Hi Joerg Roedel,
When we run below command, the kernel message showed below confusing failed
messages:
sudo kexec -l /boot/vmlinuz-4.11.0-rc7
--append=root=UUID=276659dd-77f0-47f9-967c-7643c260b746
--initrd=/boot/initrd.img-4.11.0-rc7
sudo kexec -e
---
[ 0.203397] DMAR-IR: Failed to copy IR table for dmar2 from previous kernel
[ 0.211568] DMAR-IR: Failed to copy IR table for dmar1 from previous
kernel
[ 0.219738] DMAR-IR: Failed to copy IR table for dmar0 from previous
kernel
[ 0.227906] DMAR-IR: Failed to copy IR table for dmar3 from previous
kernel
---
The driver "intel_irq_remapping.c" uses "is_kdump_kernel()" API to
determine whether copy IR table from previous kernel.
a) When booting a kdump kernel specified by "kexec -p" (loading the new
kernel for use on panic), the "is_kdump_kernel()" API is true then the driver
copy IR table from previous kernel.
b) While when booting a new kernel specified by "kexec -l" (loading the
new kernel into current kernel) the "is_kdump_kernel()" API is false then the
driver prints error message "Failed to copy IR table from
previous kernel" directly. It looks like the printk is misleading
and it's nothing actually failed, but just it isn't copying if the new kernel
is not a kdump kernel.
Found that the commit id "af3b358e48115" said:
---
iommu/vt-d: Copy IR table from old kernel when in kdump mode
When we are booting into a kdump kernel and find IR enabled,
copy over the contents of the previous IR table so that
spurious interrupts will not be target aborted.
---
May I ask some questions:
What are spurious interrupts?
For kdump kernel can we just reinitializing IR table(as like normal
kernel boot from power on) to handle the "spurious interrupts" issue instead of
copying IR table from previous kernel?
For booting a new kernel by "kexec -l" (my test case), do we still need
to copy IR table from previous kernel to handle the "spurious interrupts" issue?
Thanks!
qiuxu
BR
qiuxu
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