Re: [PATCH v4 08/12] x86: dynamically get/set CBM for a domain

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

On 09/04/2015 10:18, Chao Peng wrote:
> For CAT, COS is maintained in hypervisor only while CBM is exposed to
> user space directly to allow getting/setting domain's cache capacity.
> For each specified CBM, hypervisor will either use a existed COS which
> has the same CBM or allocate a new one if the same CBM is not found. If
> the allocation fails because of no enough COS available then error is
> returned. The getting/setting are always operated on a specified socket.
> For multiple sockets system, the interface may be called several times.
>
> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
> ---
>  xen/arch/x86/domctl.c           |  18 ++++++
>  xen/arch/x86/psr.c              | 126 ++++++++++++++++++++++++++++++++++++++++
>  xen/include/asm-x86/msr-index.h |   1 +
>  xen/include/asm-x86/psr.h       |   2 +
>  xen/include/public/domctl.h     |  12 ++++
>  5 files changed, 159 insertions(+)
>
> diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
> index d4f6ccf..89a6b33 100644
> --- a/xen/arch/x86/domctl.c
> +++ b/xen/arch/x86/domctl.c
> @@ -1326,6 +1326,24 @@ long arch_do_domctl(
>          }
>          break;
>  
> +    case XEN_DOMCTL_psr_cat_op:
> +        switch ( domctl->u.psr_cat_op.cmd )
> +        {
> +        case XEN_DOMCTL_PSR_CAT_OP_SET_L3_CBM:
> +            ret = psr_set_l3_cbm(d, domctl->u.psr_cat_op.target,
> +                                 domctl->u.psr_cat_op.data);
> +            break;

As I have just fixed up the style everywhere else in arch_do_domctl(),
could you put a newline in here, just to visually separate the case
statements slightly.

> +        case XEN_DOMCTL_PSR_CAT_OP_GET_L3_CBM:
> +            ret = psr_get_l3_cbm(d, domctl->u.psr_cat_op.target,
> +                                 &domctl->u.psr_cat_op.data);
> +            copyback = 1;
> +            break;
> +        default:
> +            ret = -EOPNOTSUPP;
> +            break;
> +        }
> +        break;
> +
>      default:
>          ret = iommu_do_domctl(domctl, d, u_domctl);
>          break;
> diff --git a/xen/arch/x86/psr.c b/xen/arch/x86/psr.c
> index e390fd9..5247bcd 100644
> --- a/xen/arch/x86/psr.c
> +++ b/xen/arch/x86/psr.c
> @@ -56,6 +56,17 @@ static unsigned int get_socket_count(void)
>      return DIV_ROUND_UP(nr_cpu_ids, cpus_per_socket);
>  }
>  
> +static unsigned int get_socket_cpu(unsigned int socket)
> +{
> +    if ( socket < nr_sockets )
> +    {
> +        cpumask_t *cpu_mask = cat_socket_info[socket].socket_cpu_mask;

Blank line between variables and code please.

> +        ASSERT(cpu_mask != NULL);
> +        return cpumask_any(cpu_mask);
> +    }
> +    return nr_cpu_ids;
> +}
> +
>  static void __init parse_psr_bool(char *s, char *value, char *feature,
>                                    unsigned int mask)
>  {
> @@ -252,6 +263,121 @@ int psr_get_cat_l3_info(unsigned int socket, uint32_t *cbm_len,
>      return 0;
>  }
>  
> +int psr_get_l3_cbm(struct domain *d, unsigned int socket, uint64_t *cbm)
> +{
> +    unsigned int cos;
> +    struct psr_cat_socket_info *info;
> +    int ret = get_cat_socket_info(socket, &info);
> +
> +    if ( ret )
> +        return ret;
> +
> +    cos = d->arch.psr_cos_ids[socket];
> +    *cbm = info->cos_cbm_map[cos].cbm;
> +    return 0;
> +}
> +
> +static bool_t psr_check_cbm(unsigned int cbm_len, uint64_t cbm)
> +{
> +    unsigned int first_bit, zero_bit;
> +
> +    /* Set bits should only in the range of [0, cbm_len). */
> +    if ( cbm & (~0ull << cbm_len) )
> +        return 0;
> +
> +    first_bit = find_first_bit(&cbm, cbm_len);
> +    zero_bit = find_next_zero_bit(&cbm, cbm_len, first_bit);
> +
> +    /* Set bits should be contiguous. */
> +    if ( zero_bit < cbm_len &&
> +         find_next_bit(&cbm, cbm_len, zero_bit) < cbm_len )
> +        return 0;
> +
> +    return 1;
> +}
> +
> +struct cos_cbm_info
> +{
> +    unsigned int cos;
> +    uint64_t cbm;
> +};
> +
> +static void do_write_l3_cbm(void *data)
> +{
> +    struct cos_cbm_info *info = data;

And again here please.

