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Re: [Qemu-devel] [PATCH v2 1/2] memory: Fix old portio word accesses

From: Avi Kivity
Subject: Re: [Qemu-devel] [PATCH v2 1/2] memory: Fix old portio word accesses
Date: Mon, 19 Sep 2011 15:42:45 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:6.0.2) Gecko/20110906 Thunderbird/6.0.2

On 09/19/2011 03:32 PM, Jan Kiszka wrote:
>  It's opt-in.  If a device sets
>  MemoryRegionOps::impl.{min,max}_access_size = 1, it will only be fed
>  byte accesses (the core will take care of breaking apart larger
>  writes).  If it sets MemoryRegionOps::impl.{min,max}_access_size = 4, it
>  will only get long accesses (and the core will/should shift/mask or
>  RMW).  Refusing illegal access sizes is done using
>  MemoryRegionOps::valid.  Most of this is unimplemented unfortunately.

That makes sense (for non-old_portio users).

The trick of having a way to register N callbacks with one shot is worth growing. Ideally each register in a BAR would have a callback and we'd do something like

    MemoryRegionOps mydev_ops = {
        .registers = {
             { MYDEV_REG_x, 4, 4, mydev_reg_x_read, mydev_reg_x_write, },

with hints to the core like "this register sits at this offset, use it for reads instead of a callback", or, "this is a read-only register".

error compiling committee.c: too many arguments to function

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