Re: [Xen-devel] [PATCH] add support for XCHG instruction accessing APIC

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 4 Apr 2006, at 22:24, Boris Ostrovsky wrote:

> 32-bit SMP Linux uses xchg instruction to access APIC (see
> apic_write_atomic()). Attached is patch that adds support for
> this instruction.
>
> The patch also fixes missed dependencies (in xen/Rules.mk) on
> header files in include/asm-x86/hvm.
I wonder if it is worth adding the locking? xchg is only used to write 
to broken APICs -- the OS does not care about the returned value. The 
APIC is implemented entirely in Xen, so the lock isn't held across an 
ioreq round-trip to qemu-dm, right?
 -- Keir


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