Messages in this thread | | | Date | Thu, 1 Jun 2023 09:57:30 -0700 | Subject | Re: [PATCH v2] iscsi_ibft: Fix finding the iBFT under Xen Dom 0 | From | Dave Hansen <> |
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On 5/30/23 08:01, Ross Lagerwall wrote: > Since firmware doesn't indicate the iBFT in the E820, add a reserved > region so that it gets identity mapped when running as Dom 0 so that it > is possible to search for it. Move the call to reserve_ibft_region() > later so that it is called after the Xen identity mapping adjustments > are applied. > > Finally, instead of using isa_bus_to_virt() which doesn't do the right > thing under Xen, use early_memremap() like the dmi_scan code does.
This is connecting Xen, iSCSI and x86. Some background here would be *really* nice for dummies like me that deal heavily in only one of those three.
One or two sentences like this:
Firmware can provide an iSCSI-specific table called the iBFT which helps the OS boot from iSCSI devices.
can go a long way for dummies like me. As could some background about why this:
... add a reserved region so that it gets identity mapped when running as Dom 0 so that it is possible to search for it.
These are all English words, but off the top of my head, I have no idea why reserved regions get identity mapped when running as Dom 0 or why that makes it possible to search.
The addresses and size here:
> +#ifdef CONFIG_ISCSI_IBFT_FIND > + /* Reserve 0.5 MiB to 1 MiB region so iBFT can be found */ > + xen_e820_table.entries[xen_e820_table.nr_entries].addr = 0x80000; > + xen_e820_table.entries[xen_e820_table.nr_entries].size = 0x80000; > + xen_e820_table.entries[xen_e820_table.nr_entries].type = E820_TYPE_RESERVED; > + xen_e820_table.nr_entries++; > +#endif
also appear to be conjured out of thin air.
As does the move of:
> + reserve_ibft_region();
I'm sure I can go figure this all out with some research. But, I'd really appreciate some extra effort from you in this changelog to save me the time. I bet you can explain it a lot more efficiently than I can go figure it out.
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