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Re: [RFC PATCH] docs/devel: add some notes on tcg-icount for developers
From: |
Paolo Bonzini |
Subject: |
Re: [RFC PATCH] docs/devel: add some notes on tcg-icount for developers |
Date: |
Fri, 19 Jun 2020 17:44:59 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 |
On 19/06/20 16:54, Peter Maydell wrote:
>> +
>> +MMIO isn't the only type of operation for which we might need a
>> +correct and accurate clock. IO port instructions and accesses to
>> +system registers are the common examples here. For the clock to be
>> +accurate you end a translation block on these instructions.
>> +
>> +.. warning:: (CONJECTURE) instructions that won't get trapped in the
>> + io_read/writex shouldn't need gen_io_start/end blocks
>> + around them.
> I think this is backwards -- instructions where icount is handled
> by io_readx/io_writex are the ones that don't need to be marked
> with gen_io_start. It's the i/o instructions that don't go through
> io_readx/io_writex that need gen_io_start.
Yes, and likewise instructions where icount is handled by
io_readx/io_writex need not terminate the TB.
Paolo