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.
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