Re: [PATCH] x86: fix problems due to use of "outb" to port 80 on some AMD64x2 laptops, etc.

Rene Herman wrote:

I hope this is considered half-way correct/sane (note by the way that it's not a good idea to switch a "native_io_delay_port" value since plugging in a variable port would clobber register dx for every outb_p, which would then have to be reloaded for the next outb again). Comments appreciated.

That actually wouldn't be that big of a deal. Switching values in and out of registers is dirt cheap (and MUCH cheaper than an indirect function call) -- of course, if there is a reason to do it for paravirtualization then that's fine; we're talking about something that makes even the slowest CPU operation look speedy anyhow.

If in*_p and out*_p are out-of-lined then %dx would be dead anyway, and so there is even less reason to deal with it.

In theory we could use an alternatives section and patch the instruction, too; seems like way overkill, though.

Note, however, that your code doesn't deal with io_delay()'s in the boot code (arch/x86/boot) at all, nor (obviously) io_delay()'s in boot loaders. In the boot code, access to DMI data is NOT available (we can't even use the INT 15h mover if we want to continue to support Loadlin.)

In the boot code, io_delay() is used to slow down accesses to the KBC, interrupt controller, INT13h logic, and the NMI gate, and to provide a fixed delay during A20 stabilization.

	-hpa
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• Follow-Ups:
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