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Re: [Qemu-devel] [PATCH v12 2/4] i386: Verify if topoext feature can be
From: |
Moger, Babu |
Subject: |
Re: [Qemu-devel] [PATCH v12 2/4] i386: Verify if topoext feature can be supported |
Date: |
Thu, 7 Jun 2018 14:24:18 +0000 |
> -----Original Message-----
> From: Eduardo Habkost [mailto:address@hidden
> Sent: Wednesday, June 6, 2018 5:06 PM
> To: Moger, Babu <address@hidden>
> Cc: address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden; address@hidden
> Subject: Re: [PATCH v12 2/4] i386: Verify if topoext feature can be supported
>
> On Wed, Jun 06, 2018 at 10:36:44AM -0400, Babu Moger wrote:
> > topoext feature cannot be supported in certain cases
> > with large number of cores or threads. Add the check.
> >
> > Signed-off-by: Babu Moger <address@hidden>
> > ---
> > target/i386/cpu.c | 27 +++++++++++++++++++++++++++
> > 1 file changed, 27 insertions(+)
> >
> > diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> > index 86fb1a4..fc5c66d 100644
> > --- a/target/i386/cpu.c
> > +++ b/target/i386/cpu.c
> > @@ -509,6 +509,20 @@ static void encode_topo_cpuid8000001e(CPUState
> *cs, X86CPU *cpu,
> > }
> >
> > /*
> > + * Check if we can support this topology
> > + * Fail if number of cores are beyond the supported config
> > + * or nr_threads is more than 2
> > + */
> > +static int topology_supports_topoext(int nr_cores, int nr_threads)
> > +{
> > + if ((nr_cores > (MAX_CORES_IN_NODE * MAX_NODES_PER_SOCKET))
> ||
> > + (nr_threads > 2)) {
> > + return 0;
> > + }
> > + return 1;
> > +}
> > +
> > +/*
> > * Definitions of the hardcoded cache entries we expose:
> > * These are legacy cache values. If there is a need to change any
> > * of these values please use builtin_x86_defs
> > @@ -4941,6 +4955,19 @@ static void x86_cpu_realizefn(DeviceState *dev,
> Error **errp)
> >
> > qemu_init_vcpu(cs);
> >
> > + /* On AMD systems, check if we can support topoext feature */
> > + if (IS_AMD_CPU(env) &&
> > + (env->features[FEAT_8000_0001_ECX] & CPUID_EXT3_TOPOEXT)) {
> > + if (!topology_supports_topoext(cs->nr_cores, cs->nr_threads)) {
> > + /* Cannot support topoext */
> > + error_setg(errp, "CPU model does not support topoext
> > feature "
> > + "with number of cores(%d) and
> > threads(%d). "
> > + "Please configure -smp options properly.",
> > + cs->nr_cores, cs->nr_threads);
>
> See error.h documentation:
>
> * Error reporting system loosely patterned after Glib's GError.
> *
> * Create an error:
> * error_setg(&err, "situation normal, all fouled up");
> *
> * Create an error and add additional explanation:
> * error_setg(&err, "invalid quark");
> * error_append_hint(&err, "Valid quarks are up, down, strange, "
> * "charm, top, bottom.\n");
> *
> * Do *not* contract this to
> * error_setg(&err, "invalid quark\n"
> * "Valid quarks are up, down, strange, charm, top, bottom.");
> *
>
> I suggest something like this:
Sure. I will make these changes. Thanks
>
> static bool topology_supports_topoext(int nr_cores, int nr_threads, Error
> **errp)
> {
> if (nr_cores > (MAX_CORES_IN_NODE * MAX_NODES_PER_SOCKET))) {
> error_setg(errp, "TOPOEXT unsupported with %d cores per socket",
> nr_cores);
> error_append_hint(errp, "TOPOEXT supports only up to %d cores per
> socket",
> (MAX_CORES_IN_NODE * MAX_NODES_PER_SOCKET));
> return false;
> }
> if (nr_threads > 2) {
> error_setg(errp, "TOPOEXT unsupported with %d threads per core",
> nr_threads);
> error_append_hint(errp, "TOPOEXT supports only up to 2 threads per
> core");
> (MAX_CORES_IN_NODE * MAX_NODES_PER_SOCKET));
> return false;
> }
> return true;
> }
>
> static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
> {
> /* ... */
> if (IS_AMD_CPU(env) &&
> (env->features[FEAT_8000_0001_ECX] & CPUID_EXT3_TOPOEXT) &&
> !topology_supports_topoext(cs->nr_cores, cs->nr_threads, errp)) {
> return;
> }
> /* ... */
> }
>
> --
> Eduardo
- [Qemu-devel] [PATCH v12 0/4] i386: Enable TOPOEXT to support hyperthreading on AMD CPU, Babu Moger, 2018/06/06
- [Qemu-devel] [PATCH v12 3/4] i386: Enable TOPOEXT feature on AMD EPYC CPU, Babu Moger, 2018/06/06
- Re: [Qemu-devel] [PATCH v12 3/4] i386: Enable TOPOEXT feature on AMD EPYC CPU, Eduardo Habkost, 2018/06/06
- Re: [Qemu-devel] [PATCH v12 3/4] i386: Enable TOPOEXT feature on AMD EPYC CPU, Moger, Babu, 2018/06/08
- Re: [Qemu-devel] [PATCH v12 3/4] i386: Enable TOPOEXT feature on AMD EPYC CPU, Eduardo Habkost, 2018/06/08
- Re: [Qemu-devel] [PATCH v12 3/4] i386: Enable TOPOEXT feature on AMD EPYC CPU, Moger, Babu, 2018/06/08
- Re: [Qemu-devel] [PATCH v12 3/4] i386: Enable TOPOEXT feature on AMD EPYC CPU, Eduardo Habkost, 2018/06/08
- Re: [Qemu-devel] [PATCH v12 3/4] i386: Enable TOPOEXT feature on AMD EPYC CPU, Moger, Babu, 2018/06/08
- Re: [Qemu-devel] [PATCH v12 3/4] i386: Enable TOPOEXT feature on AMD EPYC CPU, Moger, Babu, 2018/06/08
[Qemu-devel] [PATCH v12 4/4] i386: Remove generic SMT thread check, Babu Moger, 2018/06/06