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This patch allows the user to usefully specify
-drive file=img_1,if=pflash,format=raw,readonly \
-drive file=img_2,if=pflash,format=raw
on the command line. The flash images will be mapped under 4G in their
reverse unit order -- that is, with their base addresses progressing
downwards, in increasing unit order.
(The unit number increases with command line order if not explicitly
specified.)
This accommodates the following use case: suppose that OVMF is split in
two parts, a writeable host file for non-volatile variable storage, and a
read-only part for bootstrap and decompressible executable code.
The binary code part would be read-only, centrally managed on the host
system, and passed in as unit 0. The variable store would be writeable,
VM-specific, and passed in as unit 1.
00000000ffe00000-00000000ffe1ffff (prio 0, R-): system.flash1
00000000ffe20000-00000000ffffffff (prio 0, R-): system.flash0
(If the guest tries to write to the flash range that is backed by the
read-only drive, pflash_update() is never called; various flash
programming/erase errors are returned to the guest instead. See the
callers of pflash_update(), and the initialization of "pfl->ro", in
"hw/block/pflash_cfi01.c".)
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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