 
 	if ((retval = (*(aac_get_driver_ident(index)->init))(aac)))
 		goto out;
diff --git a/drivers/scsi/aacraid/linit.c b/drivers/scsi/aacraid/linit.c
index 8588da0a065551..d897a9d59e24a1 100644
--- a/drivers/scsi/aacraid/linit.c
+++ b/drivers/scsi/aacraid/linit.c
@@ -1634,8 +1634,6 @@ static int aac_probe_one(struct pci_dev *pdev, const struct pci_device_id *id)
 	struct list_head *insert = &aac_devices;
 	int error;
 	int unique_id = 0;
-	u64 dmamask;
-	int mask_bits = 0;
 	extern int aac_sync_mode;
 
 	/*
@@ -1658,33 +1656,6 @@ static int aac_probe_one(struct pci_dev *pdev, const struct pci_device_id *id)
 	if (error)
 		goto out;
 
-	if (!(aac_drivers[index].quirks & AAC_QUIRK_SRC)) {
-		error = pci_set_dma_mask(pdev, DMA_BIT_MASK(32));
-		if (error) {
-			dev_err(&pdev->dev, "PCI 32 BIT dma mask set failed");
-			goto out_disable_pdev;
-		}
-	}
-
-	/*
-	 * If the quirk31 bit is set, the adapter needs adapter
-	 * to driver communication memory to be allocated below 2gig
-	 */
-	if (aac_drivers[index].quirks & AAC_QUIRK_31BIT) {
-		dmamask = DMA_BIT_MASK(31);
-		mask_bits = 31;
-	} else {
-		dmamask = DMA_BIT_MASK(32);
-		mask_bits = 32;
-	}
-
-	error = pci_set_consistent_dma_mask(pdev, dmamask);
-	if (error) {
-		dev_err(&pdev->dev, "PCI %d B consistent dma mask set failed\n"
-				, mask_bits);
-		goto out_disable_pdev;
-	}
-
 	pci_set_master(pdev);
 
 	shost = scsi_host_alloc(&aac_driver_template, sizeof(struct aac_dev));