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On HP zx1 machines, the 'machvec=dig' parameter is needed for the kdump kernel to avoid problems with the HP sba iommu. The problem is that during the boot of the kdump kernel, the iommu is re-initialized, so in-flight DMA from improperly shutdown drivers causes an IOTLB miss which leads to an MCA. With kdump, the idea is to get into the kdump kernel with as little code as we can, so shutting down drivers properly is not an option. The workaround is to add 'machvec=dig' to the kdump kernel boot parameters. This makes the kdump kernel avoid using the sba iommu altogether, leaving the IOTLB intact. Any ongoing DMA falls harmlessly outside the kdump kernel. After the kdump kernel reboots, all devices will have been shutdown properly and DMA stopped. This patch pushes that functionality into the sba iommu initialization code, so that users won't have to find the obscure documentation telling them about 'machvec=dig'. This patch only affects HP platforms. It still includes one extern declaration in the file, because no applicable header file exists. Signed-off-by: Terry Loftin <terry.loftin@hp.com> Signed-off-by: Alex Williamson <alex.williamson@hp.com> Signed-off-by: Tony Luck <tony.luck@intel.com> |
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