linux-kernel - Re: [regression]2.6.25-rc4: boot panic on alpha

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Date:	Fri, 7 Mar 2008 19:21:16 +0300
From:	Ivan Kokshaysky <ink@...assic.park.msu.ru>
To:	FUJITA Tomonori <tomof@....org>
Cc:	rct@...s.com, mingo@...e.hu, linux-kernel@...r.kernel.org,
	linux-alpha@...r.kernel.org, fujita.tomonori@....ntt.co.jp,
	akpm@...ux-foundation.org
Subject: Re: [regression]2.6.25-rc4: boot panic on alpha

On Fri, Mar 07, 2008 at 11:56:40PM +0900, FUJITA Tomonori wrote:
> Very sorry, I probably broke the IOMMU. I don't have the hardware so
> I've not tested the patches.

Unfortunately, I was not able to test these patches either, as my
alpha with iommmu and scsi is disassembled at the moment, thanks to
dead CPU fan...

> -	BUG_ON(arena->dma_base & ~PAGE_MASK);
> +	if (arena->dma_base & ~PAGE_MASK)
> +		printk("%s %d: %lx\n", __FUNCTION__, __LINE__, arena->dma_base);

arena->dma_base is always properly aligned - it's pretty fundamental thing.

>  	base = arena->dma_base >> PAGE_SHIFT;
>  	if (dev)
>  		boundary_size = ALIGN(dma_get_max_seg_size(dev) + 1, PAGE_SIZE)
				      ^^^^^^^^^^^^^^^^^^^^^^^^^
Must be dma_get_seg_boundary(dev). Hopefully it's the only typo ;-)

> @@ -152,7 +155,8 @@ iommu_arena_find_pages(struct device *dev, struct pci_iommu_arena *arena,
>  	else
>  		boundary_size = ALIGN(1UL << 32, PAGE_SIZE) >> PAGE_SHIFT;

A bit of abuse of ALIGN() macro, to my taste ;-)

> -	BUG_ON(!is_power_of_2(boundary_size));
> +	if (!is_power_of_2(boundary_size))
> +		printk("%s %d: %lx\n", __FUNCTION__, __LINE__, boundary_size);

Perhaps it was that, if the scsi driver set max_seg_size to something
other than default 65536 (and not a power of two)...

Bob, can you give it a try?

Ivan.

diff --git a/arch/alpha/kernel/pci_iommu.c b/arch/alpha/kernel/pci_iommu.c
index be6fa10..e07a23f 100644
--- a/arch/alpha/kernel/pci_iommu.c
+++ b/arch/alpha/kernel/pci_iommu.c
@@ -144,15 +144,14 @@ iommu_arena_find_pages(struct device *dev, struct pci_iommu_arena *arena,
 	unsigned long base;
 	unsigned long boundary_size;
 
-	BUG_ON(arena->dma_base & ~PAGE_MASK);
 	base = arena->dma_base >> PAGE_SHIFT;
-	if (dev)
-		boundary_size = ALIGN(dma_get_max_seg_size(dev) + 1, PAGE_SIZE)
-			>> PAGE_SHIFT;
-	else
-		boundary_size = ALIGN(1UL << 32, PAGE_SIZE) >> PAGE_SHIFT;
-
-	BUG_ON(!is_power_of_2(boundary_size));
+	if (dev) {
+		boundary_size = dma_get_seg_boundary(dev) + 1;
+		BUG_ON(!is_power_of_2(boundary_size));
+		boundary_size >>= PAGE_SHIFT;
+	} else {
+		boundary_size = 1UL << (32 - PAGE_SHIFT);
+	}
 
 	/* Search forward for the first mask-aligned sequence of N free ptes */
 	ptes = arena->ptes;
--
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