Re: [PATCH v7u1 26/31] x86: Don't enable swiotlb if there is notenough ram for it

From: Yinghai Lu
Date: Fri Jan 04 2013 - 17:34:24 EST

On Fri, Jan 4, 2013 at 2:26 PM, Shuah Khan <shuahkhan@xxxxxxxxx> wrote:

> However, I think regression on existing behavior with a
> panic is a bit of a big hammer. Thie change causes panic on systems
> even when kdump is not enabled, if I understand it correctly.

I don't think so.

+static bool __init enough_mem_for_swiotlb(void)
+ /* do we have less than 1M RAM under 4G ? */
+ return memblock_mem_size(1ULL<<(32-PAGE_SHIFT)) > (1ULL<<20);

enough_mem_for_swiotlb could return false for them?


int __init pci_swiotlb_detect_override(void)
- int use_swiotlb = swiotlb | swiotlb_force;
if (swiotlb_force)
swiotlb = 1;
+ else if (!enough_mem_for_swiotlb())
+ swiotlb = 0;

- return use_swiotlb;
+ return swiotlb;

it only disable swiotlb when there is less 1M mem under 4G.
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