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Re: [Qemu-devel] [PATCH v3 2/3] target-ppc: add flag in chech_tlb_flush(


From: Nikunj A Dadhania
Subject: Re: [Qemu-devel] [PATCH v3 2/3] target-ppc: add flag in chech_tlb_flush()
Date: Wed, 14 Sep 2016 09:23:05 +0530
User-agent: Notmuch/0.21 (https://notmuchmail.org) Emacs/25.0.94.1 (x86_64-redhat-linux-gnu)

David Gibson <address@hidden> writes:

> [ Unknown signature status ]
> On Mon, Sep 12, 2016 at 11:18:33AM +0530, Nikunj A Dadhania wrote:
>> The flag will be used to indicate whether broadcast tlb flush is needed
>> or not.
>> 
>> Moreover, BookS does both ptesync and tlbsync, so make that a nop for
>> the server and tlbsync would generate a check flush for BookE
>
> This commit message needs a bunch more detail.  The flag indicates
> whether a broadcast tlb flush is neede where exactly?  How does the
> information in the parameter differ from the information in the
> existing flags which check_tlb_flush() checks?

How about the below:

Due to lazy tlb flushes, propagation of the tlb flush is delayed.
Moreover, certain operations need to do broadcast flush, this too can be
delayed until we hit the operation that warrant a broadcast.

Currently, the code only checks if local flush is necessary and does the
local flush. This global flag would inform check_tlb_flush that this
operation needs a broadcast flush. The patch just enables the routine
with the flag, succeeding patch will use this information along with
global_flush flag(set by tlbie/h_remove instruction) to broadcast the
tlb flushes.

Moreover, BookS does both ptesync and tlbsync, so make that a nop for
the server and tlbsync would generate a check flush for BookE

Regards,
Nikunj




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