Re: [PATCH v4 10/23] libxl: remove get_all_assigned_devices() from libxl_pci.c

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>]

Hi, Paul!

On 11/24/20 10:01 AM, Paul Durrant wrote:
> From: Paul Durrant <pdurrant@xxxxxxxxxx>
>
> Use of this function is a very inefficient way to check whether a device
> has already been assigned.
>
> This patch adds code that saves the domain id in xenstore at the point of
> assignment, and removes it again when the device id de-assigned (or the
> domain is destroyed). It is then straightforward to check whether a device
> has been assigned by checking whether a device has a saved domain id.
>
> NOTE: To facilitate the xenstore check it is necessary to move the
>        pci_info_xs_read() earlier in libxl_pci.c. To keep related functions
>        together, the rest of the pci_info_xs_XXX() functions are moved too.
>
> Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

Thank you,

Oleksandr

> ---
> Cc: Ian Jackson <iwj@xxxxxxxxxxxxxx>
> Cc: Wei Liu <wl@xxxxxxx>
> ---
>   tools/libs/light/libxl_pci.c | 149 
> ++++++++++++++++---------------------------
>   1 file changed, 55 insertions(+), 94 deletions(-)
>
> diff --git a/tools/libs/light/libxl_pci.c b/tools/libs/light/libxl_pci.c
> index ec101f255f..d3c7a547c3 100644
> --- a/tools/libs/light/libxl_pci.c
> +++ b/tools/libs/light/libxl_pci.c
> @@ -336,50 +336,6 @@ retry_transaction2:
>       return 0;
>   }
>   
> -static int get_all_assigned_devices(libxl__gc *gc, libxl_device_pci **list, 
> int *num)
> -{
> -    char **domlist;
> -    unsigned int nd = 0, i;
> -
> -    *list = NULL;
> -    *num = 0;
> -
> -    domlist = libxl__xs_directory(gc, XBT_NULL, "/local/domain", &nd);
> -    for(i = 0; i < nd; i++) {
> -        char *path, *num_devs;
> -
> -        path = GCSPRINTF("/local/domain/0/backend/%s/%s/0/num_devs",
> -                         
> libxl__device_kind_to_string(LIBXL__DEVICE_KIND_PCI),
> -                         domlist[i]);
> -        num_devs = libxl__xs_read(gc, XBT_NULL, path);
> -        if ( num_devs ) {
> -            int ndev = atoi(num_devs), j;
> -            char *devpath, *bdf;
> -
> -            for(j = 0; j < ndev; j++) {
> -                devpath = GCSPRINTF("/local/domain/0/backend/%s/%s/0/dev-%u",
> -                                    
> libxl__device_kind_to_string(LIBXL__DEVICE_KIND_PCI),
> -                                    domlist[i], j);
> -                bdf = libxl__xs_read(gc, XBT_NULL, devpath);
> -                if ( bdf ) {
> -                    unsigned dom, bus, dev, func;
> -                    if ( sscanf(bdf, PCI_BDF, &dom, &bus, &dev, &func) != 4 )
> -                        continue;
> -
> -                    *list = realloc(*list, sizeof(libxl_device_pci) * 
> ((*num) + 1));
> -                    if (*list == NULL)
> -                        return ERROR_NOMEM;
> -                    pci_struct_fill(*list + *num, dom, bus, dev, func, 0);
> -                    (*num)++;
> -                }
> -            }
> -        }
> -    }
> -    libxl__ptr_add(gc, *list);
> -
> -    return 0;
> -}
> -
>   static int is_pci_in_array(libxl_device_pci *assigned, int num_assigned,
>                              int dom, int bus, int dev, int func)
>   {
> @@ -427,19 +383,58 @@ static int sysfs_write_bdf(libxl__gc *gc, const char * 
> sysfs_path,
>       return 0;
>   }
>   
> +#define PCI_INFO_PATH "/libxl/pci"
> +
> +static char *pci_info_xs_path(libxl__gc *gc, libxl_device_pci *pci,
> +                              const char *node)
> +{
> +    return node ?
> +        GCSPRINTF(PCI_INFO_PATH"/"PCI_BDF_XSPATH"/%s",
> +                  pci->domain, pci->bus, pci->dev, pci->func,
> +                  node) :
> +        GCSPRINTF(PCI_INFO_PATH"/"PCI_BDF_XSPATH,
> +                  pci->domain, pci->bus, pci->dev, pci->func);
> +}
> +
> +
> +static int pci_info_xs_write(libxl__gc *gc, libxl_device_pci *pci,
> +                              const char *node, const char *val)
> +{
> +    char *path = pci_info_xs_path(gc, pci, node);
> +    int rc = libxl__xs_printf(gc, XBT_NULL, path, "%s", val);
> +
> +    if (rc) LOGE(WARN, "Write of %s to node %s failed.", val, path);
> +
> +    return rc;
> +}
> +
> +static char *pci_info_xs_read(libxl__gc *gc, libxl_device_pci *pci,
> +                              const char *node)
> +{
> +    char *path = pci_info_xs_path(gc, pci, node);
