Since commit 5d971f9e67 we don't accept mismatching sizes in memory_region_access_valid(). This gives troubles when a device is on an ISA bus, because the CPU is free to use 8/16-bit accesses on the bus (or up to 32-bit on EISA bus), regardless what range is valid for the device.
Add a check to ensure devices plugged on the ISA bus can accept 8/16-bits accesses. Related bug reports: - https://lore.kernel.org/xen-devel/20200630170913.123646-1-anthony.per...@citrix.com/T/ - https://bugs.debian.org/964793 - https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=964247 - https://bugs.launchpad.net/bugs/1886318 Signed-off-by: Philippe Mathieu-Daudé <f4...@amsat.org> --- MST: I really don't like this approach, I think the ISA bus should adjust the access. since v1: only 8/16-bit accesses enforced --- hw/isa/isa-bus.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/hw/isa/isa-bus.c b/hw/isa/isa-bus.c index 58fde178f9..e142eeef06 100644 --- a/hw/isa/isa-bus.c +++ b/hw/isa/isa-bus.c @@ -132,6 +132,20 @@ static inline void isa_init_ioport(ISADevice *dev, uint16_t ioport) void isa_register_ioport(ISADevice *dev, MemoryRegion *io, uint16_t start) { + if (io->ops->valid.min_access_size > 1) { + /* + * To be backward compatible with IBM-PC bus, ISA bus must accept + * 8-bit accesses. + */ + error_report("ISA device '%s' requires I/O min_access_size of 1 (byte)", + object_get_typename(OBJECT(dev))); + exit(1); + } else if (io->ops->valid.max_access_size < 2) { + /* ISA bus must accept 16-bit accesses (EISA accepts 32-bit) */ + error_report("ISA device '%s' requires I/O max_access_size of " + "at least 2 (bytes)", object_get_typename(OBJECT(dev))); + exit(1); + } memory_region_add_subregion(isabus->address_space_io, start, io); isa_init_ioport(dev, start); } -- 2.21.3
