On Fri, Jan 04, 2013 at 02:10:25PM -0800, Yinghai Lu wrote:
> On Fri, Jan 4, 2013 at 1:02 PM, Shuah Khan <shuahk...@gmail.com> wrote:
> > Pani'cing the system doesn't sound like a good option to me in this
> > case. This change to disable swiotlb is made for kdump. However, with
> > this change several system fail to boot, unless crashkernel_low=72M is
> > specified.
>
> this patchset is new feature to put second kdump kernel above 4G.
>
> >
> > I would the say the right approach to solve this would be to not
> > change the current pci_swiotlb_detect_override() behavior and treat
> > swiotlb =1 upon entry equivalent to swiotlb_force set.
>
> that will make intel system have to take crashkernel_low=72M too.
> otherwise intel system will get panic during swiotlb allocation.
Two things:
1). You need to wrap the 'is_enough_..' in CONFIG_KEXEC, which means
that the function needs to go in a header file.
2). The check for 1MB is suspect. Why only 1MB? You mentioned it is
b/c of crashkernel_low=72M (which I am not seeing in v3.8
kernel-parameters.txt?
Is that part of your mega-patchset?). Anyhow, there seems to be a
disconnect -
what if the user supplied crashkernel_low=27M? Perhaps the 'is_enough'
should also parse the bootparams to double-check that there is enough
low-mem space? But then if the kernel grows then 72M might not be enough -
you might need 82M with 3.9.
Perhaps a better way for this is to do:
1). Change 'is_enough' to check only for 4MB.
2). When booting as kexec, the SWIOTLB would only use 4MB instead of
64MB?
Or, we could also use the post-late SWIOTLB initialization similiary to
how it was
done on ia64. This would mean that the AMD VI code would just call the
.. something like this - NOT tested or even compile tested:
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index c1c74e0..e7fa8f7 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -3173,6 +3173,24 @@ int __init amd_iommu_init_dma_ops(void)
if (unhandled && max_pfn > MAX_DMA32_PFN) {
/* There are unhandled devices - initialize swiotlb for them */
swiotlb = 1;
+ /* Late (so no bootmem allocator) usage and only if the early
SWIOTLB
+ * hadn't been allocated (which can happen on kexec kernels
booted
+ * above 4GB). */
+ if (!swiotlb_nr_tbl()) {
+ int retry = 3;
+ int mb_size = 64;
+ int rc = 0;
+retry_me:
+ if (retry < 0)
+ panic("We tried setting %dMB for SWIOTLB but
got -ENOMEM", mb_size << 1);
+ rc = swiotlb_late_init_with_default_size(mb_size *
(1<<20));
+ if (rc) {
+ retry --;
+ mb_size >> 1;
+ goto retry_me;
+ }
+ dma_ops = &swiotlb_dma_ops;
+ }
}
amd_iommu_stats_init();
And then the early SWIOTLB initialization for 64MB can fail and we are still OK.
>
> Thanks
>
> Yinghai
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
