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Re: [RFC PATCH 5/6] pc/machine: Disallow any configuration of dies for n


From: wangyanan (Y)
Subject: Re: [RFC PATCH 5/6] pc/machine: Disallow any configuration of dies for non-PC machines
Date: Mon, 5 Jul 2021 17:03:53 +0800
User-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0

On 2021/7/2 18:18, Daniel P. Berrangé wrote:
On Fri, Jul 02, 2021 at 06:07:38PM +0800, Yanan Wang wrote:
Since a machine type does not support topology parameter of dies,
it's probably more reasonable to reject any explicit specification
to avoid possible confuse, including "dies=0" and "dies=1" although
they won't affect the calculation of non-PC machines.

Also a comment of struct SMPConfiguration is fixed.

Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
---
  hw/core/machine.c | 2 +-
  qapi/machine.json | 2 +-
  2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 58882835be..55785feee2 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -747,7 +747,7 @@ static void smp_parse(MachineState *ms, SMPConfiguration 
*config, Error **errp)
      unsigned threads = config->has_threads ? config->threads : 0;
      unsigned maxcpus = config->has_maxcpus ? config->maxcpus : 0;
- if (config->has_dies && config->dies != 0 && config->dies != 1) {
+    if (config->has_dies) {
          error_setg(errp, "dies not supported by this machine's CPU topology");
      }
This will cause a functional regression. Libvirt always specifies
dies=1 if QEMU supports it.  I don't see a need to reject it,
since conceptually it is reasonable to say that all existing
CPUs have a single die. It simply that 99% of CPUs don't support
more than 1 die.
Ok, I agree. This is a sincere suggestion, but clearly i didn't consider
how Libvirt deals with configuration of dies. I will drop this part and
the single comment fix can be merged into patch #6.
diff --git a/qapi/machine.json b/qapi/machine.json
index c3210ee1fb..253f84abf6 100644
--- a/qapi/machine.json
+++ b/qapi/machine.json
@@ -1297,7 +1297,7 @@
  #
  # @dies: number of dies per socket in the CPU topology
  #
-# @cores: number of cores per thread in the CPU topology
+# @cores: number of cores per die in the CPU topology
  #
  # @threads: number of threads per core in the CPU topology
  #
This is a simple docs fix and ok

Thanks,
Yanan
.




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