Re: [PATCH] Allow acpi-tmr size=2

[Michael Tokarev]

13.07.2020 15:17, Michael S. Tsirkin пишет:
> On Mon, Jul 13, 2020 at 12:46:00PM +0100, Simon John wrote:
>> I don't profess to understand most of this, I am just a user who found
>> something didn't work and tracked down the cause with help from the people
>> on the bugtracker.
>>
>> the min=1 and max=4 was chosen as it seems to be set that way in most other
>> places in the source, and 2 fits in that range.
>>
>> so as macos seems to require 2 bytes but spec says 4 (32 bits) would it be
>> better to set min=2 max=4, given that the original revert seems to be a
>> security fix?

It's not about the security fix, it's about the piece in qemu code which
behaved wrongly for several years, which finally started to actually work.

>> this works equally well:
>>
>> static const MemoryRegionOps acpi_pm_tmr_ops = {
>>     .read = acpi_pm_tmr_read,
>>     .write = acpi_pm_tmr_write,
>>     .valid.min_access_size = 2,
>>     .valid.max_access_size = 4,
>>     .endianness = DEVICE_LITTLE_ENDIAN,
>> };
>>
>> regards.
>>
> 
> Sounds good. And how about also adding:

What this call will receive on a real HW? returning the same 4 bytes
even when asked for 2 smells wrong, no?

>       .impl.min_access_size = 4,

What does it mean? :)

/mjt