Re: [Xen-devel] [PATCH v3 1/7] x86: detect and initialize Cache QoS Monitoring feature

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 29/11/13 05:48, dongxiao.xu@xxxxxxxxx wrote:
> From: Dongxiao Xu <dongxiao.xu@xxxxxxxxx>
>
> Detect platform QoS feature status and enumerate the resource types,
> one of which is to monitor the L3 cache occupancy.
>
> Also introduce a Xen grub command line parameter to control the
> QoS feature status globally.
>
> Signed-off-by: Jiongxi Li <jiongxi.li@xxxxxxxxx>
> Signed-off-by: Dongxiao Xu <dongxiao.xu@xxxxxxxxx>

This is starting to look good.  Sorry to keep nitpicking at it.

> ---
>  xen/arch/x86/Makefile            |    1 +
>  xen/arch/x86/cpu/intel.c         |    6 +++
>  xen/arch/x86/pqos.c              |   95 
> ++++++++++++++++++++++++++++++++++++++
>  xen/arch/x86/setup.c             |    3 ++
>  xen/include/asm-x86/cpufeature.h |    1 +
>  xen/include/asm-x86/pqos.h       |   32 +++++++++++++
>  6 files changed, 138 insertions(+)
>  create mode 100644 xen/arch/x86/pqos.c
>  create mode 100644 xen/include/asm-x86/pqos.h
>
> diff --git a/xen/arch/x86/Makefile b/xen/arch/x86/Makefile
> index d502bdf..54962e0 100644
> --- a/xen/arch/x86/Makefile
> +++ b/xen/arch/x86/Makefile
> @@ -58,6 +58,7 @@ obj-y += crash.o
>  obj-y += tboot.o
>  obj-y += hpet.o
>  obj-y += xstate.o
> +obj-y += pqos.o
>  
>  obj-$(crash_debug) += gdbstub.o
>  
> diff --git a/xen/arch/x86/cpu/intel.c b/xen/arch/x86/cpu/intel.c
> index 27fe762..f0d83ea 100644
> --- a/xen/arch/x86/cpu/intel.c
> +++ b/xen/arch/x86/cpu/intel.c
> @@ -230,6 +230,12 @@ static void __devinit init_intel(struct cpuinfo_x86 *c)
>            ( c->cpuid_level >= 0x00000006 ) &&
>            ( cpuid_eax(0x00000006) & (1u<<2) ) )
>               set_bit(X86_FEATURE_ARAT, c->x86_capability);
> +
> +     /* Check platform QoS monitoring capability */
> +     if ((c->cpuid_level >= 0x00000007) &&
> +         (cpuid_ebx(0x00000007) & (1u<<12)))
> +             set_bit(X86_FEATURE_QOSM, c->x86_capability);
> +
>  }
>  
>  static struct cpu_dev intel_cpu_dev __cpuinitdata = {
> diff --git a/xen/arch/x86/pqos.c b/xen/arch/x86/pqos.c
> new file mode 100644
> index 0000000..e2172c4
> --- /dev/null
> +++ b/xen/arch/x86/pqos.c
> @@ -0,0 +1,95 @@
> +/*
> + * pqos.c: Platform QoS related service for guest.
> + *
> + * Copyright (c) 2013, Intel Corporation
> + * Author: Jiongxi Li  <jiongxi.li@xxxxxxxxx>
> + * Author: Dongxiao Xu <dongxiao.xu@xxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along 
> with
> + * this program; if not, write to the Free Software Foundation, Inc., 59 
> Temple
> + * Place - Suite 330, Boston, MA 02111-1307 USA.
> + */
> +#include <asm/processor.h>
> +#include <xen/init.h>
> +#include <asm/pqos.h>
> +
> +static bool_t __initdata pqos_enabled = 1;
> +boolean_param("pqos", pqos_enabled);
> +
> +static unsigned int cqm_rmid_count = 256;

This can probably be __read_mostly.  Also, I would suggest
"opt_max_rmids" as a name which makes it obvious when used elsewhere
that it is a command line parameter limiting the possible rmids.

> +integer_param("cqm_rmid_count", cqm_rmid_count);

Any patch adding new command line parameters should also patch
docs/misc/xen-command-line.markdown, to help keep the documentation up
to date.

However, I feel that all options relating to platform QoS should be
available under a "qpos" custom_param, (similar to iommu=), so we don't
end up with loads of new command line options with common prefixes as
new features are added.

For this, I would suggest semantic like:

pqos=[<boolean>],[max_rmids=<number>]

Particularly, when a second qpos option is introduced, it might be
sensible to have individual booleans for each option, as well as a
global enable/disable.


I would be interested in general views from others as far as this is
concerned.

