From: "Daniel P. Berrangé" <berrange@redhat.com>
To: Daniel Henrique Barboza <daniel.barboza@oss.qualcomm.com>
Cc: "Portia Stephens" <portias@oss.tenstorrent.com>,
qemu-devel@nongnu.org, "Nicholas Piggin" <npiggin@gmail.com>,
"Palmer Dabbelt" <palmer@dabbelt.com>,
"Chao Liu" <chao.liu@processmission.com>,
"Alistair Francis" <alistair.francis@wdc.com>,
qemu-riscv@nongnu.org,
"Philippe Mathieu-Daudé" <philmd@oss.qualcomm.com>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Joel Stanley" <joel@jms.id.au>,
"Liu Zhiwei" <zhiwei_liu@linux.alibaba.com>,
"Alex Bennée" <alex.bennee@linaro.org>,
"Pierrick Bouvier" <pierrick.bouvier@oss.qualcomm.com>,
"Weiwei Li" <liwei1518@gmail.com>,
"Anirudh Srinivasan" <asrinivasan@oss.tenstorrent.com>,
"Richard Henderson" <richard.henderson@linaro.org>,
"Zhao Liu" <zhao1.liu@intel.com>,
"Michael Ellerman" <mpe@kernel.org>
Subject: Re: [PATCH 07/12] machine: Support extra board CPUs outside -smp
Date: Fri, 16 Oct 2026 11:26:03 +0100 [thread overview]
Message-ID: <atH7u-UCZ3dbA-ui@redhat.com> (raw)
In-Reply-To: <b87a7231-ca35-4c1d-bc05-ffeee15eebf0@oss.qualcomm.com>
On Thu, Oct 15, 2026 at 05:31:33PM -0300, Daniel Henrique Barboza wrote:
> Phil, Pierrick,
>
> This patch seems to dwell around your turf. Did you think about how to
> instantiate different CPUs that might have different SMP topologies in
> the context of single binary/split accel work?
IMHO the -smp argument as it exists today is essentially unfixable
for the general case and will ultimately need to be declared legacy
/ for simplistic usage only. Trying to paper over the limitations of
-smp with special cases like "extra cpus" is unlikely to deliver
attractive solutions long term.
The eventual emulation of heterogeneous CPUS in the single binary
work will bring this to a head, but it already causes problems
today with our per-target binaries because even individual the real
world CPUs we want to be able to model are not symmetric.
As a historical reference, a while back, Zhao had an RFC that proposed
we use '-device' to define each topology level discretely, which would
allow for arbitrary asymmetric topologies:
https://lists.gnu.org/archive/html/qemu-devel/2024-09/msg03727.html
With regards,
Daniel
--
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next prev parent reply other threads:[~2026-10-16 10:26 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-15 3:17 [PATCH 00/12] Add the RCPU to Tenstorrent Atlantis Portia Stephens
2026-10-15 3:17 ` [PATCH 01/12] hw/riscv/atlantis: Set valid_cpu_types for Atlantis machine Portia Stephens
2026-10-15 3:17 ` [PATCH 02/12] hw/riscv/atlantis: Update fdt functions to take generic parameters Portia Stephens
2026-10-15 3:17 ` [PATCH 03/12] hw/riscv/atlantis: Move Ascalon into cluster struct Portia Stephens
2026-10-15 3:17 ` [PATCH 04/12] hw/riscv/atlantis: Store Ascalon memory in " Portia Stephens
2026-10-15 3:17 ` [PATCH 05/12] hw/riscv/atlantis: Create CPU cluster for Atlantis cpus Portia Stephens
2026-10-15 3:17 ` [PATCH 06/12] target/riscv: Add Tenstorrent Real-time CPU Portia Stephens
2026-10-15 3:17 ` [PATCH 07/12] machine: Support extra board CPUs outside -smp Portia Stephens
2026-10-15 20:31 ` Daniel Henrique Barboza
2026-10-16 10:26 ` Daniel P. Berrangé [this message]
2026-10-16 11:23 ` Daniel Henrique Barboza
2026-10-15 3:18 ` [PATCH 08/12] hw/riscv/atlantis: Add the RCPU to the Atlantis SoC Portia Stephens
2026-10-15 3:18 ` [PATCH 09/12] hw/riscv/atlantis: Back RCPU memory region by unimplemented device Portia Stephens
2026-10-15 3:18 ` [PATCH 10/12] hw/riscv/atlantis: Load the RCPU bootrom Portia Stephens
2026-10-15 3:18 ` [PATCH 11/12] tests/functional/riscv64: Add rcpu to tt-atlantis tests Portia Stephens
2026-10-15 3:18 ` [PATCH 12/12] docs/atlantis: Update Atlantis documentation to include the RCPU Portia Stephens
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