Re: [PATCH v2 2/8] x86: handle CQM resource when creating/destroying guests

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 21/11/13 07:20, dongxiao.xu@intel.com wrote:
> From: Dongxiao Xu <dongxiao.xu@intel.com>
>
> Allocate an RMID for a guest when it is created. This per-guest
> RMID will be used to monitor Cache QoS related data. The RMID will
> be relinquished when guest is destroyed.
>
> Signed-off-by: Jiongxi Li <jiongxi.li@intel.com>
> Signed-off-by: Dongxiao Xu <dongxiao.xu@intel.com>
> ---
>  xen/arch/x86/domain.c        |    9 +++++++
>  xen/arch/x86/pqos.c          |   59 ++++++++++++++++++++++++++++++++++++++++++
>  xen/common/domctl.c          |    5 +++-
>  xen/include/asm-x86/domain.h |    2 ++
>  xen/include/asm-x86/pqos.h   |    4 +++
>  xen/include/public/domctl.h  |    3 +++
>  xen/include/xen/sched.h      |    3 +++
>  7 files changed, 84 insertions(+), 1 deletion(-)
>
> diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> index a3868f9..9725649 100644
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -60,6 +60,7 @@
>  #include <xen/numa.h>
>  #include <xen/iommu.h>
>  #include <compat/vcpu.h>
> +#include <asm/pqos.h>
>  
>  DEFINE_PER_CPU(struct vcpu *, curr_vcpu);
>  DEFINE_PER_CPU(unsigned long, cr4);
> @@ -579,6 +580,11 @@ int arch_domain_create(struct domain *d, unsigned int domcr_flags)
>      tsc_set_info(d, TSC_MODE_DEFAULT, 0UL, 0, 0);
>      spin_lock_init(&d->arch.vtsc_lock);
>  
> +    /* Allocate CQM RMID for guest */
> +    d->arch.pqos_cqm_rmid = 0;
> +    if ( system_supports_cqm() && !!(domcr_flags & DOMCRF_pqos_cqm) )

The !! is redundant here as far as the logical test goes.

> +        alloc_cqm_rmid(d);
> +
>      return 0;
>  
>   fail:
> @@ -612,6 +618,9 @@ void arch_domain_destroy(struct domain *d)
>  
>      free_xenheap_page(d->shared_info);
>      cleanup_domain_irq_mapping(d);
> +
> +    if ( system_supports_cqm() )

You can remove this conditional if ... (See free_cqm_rmid())

> +        free_cqm_rmid(d);
>  }
>  
>  unsigned long pv_guest_cr4_fixup(const struct vcpu *v, unsigned long guest_cr4)
> diff --git a/xen/arch/x86/pqos.c b/xen/arch/x86/pqos.c
> index e6ab416..e294799 100644
> --- a/xen/arch/x86/pqos.c
> +++ b/xen/arch/x86/pqos.c
> @@ -20,6 +20,8 @@
>   */
>  #include <asm/processor.h>
>  #include <xen/init.h>
> +#include <xen/spinlock.h>
> +#include <xen/sched.h>
>  #include <asm/pqos.h>
>  
>  static bool_t pqos_enabled = 1;
> @@ -29,6 +31,7 @@ unsigned int cqm_res_count = 0;
>  unsigned int cqm_upscaling_factor = 0;
>  bool_t cqm_enabled = 0;
>  struct cqm_res_struct *cqm_res_array = NULL;
> +static DEFINE_SPINLOCK(cqm_lock);
>  
>  static void __init init_cqm(void)
>  {
> @@ -78,6 +81,62 @@ void __init init_platform_qos(void)
>      init_qos_monitor();
>  }
>  
> +bool_t system_supports_cqm(void)
> +{
> +    return cqm_enabled;
> +}
> +
> +int alloc_cqm_rmid(struct domain *d)
> +{
> +    int rmid, rc = 0;
> +    unsigned long flags;
> +
> +    ASSERT(system_supports_cqm());
> +
> +    spin_lock_irqsave(&cqm_lock, flags);
> +    /* RMID=0 is reserved, enumerate from 1 */
> +    for ( rmid = 1; rmid < cqm_res_count; rmid++ )
> +    {
> +        if ( cqm_res_array[rmid].inuse)
> +            continue;
> +
> +        cqm_res_array[rmid].inuse = 1;
> +        cqm_res_array[rmid].domain_id = d->domain_id;
> +        break;
> +    }
> +    spin_unlock_irqrestore(&cqm_lock, flags);
> +
> +    /* No CQM RMID available, assign RMID=0 by default */
> +    if ( rmid == cqm_res_count )
> +    {
> +        rmid = 0;
> +        rc = -1;
> +    }
> +
> +    d->arch.pqos_cqm_rmid = rmid;
> +
> +    return rc;
> +}
> +
> +void free_cqm_rmid(struct domain *d)
> +{
> +    int rmid = d->arch.pqos_cqm_rmid;
> +    unsigned long flags;
> +
> +    ASSERT(system_supports_cqm());

... you remove this assertion and have a return early if rmid is 0.

