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From: Richard Henderson <>
To: Bruno Piazera Larsen <>,
	Greg Kurz <>,,,,,
Subject: Re: [RFC PATCH] target/ppc: fix address translation bug for hash table mmus
Date: Tue, 8 Jun 2021 08:35:03 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 6/8/21 7:39 AM, Bruno Piazera Larsen wrote:
>> That's odd.  We already have more arguments than the number of argument 
>> registers...  A 5x slowdown is distinctly odd.
> I did some more digging and the problem is not with ppc_radix64_check_prot, the 
> problem is ppc_radix64_xlate, which currently has 7 arguments and we're 
> increasing to 8. 7 feels like the correct number, but I couldn't find docs 
> supporting it, so I could be wrong.

According to tcg/ppc/, there are 8 argument registers for ppc 
hosts.  But now I see you didn't actually say on which host you observed the 
problem...  It's 6 argument registers for x86_64 host.

> That means we'd have to define radix_ctx_t (or however we call it) in 
> radix64.h, setup the struct on ppc_xlate, then pass it to ppc_radix64_xlate.

Well, if you're going to change the xlate interface, you want to do that across 
all of them.  So, not call it radix_ctx_t.

>  From looking at the code, it seems the most useful bits to put in the struct 
> are: eaddr, g_addr, h_addr, {h,g}_prot, {g,h}_page_size, mmu_idx and 
> guest_visible. They all seem reasonable to me, but I might be missing something 
> again.

I don't think h/g should be in this struct.  I think h/g should use different 
struct instances, because they are different accesses.


  reply	other threads:[~2021-06-08 15:36 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-02 19:18 Bruno Larsen (billionai)
2021-06-02 19:26 ` Richard Henderson
2021-06-02 19:58   ` Bruno Piazera Larsen
2021-06-02 22:19     ` Richard Henderson
2021-06-07 19:29       ` Bruno Piazera Larsen
2021-06-07 21:06         ` Richard Henderson
2021-06-08 14:39           ` Bruno Piazera Larsen
2021-06-08 15:35             ` Richard Henderson [this message]
2021-06-08 16:37               ` Bruno Piazera Larsen
2021-06-08 18:39                 ` Bruno Piazera Larsen

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