> +
> +    return libxl__xs_read(gc, XBT_NULL, path);
> +}
> +
> +static void pci_info_xs_remove(libxl__gc *gc, libxl_device_pci *pci,
> +                               const char *node)
> +{
> +    char *path = pci_info_xs_path(gc, pci, node);
> +    libxl_ctx *ctx = libxl__gc_owner(gc);
> +
> +    /* Remove the xenstore entry */
> +    xs_rm(ctx->xsh, XBT_NULL, path);
> +}
> +
>   libxl_device_pci *libxl_device_pci_assignable_list(libxl_ctx *ctx, int *num)
>   {
>       GC_INIT(ctx);
> -    libxl_device_pci *pcis = NULL, *new, *assigned;
> +    libxl_device_pci *pcis = NULL, *new;
>       struct dirent *de;
>       DIR *dir;
> -    int r, num_assigned;
>   
>       *num = 0;
>   
> -    r = get_all_assigned_devices(gc, &assigned, &num_assigned);
> -    if (r) goto out;
> -
>       dir = opendir(SYSFS_PCIBACK_DRIVER);
>       if (NULL == dir) {
>           if (errno == ENOENT) {
> @@ -455,9 +450,6 @@ libxl_device_pci 
> *libxl_device_pci_assignable_list(libxl_ctx *ctx, int *num)
>           if (sscanf(de->d_name, PCI_BDF, &dom, &bus, &dev, &func) != 4)
>               continue;
>   
> -        if (is_pci_in_array(assigned, num_assigned, dom, bus, dev, func))
> -            continue;
> -
>           new = realloc(pcis, ((*num) + 1) * sizeof(*new));
>           if (NULL == new)
>               continue;
> @@ -467,6 +459,10 @@ libxl_device_pci 
> *libxl_device_pci_assignable_list(libxl_ctx *ctx, int *num)
>   
>           memset(new, 0, sizeof(*new));
>           pci_struct_fill(new, dom, bus, dev, func, 0);
> +
> +        if (pci_info_xs_read(gc, new, "domid")) /* already assigned */
> +            continue;
> +
>           (*num)++;
>       }
>   
> @@ -737,48 +733,6 @@ static int pciback_dev_unassign(libxl__gc *gc, 
> libxl_device_pci *pci)
>       return 0;
>   }
>   
> -#define PCI_INFO_PATH "/libxl/pci"
> -
> -static char *pci_info_xs_path(libxl__gc *gc, libxl_device_pci *pci,
> -                              const char *node)
> -{
> -    return node ?
> -        GCSPRINTF(PCI_INFO_PATH"/"PCI_BDF_XSPATH"/%s",
> -                  pci->domain, pci->bus, pci->dev, pci->func,
> -                  node) :
> -        GCSPRINTF(PCI_INFO_PATH"/"PCI_BDF_XSPATH,
> -                  pci->domain, pci->bus, pci->dev, pci->func);
> -}
> -
> -
> -static void pci_info_xs_write(libxl__gc *gc, libxl_device_pci *pci,
> -                              const char *node, const char *val)
> -{
> -    char *path = pci_info_xs_path(gc, pci, node);
> -
> -    if ( libxl__xs_printf(gc, XBT_NULL, path, "%s", val) < 0 ) {
> -        LOGE(WARN, "Write of %s to node %s failed.", val, path);
> -    }
> -}
> -
> -static char *pci_info_xs_read(libxl__gc *gc, libxl_device_pci *pci,
> -                              const char *node)
> -{
> -    char *path = pci_info_xs_path(gc, pci, node);
> -
> -    return libxl__xs_read(gc, XBT_NULL, path);
> -}
> -
> -static void pci_info_xs_remove(libxl__gc *gc, libxl_device_pci *pci,
> -                               const char *node)
> -{
> -    char *path = pci_info_xs_path(gc, pci, node);
> -    libxl_ctx *ctx = libxl__gc_owner(gc);
> -
> -    /* Remove the xenstore entry */
> -    xs_rm(ctx->xsh, XBT_NULL, path);
> -}
> -
>   static int libxl__device_pci_assignable_add(libxl__gc *gc,
>                                               libxl_device_pci *pci,
>                                               int rebind)
> @@ -1594,6 +1548,9 @@ void libxl__device_pci_add(libxl__egc *egc, uint32_t 
> domid,
>           goto out;
>       }
>   
> +    rc = pci_info_xs_write(gc, pci, "domid", GCSPRINTF("%u", domid));
> +    if (rc) goto out;
> +
>       libxl__device_pci_reset(gc, pci->domain, pci->bus, pci->dev, pci->func);
>   
>       stubdomid = libxl_get_stubdom_id(ctx, domid);
> @@ -1721,6 +1678,7 @@ static void device_pci_add_done(libxl__egc *egc,
>                "PCI device %x:%x:%x.%x (rc %d)",
>                pci->domain, pci->bus, pci->dev, pci->func,
>                rc);
> +        pci_info_xs_remove(gc, pci, "domid");
>       }
>       aodev->rc = rc;
>       aodev->callback(egc, aodev);
> @@ -2282,6 +2240,9 @@ out:
>       libxl__xswait_stop(gc, &prs->xswait);
>       libxl__ev_time_deregister(gc, &prs->timeout);
>       libxl__ev_time_deregister(gc, &prs->retry_timer);
> +
> +    if (!rc) pci_info_xs_remove(gc, pci, "domid");
> +
>       aodev->rc = rc;
>       aodev->callback(egc, aodev);
>   }