~Andrew

> +
> +unsigned int cqm_upscaling_factor = 0;
> +bool_t cqm_enabled = 0;
> +domid_t *cqm_rmid_array = NULL;
> +
> +static void __init init_cqm(void)
> +{
> +    unsigned int rmid;
> +    unsigned int eax, edx;
> +    unsigned int max_cqm_rmid;
> +
> +    cpuid_count(0xf, 1, &eax, &cqm_upscaling_factor, &max_cqm_rmid, &edx);
> +    if ( !(edx & QOS_MONITOR_EVTID_L3) )
> +        return;
> +
> +    cqm_rmid_count = min(cqm_rmid_count, max_cqm_rmid + 1);
> +
> +    cqm_rmid_array = xzalloc_array(domid_t, cqm_rmid_count);

You fully populate the contents of the array lower.  No need to waste
time zeroing it first.

> +    if ( !cqm_rmid_array )
> +    {
> +        cqm_rmid_count = 0;
> +        return;
> +    }
> +
> +    /* Reserve RMID 0 for all domains not being monitored */
> +    cqm_rmid_array[0] = DOMID_XEN;
> +
> +    for ( rmid = 1; rmid < cqm_rmid_count; rmid++ )
> +        cqm_rmid_array[rmid] = DOMID_INVALID;
> +
> +    cqm_enabled = 1;
> +
> +    printk(XENLOG_INFO "Cache QoS Monitoring Enabled.\n");
> +}
> +
> +static void __init init_qos_monitor(void)
> +{
> +    unsigned int qm_features;
> +    unsigned int eax, ebx, ecx;
> +
> +    if ( !(boot_cpu_has(X86_FEATURE_QOSM)) )
> +        return;
> +
> +    cpuid_count(0xf, 0, &eax, &ebx, &ecx, &qm_features);
> +
> +    if ( qm_features & QOS_MONITOR_TYPE_L3 )
> +        init_cqm();
> +}
> +
> +void __init init_platform_qos(void)
> +{
> +    if ( !pqos_enabled )
> +        return;
> +
> +    init_qos_monitor();
> +}
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * tab-width: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
> index 5bf4ee0..95418e4 100644
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -48,6 +48,7 @@
>  #include <asm/setup.h>
>  #include <xen/cpu.h>
>  #include <asm/nmi.h>
> +#include <asm/pqos.h>
>  
>  /* opt_nosmp: If true, secondary processors are ignored. */
>  static bool_t __initdata opt_nosmp;
> @@ -1402,6 +1403,8 @@ void __init __start_xen(unsigned long mbi_p)
>  
>      domain_unpause_by_systemcontroller(dom0);
>  
> +    init_platform_qos();
> +
>      reset_stack_and_jump(init_done);
>  }
>  
> diff --git a/xen/include/asm-x86/cpufeature.h 
> b/xen/include/asm-x86/cpufeature.h
> index 1cfaf94..ca59668 100644
> --- a/xen/include/asm-x86/cpufeature.h
> +++ b/xen/include/asm-x86/cpufeature.h
> @@ -147,6 +147,7 @@
>  #define X86_FEATURE_ERMS     (7*32+ 9) /* Enhanced REP MOVSB/STOSB */
>  #define X86_FEATURE_INVPCID  (7*32+10) /* Invalidate Process Context ID */
>  #define X86_FEATURE_RTM      (7*32+11) /* Restricted Transactional Memory */
> +#define X86_FEATURE_QOSM     (7*32+12) /* Platform QoS monitoring capability 
> */
>  #define X86_FEATURE_NO_FPU_SEL       (7*32+13) /* FPU CS/DS stored as zero */
>  #define X86_FEATURE_SMAP     (7*32+20) /* Supervisor Mode Access Prevention 
> */
>  
> diff --git a/xen/include/asm-x86/pqos.h b/xen/include/asm-x86/pqos.h
> new file mode 100644
> index 0000000..e8caca2
> --- /dev/null
> +++ b/xen/include/asm-x86/pqos.h
> @@ -0,0 +1,32 @@
> +/*
> + * pqos.h: Platform QoS related service for guest.
> + *
> + * Copyright (c) 2013, Intel Corporation
> + * Author: Jiongxi Li  <jiongxi.li@xxxxxxxxx>
> + * Author: Dongxiao Xu <dongxiao.xu@xxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along 
> with
> + * this program; if not, write to the Free Software Foundation, Inc., 59 
> Temple
> + * Place - Suite 330, Boston, MA 02111-1307 USA.
> + */
> +#ifndef ASM_PQOS_H
> +#define ASM_PQOS_H
> +
> +/* QoS Resource Type Enumeration */
> +#define QOS_MONITOR_TYPE_L3            0x2
> +
> +/* QoS Monitoring Event ID */
> +#define QOS_MONITOR_EVTID_L3           0x1
> +
> +void init_platform_qos(void);
> +
> +#endif


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