From: Richard Henderson <richard.henderson@linaro.org>
To: Nicholas Piggin <npiggin@gmail.com>, qemu-ppc@nongnu.org
Cc: qemu-devel@nongnu.org
Subject: Re: [RFC PATCH 0/3] translation performance improvements
Date: Mon, 31 Mar 2025 14:40:04 -0500 [thread overview]
Message-ID: <6e647368-9fde-4c7f-ac17-d4c4e46fab3a@linaro.org> (raw)
In-Reply-To: <20250331155423.619451-1-npiggin@gmail.com>
On 3/31/25 10:54, Nicholas Piggin wrote:
> I've been struggling with these couple of performance issues with
> TB coherency. I almost thought deferring flush to icbi would be
> workable, buta note in the docs says that exceptions require TB
> to be coherent... I don't know what requires that, maybe it could
> be worked around?
Which note? Anyway, qemu implements accurate tb invalidation for x86 and s390x, which
means we don't really need to do anything special for other targets.
Compare aarch64 "IC_IVAU" which (at least for system mode) is implemented as a nop.
> Another thing is PowerVM runtime firmware runs with MMU disabled
> for ifetch. This means a fixed linear map with no memory protection.
> Is it possible we can enable goto tb across TARGET_PAGE_SIZE for
> ifetches in this mode?
No, there are several things that assume nothing jumps across TARGET_PAGE_SIZE, including
breakpoints.
r~
next prev parent reply other threads:[~2025-03-31 19:40 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-03-31 15:54 [RFC PATCH 0/3] translation performance improvements Nicholas Piggin
2025-03-31 15:54 ` [RFC PATCH 1/3] accel/tcg: Option to permit incoherent translation block cache vs stores Nicholas Piggin
2025-03-31 19:51 ` Richard Henderson
2025-04-01 8:34 ` Nicholas Piggin
2025-04-01 8:42 ` Philippe Mathieu-Daudé
2025-03-31 15:54 ` [RFC PATCH 2/3] target/ppc: define TARGET_HAS_LAZY_ICACHE Nicholas Piggin
2025-03-31 15:54 ` [RFC PATCH 3/3] target/ppc: Allow goto-tb on fixed real mode translations Nicholas Piggin
2025-03-31 19:40 ` Richard Henderson [this message]
2025-04-01 8:33 ` [RFC PATCH 0/3] translation performance improvements Nicholas Piggin
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