> +    wrmsrl(MSR_IA32_PSR_L3_MASK(info->cos), info->cbm);
> +}
> +
> +static int write_l3_cbm(unsigned int socket, unsigned int cos, uint64_t cbm)
> +{
> +    struct cos_cbm_info info = { .cos = cos, .cbm = cbm };
> +
> +    if ( socket == cpu_to_socket(smp_processor_id()) )
> +        do_write_l3_cbm(&info);
> +    else
> +    {
> +        unsigned int cpu = get_socket_cpu(socket);
> +
> +        if ( cpu >= nr_cpu_ids )
> +            return -EBADSLT;
> +        on_selected_cpus(cpumask_of(cpu), do_write_l3_cbm, &info, 1);
> +    }
> +
> +    return 0;
> +}
> +
> +int psr_set_l3_cbm(struct domain *d, unsigned int socket, uint64_t cbm)
> +{
> +    unsigned int old_cos, cos;
> +    struct psr_cat_cbm *map, *find;
> +    struct psr_cat_socket_info *info;
> +    int ret = get_cat_socket_info(socket, &info);
> +
> +    if ( ret )
> +        return ret;
> +
> +    if ( !psr_check_cbm(info->cbm_len, cbm) )
> +        return -EINVAL;
> +
> +    old_cos = d->arch.psr_cos_ids[socket];
> +    map = info->cos_cbm_map;
> +    find = NULL;
> +
> +    for ( cos = 0; cos <= info->cos_max; cos++ )
> +    {
> +        /* If still not found, then keep unused one. */
> +        if ( !find && cos != 0 && map[cos].ref == 0 )
> +            find = map + cos;
> +        else if ( map[cos].cbm == cbm )
> +        {
> +            if ( unlikely(cos == old_cos) )
> +                return -EEXIST;
> +            find = map + cos;
> +            break;
> +        }
> +    }
> +
> +    /* If old cos is referred only by the domain, then use it. */
> +    if ( !find && map[old_cos].ref == 1 )
> +        find = map + old_cos;
> +
> +    if ( !find )
> +        return -EUSERS;
> +
> +    cos = find - map;
> +    if ( find->cbm != cbm )
> +    {
> +        ret = write_l3_cbm(socket, cos, cbm);
> +        if ( ret )
> +            return ret;
> +        find->cbm = cbm;
> +    }
> +    find->ref++;
> +    map[old_cos].ref--;

This can race with psr_free_cos() leading to corruption.  It is possible
for two different domains to be holding their own spinlock but using the
same cos index.

You definitely do need a psr/cos spinlock for safety.

~Andrew

> +    d->arch.psr_cos_ids[socket] = cos;
> +    return 0;
> +}
> +
>  /* Called with domain lock held, no psr specific lock needed */
>  static void psr_free_cos(struct domain *d)
>  {
> diff --git a/xen/include/asm-x86/msr-index.h b/xen/include/asm-x86/msr-index.h
> index 83f2f70..5425f77 100644
> --- a/xen/include/asm-x86/msr-index.h
> +++ b/xen/include/asm-x86/msr-index.h
> @@ -327,6 +327,7 @@
>  #define MSR_IA32_CMT_EVTSEL		0x00000c8d
>  #define MSR_IA32_CMT_CTR		0x00000c8e
>  #define MSR_IA32_PSR_ASSOC		0x00000c8f
> +#define MSR_IA32_PSR_L3_MASK(n)	(0x00000c90 + (n))
>  
>  /* Intel Model 6 */
>  #define MSR_P6_PERFCTR(n)		(0x000000c1 + (n))
> diff --git a/xen/include/asm-x86/psr.h b/xen/include/asm-x86/psr.h
> index 3a8a406..fb474bb 100644
> --- a/xen/include/asm-x86/psr.h
> +++ b/xen/include/asm-x86/psr.h
> @@ -54,6 +54,8 @@ void psr_ctxt_switch_to(struct domain *d);
>  
>  int psr_get_cat_l3_info(unsigned int socket, uint32_t *cbm_len,
>                          uint32_t *cos_max);
> +int psr_get_l3_cbm(struct domain *d, unsigned int socket, uint64_t *cbm);
> +int psr_set_l3_cbm(struct domain *d, unsigned int socket, uint64_t cbm);
>  
>  int psr_domain_init(struct domain *d);
>  void psr_domain_free(struct domain *d);
> diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
> index ca0e51e..9f04836 100644
> --- a/xen/include/public/domctl.h
> +++ b/xen/include/public/domctl.h
> @@ -1005,6 +1005,16 @@ struct xen_domctl_psr_cmt_op {
>  typedef struct xen_domctl_psr_cmt_op xen_domctl_psr_cmt_op_t;
>  DEFINE_XEN_GUEST_HANDLE(xen_domctl_psr_cmt_op_t);
>  
> +struct xen_domctl_psr_cat_op {
> +#define XEN_DOMCTL_PSR_CAT_OP_SET_L3_CBM     0
> +#define XEN_DOMCTL_PSR_CAT_OP_GET_L3_CBM     1
> +    uint32_t cmd;       /* IN: XEN_DOMCTL_PSR_CAT_OP_* */
> +    uint32_t target;    /* IN: socket to be operated on */
> +    uint64_t data;      /* IN/OUT */
> +};
> +typedef struct xen_domctl_psr_cat_op xen_domctl_psr_cat_op_t;
> +DEFINE_XEN_GUEST_HANDLE(xen_domctl_psr_cat_op_t);
> +
>  struct xen_domctl {
>      uint32_t cmd;
>  #define XEN_DOMCTL_createdomain                   1
> @@ -1080,6 +1090,7 @@ struct xen_domctl {
>  #define XEN_DOMCTL_setvnumainfo                  74
>  #define XEN_DOMCTL_psr_cmt_op                    75
>  #define XEN_DOMCTL_arm_configure_domain          76
> +#define XEN_DOMCTL_psr_cat_op                    77
>  #define XEN_DOMCTL_gdbsx_guestmemio            1000
>  #define XEN_DOMCTL_gdbsx_pausevcpu             1001
>  #define XEN_DOMCTL_gdbsx_unpausevcpu           1002
> @@ -1145,6 +1156,7 @@ struct xen_domctl {
>          struct xen_domctl_gdbsx_domstatus   gdbsx_domstatus;
>          struct xen_domctl_vnuma             vnuma;
>          struct xen_domctl_psr_cmt_op        psr_cmt_op;
> +        struct xen_domctl_psr_cat_op        psr_cat_op;
>          uint8_t                             pad[128];
>      } u;
>  };