From: "Daniel P. Berrangé" <berrange@redhat.com>
To: Yanan Wang <wangyanan55@huawei.com>
Cc: Peter Maydell <peter.maydell@linaro.org>,
Andrew Jones <drjones@redhat.com>,
Eduardo Habkost <ehabkost@redhat.com>,
"Michael S . Tsirkin" <mst@redhat.com>,
wanghaibin.wang@huawei.com,
Richard Henderson <richard.henderson@linaro.org>,
qemu-devel@nongnu.org, Greg Kurz <groug@kaod.org>,
Halil Pasic <pasic@linux.ibm.com>,
yuzenghui@huawei.com, Igor Mammedov <imammedo@redhat.com>,
Thomas Huth <thuth@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>,
David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [PATCH for-6.2 v2 01/11] machine: Disallow specifying topology parameters as zero
Date: Mon, 19 Jul 2021 17:46:06 +0100 [thread overview]
Message-ID: <YPWsThPiZa3mF+zp@redhat.com> (raw)
In-Reply-To: <20210719032043.25416-2-wangyanan55@huawei.com>
On Mon, Jul 19, 2021 at 11:20:33AM +0800, Yanan Wang wrote:
> In the SMP configuration, we should either specify a topology
> parameter with a reasonable value (equal to or greater than 1)
> or just leave it omitted and QEMU will calculate its value.
>
> Configurations which explicitly specify the topology parameters
> as zero like "sockets=0" are meaningless, so disallow them.
>
> Suggested-by: Andrew Jones <drjones@redhat.com>
> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> ---
> hw/core/machine.c | 31 +++++++++++++++++++++++--------
> hw/i386/pc.c | 29 +++++++++++++++++++++--------
> qapi/machine.json | 4 ++--
> 3 files changed, 46 insertions(+), 18 deletions(-)
>
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 775add0795..d73daa10f4 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -745,11 +745,25 @@ static void smp_parse(MachineState *ms, SMPConfiguration *config, Error **errp)
> {
> unsigned cpus = config->has_cpus ? config->cpus : 0;
> unsigned sockets = config->has_sockets ? config->sockets : 0;
> + unsigned dies = config->has_dies ? config->dies : 1;
It looks odd to set dies=1 by default at initially, when everything
else is set to 0. I realize you're just copying existing pc_smp_parse
code in this respect, but I feel like could benefit from a separate
initialization with a comment to explain why we're hardcoding it
to 1....
> unsigned cores = config->has_cores ? config->cores : 0;
> unsigned threads = config->has_threads ? config->threads : 0;
> + unsigned maxcpus = config->has_maxcpus ? config->maxcpus : 0;
> +
> + if ((config->has_cpus && config->cpus == 0) ||
> + (config->has_sockets && config->sockets == 0) ||
> + (config->has_dies && config->dies == 0) ||
> + (config->has_cores && config->cores == 0) ||
> + (config->has_threads && config->threads == 0) ||
> + (config->has_maxcpus && config->maxcpus == 0)) {
> + error_setg(errp, "parameters must be equal to or greater than one"
> + "if provided");
> + return;
> + }
>
> - if (config->has_dies && config->dies != 0 && config->dies != 1) {
> + if (dies > 1) {
> error_setg(errp, "dies not supported by this machine's CPU topology");
> + return;
> }
.... eg how about here adding
/* Never try to assign multiple dies when defaulting omitted topology */
if (dies == 0) {
dies = 1;
}
> diff --git a/qapi/machine.json b/qapi/machine.json
> index c3210ee1fb..c11b2e6f73 100644
> --- a/qapi/machine.json
> +++ b/qapi/machine.json
> @@ -1288,8 +1288,8 @@
> ##
> # @SMPConfiguration:
> #
> -# Schema for CPU topology configuration. "0" or a missing value lets
> -# QEMU figure out a suitable value based on the ones that are provided.
> +# Schema for CPU topology configuration. A missing value lets QEMU
> +# figure out a suitable value based on the ones that are provided.
Hmm, so we had actually documented that '0' had the same semantics
as omitting a parameter. This was done in:
commit 1e63fe685804dfadddd643bf3860b1a59702d4bf
Author: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu Jun 17 17:53:06 2021 +0200
machine: pass QAPI struct to mc->smp_parse
which hasn't been released yet.
This was possible, but never documented, with the traditiaonl -smp
impl before it was qapi-ified. I think that historical behaviour
was simply a side effect of the QemuOpts impl rather than an
intentional design, hence not documented.
At the very least I think need to get rid of this bit of docs about
"0" before this release, otherwise we'll have stronger need to
consider a real deprecation process.
Regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
next prev parent reply other threads:[~2021-07-19 16:47 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-19 3:20 [PATCH for-6.2 v2 00/11] machine: smp parsing fixes and improvement Yanan Wang
2021-07-19 3:20 ` [PATCH for-6.2 v2 01/11] machine: Disallow specifying topology parameters as zero Yanan Wang
2021-07-19 16:11 ` Andrew Jones
2021-07-21 12:34 ` wangyanan (Y)
2021-07-19 16:46 ` Daniel P. Berrangé [this message]
2021-07-21 12:35 ` wangyanan (Y)
2021-07-19 3:20 ` [PATCH for-6.2 v2 02/11] machine: Make smp_parse generic enough for all arches Yanan Wang
2021-07-19 16:28 ` Andrew Jones
2021-07-19 16:36 ` Daniel P. Berrangé
2021-07-19 16:48 ` Andrew Jones
2021-07-19 16:50 ` Daniel P. Berrangé
2021-07-19 16:53 ` Daniel P. Berrangé
2021-07-22 7:18 ` wangyanan (Y)
2021-07-20 6:57 ` Cornelia Huck
2021-07-22 7:12 ` wangyanan (Y)
2021-07-19 3:20 ` [PATCH for-6.2 v2 03/11] machine: Uniformly use maxcpus to calculate the omitted parameters Yanan Wang
2021-07-19 16:36 ` Andrew Jones
2021-07-22 3:00 ` wangyanan (Y)
2021-07-19 3:20 ` [PATCH for-6.2 v2 04/11] machine: Use the computed parameters to calculate omitted cpus Yanan Wang
2021-07-19 16:42 ` Andrew Jones
2021-07-22 4:42 ` wangyanan (Y)
2021-07-22 12:27 ` Andrew Jones
2021-07-22 14:59 ` wangyanan (Y)
2021-07-22 15:05 ` Andrew Jones
2021-07-22 15:45 ` wangyanan (Y)
2021-07-19 3:20 ` [PATCH for-6.2 v2 05/11] machine: Improve the error reporting of smp parsing Yanan Wang
2021-07-19 16:53 ` Andrew Jones
2021-07-22 8:10 ` wangyanan (Y)
2021-07-22 12:47 ` Andrew Jones
2021-07-19 3:20 ` [PATCH for-6.2 v2 06/11] hw: Add compat machines for 6.2 Yanan Wang
2021-07-19 3:38 ` David Gibson
2021-07-19 17:00 ` Andrew Jones
2021-07-19 17:03 ` Cornelia Huck
2021-07-19 23:45 ` Pankaj Gupta
2021-07-19 3:20 ` [PATCH for-6.2 v2 07/11] machine: Prefer cores over sockets in smp parsing since 6.2 Yanan Wang
2021-07-19 3:40 ` David Gibson
2021-07-22 5:22 ` wangyanan (Y)
2021-07-19 17:13 ` Andrew Jones
2021-07-22 5:32 ` wangyanan (Y)
2021-07-19 3:20 ` [PATCH for-6.2 v2 08/11] machine: Use ms instead of global current_machine in sanity-check Yanan Wang
2021-07-19 17:14 ` Andrew Jones
2021-07-19 3:20 ` [PATCH for-6.2 v2 09/11] machine: Tweak the order of topology members in struct CpuTopology Yanan Wang
2021-07-19 3:20 ` [PATCH for-6.2 v2 10/11] machine: Split out the smp parsing code Yanan Wang
2021-07-19 17:20 ` Andrew Jones
2021-07-22 6:24 ` wangyanan (Y)
2021-07-22 13:07 ` Andrew Jones
2021-07-22 14:29 ` wangyanan (Y)
2021-07-19 3:20 ` [PATCH for-6.2 v2 11/11] tests/unit: Add a unit test for smp parsing Yanan Wang
2021-07-19 18:57 ` Andrew Jones
2021-07-22 6:15 ` wangyanan (Y)
2021-07-22 13:12 ` Andrew Jones
2021-07-22 14:18 ` wangyanan (Y)
2021-07-19 16:57 ` [PATCH for-6.2 v2 00/11] machine: smp parsing fixes and improvement Cornelia Huck
2021-07-21 12:38 ` wangyanan (Y)
2021-07-21 13:52 ` Pankaj Gupta
2021-07-22 2:22 ` wangyanan (Y)
2021-07-22 7:51 ` Pierre Morel
2021-07-22 8:32 ` wangyanan (Y)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=YPWsThPiZa3mF+zp@redhat.com \
--to=berrange@redhat.com \
--cc=david@gibson.dropbear.id.au \
--cc=drjones@redhat.com \
--cc=ehabkost@redhat.com \
--cc=groug@kaod.org \
--cc=imammedo@redhat.com \
--cc=mst@redhat.com \
--cc=pasic@linux.ibm.com \
--cc=pbonzini@redhat.com \
--cc=peter.maydell@linaro.org \
--cc=qemu-devel@nongnu.org \
--cc=richard.henderson@linaro.org \
--cc=thuth@redhat.com \
--cc=wanghaibin.wang@huawei.com \
--cc=wangyanan55@huawei.com \
--cc=yuzenghui@huawei.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).