> +
> +    spin_lock_irqsave(&cqm_lock, flags);
> +    /* We do not free system reserved "RMID=0" */
> +    if ( rmid > 0 )
> +    {
> +        cqm_res_array[rmid].inuse = 0;
> +        cqm_res_array[rmid].domain_id = 0;

Would DOMID_INVALID be more appropriate here? 0 is valid domain
identifier.  It would also mean that you could remove the inuse flag
from the structure, and the structure itself degrades to an array of
domid_t's

You can then further use cmpxchg() and avoid the spinlock.

I guess this all depends on whether you are expecting to add new
information into the structure or not.

> +    }
> +    spin_unlock_irqrestore(&cqm_lock, flags);
> +
> +    d->arch.pqos_cqm_rmid = 0;
> +}
> +
>  /*
>   * Local variables:
>   * mode: C
> diff --git a/xen/common/domctl.c b/xen/common/domctl.c
> index 904d27b..1c2e320 100644
> --- a/xen/common/domctl.c
> +++ b/xen/common/domctl.c
> @@ -425,7 +425,8 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
>                 | XEN_DOMCTL_CDF_pvh_guest
>                 | XEN_DOMCTL_CDF_hap
>                 | XEN_DOMCTL_CDF_s3_integrity
> -               | XEN_DOMCTL_CDF_oos_off)) )
> +               | XEN_DOMCTL_CDF_oos_off
> +               | XEN_DOMCTL_CDF_pqos_cqm)) )
>              break;
>  
>          dom = op->domain;
> @@ -467,6 +468,8 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl)
>              domcr_flags |= DOMCRF_s3_integrity;
>          if ( op->u.createdomain.flags & XEN_DOMCTL_CDF_oos_off )
>              domcr_flags |= DOMCRF_oos_off;
> +        if ( op->u.createdomain.flags & XEN_DOMCTL_CDF_pqos_cqm )
> +            domcr_flags |= DOMCRF_pqos_cqm;
>  
>          d = domain_create(dom, domcr_flags, op->u.createdomain.ssidref);
>          if ( IS_ERR(d) )
> diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
> index 9d39061..b0479aa 100644
> --- a/xen/include/asm-x86/domain.h
> +++ b/xen/include/asm-x86/domain.h
> @@ -313,6 +313,8 @@ struct arch_domain
>      spinlock_t e820_lock;
>      struct e820entry *e820;
>      unsigned int nr_e820;
> +
> +    int pqos_cqm_rmid;       /* CQM RMID assigned to the domain */
>  } __cacheline_aligned;
>  
>  #define has_arch_pdevs(d)    (!list_empty(&(d)->arch.pdev_list))
> diff --git a/xen/include/asm-x86/pqos.h b/xen/include/asm-x86/pqos.h
> index 934d68a..88de139 100644
> --- a/xen/include/asm-x86/pqos.h
> +++ b/xen/include/asm-x86/pqos.h
> @@ -34,4 +34,8 @@ struct cqm_res_struct {
>  
>  void init_platform_qos(void);
>  
> +bool_t system_supports_cqm(void);
> +int alloc_cqm_rmid(struct domain *);
> +void free_cqm_rmid(struct domain *);

Please use a variable in the function declaration.  "d" would suffice.

~Andrew

> +
>  #endif
> diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
> index 01a3652..47a850a 100644
> --- a/xen/include/public/domctl.h
> +++ b/xen/include/public/domctl.h
> @@ -62,6 +62,9 @@ struct xen_domctl_createdomain {
>   /* Is this a PVH guest (as opposed to an HVM or PV guest)? */
>  #define _XEN_DOMCTL_CDF_pvh_guest     4
>  #define XEN_DOMCTL_CDF_pvh_guest      (1U<<_XEN_DOMCTL_CDF_pvh_guest)
> + /* Enable pqos-cqm? */
> +#define _XEN_DOMCTL_CDF_pqos_cqm      5
> +#define XEN_DOMCTL_CDF_pqos_cqm       (1U<<_XEN_DOMCTL_CDF_pqos_cqm)
>      uint32_t flags;
>  };
>  typedef struct xen_domctl_createdomain xen_domctl_createdomain_t;
> diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
> index cbdf377..3a42656 100644
> --- a/xen/include/xen/sched.h
> +++ b/xen/include/xen/sched.h
> @@ -507,6 +507,9 @@ struct domain *domain_create(
>   /* DOMCRF_pvh: Create PV domain in HVM container. */
>  #define _DOMCRF_pvh             5
>  #define DOMCRF_pvh              (1U<<_DOMCRF_pvh)
> + /* DOMCRF_pqos_cqm: Create a domain with CQM support */
> +#define _DOMCRF_pqos_cqm        6
> +#define DOMCRF_pqos_cqm         (1U<<_DOMCRF_pqos_cqm)
>  
>  /*
>   * rcu_lock_domain_by_id() is more efficient than get_domain_by_id().