tree 31947fd522227828bfc487af6838adfe2d3cc7fd
parent af731be31279c5f98530cf5af121e08b09af7f95
author Raphael Gault <raphael.gault@arm.com> 1587663521 +0100
committer Will Deacon <will@kernel.org> 1587747591 +0100

Add emulation for CFI compatible flash memory

The EDK II UEFI firmware implementation requires some storage for the EFI
variables, which is typically some flash storage.
Since this is already supported on the EDK II side, we add a CFI flash
emulation to kvmtool.
This is backed by a file, specified via the --flash or -F command line
option. Any flash writes done by the guest will immediately be reflected
into this file (kvmtool mmap's the file).
The flash will be limited to the nearest power-of-2 size, so only the
first 2 MB of a 3 MB file will be used.

This implements a CFI flash using the "Intel/Sharp extended command
set", as specified in:
- JEDEC JESD68.01
- JEDEC JEP137B
- Intel Application Note 646
Some gaps in those specs have been filled by looking at real devices and
other implementations (QEMU, Linux kernel driver).

At the moment this relies on DT to advertise the base address of the
flash memory (mapped into the MMIO address space) and is only enabled
for ARM/ARM64. The emulation itself is architecture agnostic, though.

This is one missing piece toward a working UEFI boot with kvmtool on
ARM guests, the other is to provide writable PCI BARs, which is WIP.

Tested-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Raphael Gault <raphael.gault@arm.com>
[Andre: rewriting and fixing]
Signed-off-by: Andre Przywra <andre.przywara@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>