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From: Kenneth Lee <Kenneth-Lee-2012@foxmail.com>
To: qemu-devel@nongnu.org
Subject: Does the page boundary check still necessary?
Date: Wed, 15 Feb 2023 16:39:51 +0800	[thread overview]
Message-ID: <tencent_F8004464D432CD4CABBADFE9E9493EDF9607@qq.com> (raw)

Hello,

I hope I send this mail to the right place.

I'm porting a new guest arch. It jumps of out of physical page
constantly. So many TBs cannot be chained with goto_tb. I'm wondering 
if the following check is still necessary?

	bool translator_use_goto_tb(DisasContextBase *db, target_ulong dest)
	{
	    /* Suppress goto_tb if requested. */
	    if (tb_cflags(db->tb) & CF_NO_GOTO_TB) {
		return false;
	    }

	    /* Check for the dest on the same page as the start of the TB.  */
	    return ((db->pc_first ^ dest) & TARGET_PAGE_MASK) == 0;    <--- Is this check really necessary?
	}

Now the chained TBs have been link with tb_link_page(), the chain will
be rebuilt if it is invalidate on page. So why is this check still there?

Acutally, I have tested some use cases with this check removed. It works
fine. Could anybody tell me in what case it is still necessary?

Thanks.


-- 
			-Kenneth


             reply	other threads:[~2023-02-15 15:19 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-15  8:39 Kenneth Lee [this message]
2023-02-15 17:27 ` Does the page boundary check still necessary? Richard Henderson
2023-02-16  1:45   ` Kenneth Lee
2023-02-16  2:26     ` Richard Henderson
2023-02-16  2:28       ` Kenneth Lee
2023-02-16  2:52         ` Richard Henderson
2023-02-16  9:35           ` Kenneth Lee

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