Re: [PATCH v10 11/14] machine: Make smp_parse generic enough for all arches

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>,
	Cornelia Huck <cohuck@redhat.com>,
	Eduardo Habkost <ehabkost@redhat.com>,
	Pierre Morel <pmorel@linux.ibm.com>,
	"Michael S . Tsirkin" <mst@redhat.com>,
	Pankaj Gupta <pankaj.gupta.linux@gmail.com>,
	qemu-devel@nongnu.org, qemu-s390x@nongnu.org,
	qemu-arm@nongnu.org, qemu-ppc@nongnu.org,
	wanghaibin.wang@huawei.com, Paolo Bonzini <pbonzini@redhat.com>,
	David Gibson <david@gibson.dropbear.id.au>
Subject: Re: [PATCH v10 11/14] machine: Make smp_parse generic enough for all arches
Date: Mon, 27 Sep 2021 11:12:35 +0100	[thread overview]
Message-ID: <YVGZE7boLhoD1w2r@redhat.com> (raw)
In-Reply-To: <20210926084541.17352-12-wangyanan55@huawei.com>

On Sun, Sep 26, 2021 at 04:45:38PM +0800, Yanan Wang wrote:
> Currently the only difference between smp_parse and pc_smp_parse
> is the support of dies parameter and the related error reporting.
> With some arch compat variables like "bool dies_supported", we can
> make smp_parse generic enough for all arches and the PC specific
> one can be removed.
> 
> Making smp_parse() generic enough can reduce code duplication and
> ease the code maintenance, and also allows extending the topology
> with more arch specific members (e.g., clusters) in the future.
> 
> Suggested-by: Andrew Jones <drjones@redhat.com>
> Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
> Reviewed-by: Andrew Jones <drjones@redhat.com>
> ---
>  hw/core/machine.c   | 110 ++++++++++++++++++++++++++++++++++++--------
>  hw/i386/pc.c        |  84 +--------------------------------
>  include/hw/boards.h |   9 ++++
>  3 files changed, 100 insertions(+), 103 deletions(-)
> 
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index a21fcd7700..4b5c943f8e 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -15,6 +15,7 @@
>  #include "qapi/qmp/qerror.h"
>  #include "sysemu/replay.h"
>  #include "qemu/units.h"
> +#include "qemu/cutils.h"
>  #include "hw/boards.h"
>  #include "hw/loader.h"
>  #include "qapi/error.h"
> @@ -746,20 +747,87 @@ void machine_set_cpu_numa_node(MachineState *machine,
>      }
>  }
>  
> +static char *cpu_topology_hierarchy(MachineState *ms)
> +{
> +    MachineClass *mc = MACHINE_GET_CLASS(ms);
> +    SMPCompatProps *smp_props = &mc->smp_props;
> +    char topo_msg[256] = "";
> +
> +    /*
> +     * Topology members should be ordered from the largest to the smallest.
> +     * Concept of sockets/cores/threads is supported by default and will be
> +     * reported in the hierarchy. Unsupported members will not be reported.
> +     */
> +    g_autofree char *sockets_msg = g_strdup_printf(
> +            " * sockets (%u)", ms->smp.sockets);
> +    pstrcat(topo_msg, sizeof(topo_msg), sockets_msg);
> +
> +    if (smp_props->dies_supported) {
> +        g_autofree char *dies_msg = g_strdup_printf(
> +                " * dies (%u)", ms->smp.dies);
> +        pstrcat(topo_msg, sizeof(topo_msg), dies_msg);
> +    }
> +
> +    g_autofree char *cores_msg = g_strdup_printf(
> +            " * cores (%u)", ms->smp.cores);
> +    pstrcat(topo_msg, sizeof(topo_msg), cores_msg);
> +
> +    g_autofree char *threads_msg = g_strdup_printf(
> +            " * threads (%u)", ms->smp.threads);
> +    pstrcat(topo_msg, sizeof(topo_msg), threads_msg);
> +
> +    return g_strdup_printf("%s", topo_msg + 3);
> +}

Mixing g_strdup_printf + pstrcat + fixed buffer is quite
unpleasant. This method is begging to use 'GString' APIs
for formatting.

Regards,
Daniel
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