Re: [PATCH v13 24/27] x86/resctrl: Introduce the interface to modify assignments in a group

[Peter Newman <peternewman@google.com>]

Hi Babu,

On Fri, May 16, 2025 at 12:56 AM Babu Moger <babu.moger@amd.com> wrote:

> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
> index 8d970b99bbbd..ea1782723f81 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -2126,6 +2126,168 @@ static int mbm_L3_assignments_show(struct kernfs_open_file *of, struct seq_file
>         return ret;
>  }
>
> +/*
> + * mbm_get_mon_event_by_name() - Return the mon_evt entry for the matching
> + * event name.
> + */
> +static struct mon_evt *mbm_get_mon_event_by_name(struct rdt_resource *r,
> +                                                char *name)
> +{
> +       struct mon_evt *mevt;
> +
> +       list_for_each_entry(mevt, &r->mon.evt_list, list) {
> +               if (!strcmp(mevt->name, name))
> +                       return mevt;
> +       }
> +
> +       return NULL;
> +}
> +
> +static unsigned int resctrl_get_assing_type(char *assign)
> +{
> +       unsigned int mon_state = ASSIGN_NONE;
> +       int len = strlen(assign);

[  395.013183] BUG: kernel NULL pointer dereference, address: 0000000000000000
[  395.013426] #PF: supervisor read access in kernel mode
[  395.013600] #PF: error_code(0x0000) - not-present page
[  395.013779] PGD 39322c067 P4D 2a4f49067 PUD 2a4f4a067 PMD 0
[  395.013973] Oops: Oops: 0000 [#1] SMP DEBUG_PAGEALLOC NOPTI
[  395.014156] CPU: 37 UID: 0 PID: 24147 Comm: bash Not tainted
6.15.0-dbg-DEV #13 NONE
[  395.014403] Hardware name: Google Astoria-Turin/astoria, BIOS
0.20241223.2-0 01/17/2025
[  395.014652] RIP: 0010:strlen+0xb/0x20
[  395.014778] Code: 66 66 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 90
90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 c7 c0 ff
ff ff ff <80> 7c 07 01 00 48 8d 40 01 75 f5 c3 cc cc cc cc cc 0f 1f 40
00 90
[  395.015356] RSP: 0018:ffa000002f743d58 EFLAGS: 00010246
[  395.015522] RAX: ffffffffffffffff RBX: ff11000129a00600 RCX: 0000000000000000
[  395.015747] RDX: ff110001299f5253 RSI: ffffffff827b9651 RDI: 0000000000000000
[  395.015968] RBP: 0000000000000000 R08: 000000000000003d R09: 0000000000000000
[  395.016202] R10: ffffffff827b9652 R11: 0000000000000000 R12: ffffffff8305b7f8
[  395.016421] R13: ff110001299f5240 R14: 0000000000000014 R15: 0000000000000000
[  395.016644] FS:  00007f1281ff8b80(0000) GS:ff1100bdc8276000(0000)
knlGS:0000000000000000
[  395.016893] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  395.017071] CR2: 0000000000000000 CR3: 0000000420bc8002 CR4: 0000000000771ef0
[  395.017298] PKRU: 55555554
[  395.017388] Call Trace:
[  395.017471]  <TASK>
[  395.017545]  mbm_L3_assignments_write+0x2d4/0x4e0
[  395.017700]  kernfs_fop_write_iter+0x132/0x1c0
[  395.017851]  vfs_write+0x2bf/0x3c0
[  395.017963]  ksys_write+0x82/0x100
[  395.018074]  do_syscall_64+0xee/0x210
[  395.018198]  ? exc_page_fault+0x81/0xe0
[  395.018321]  entry_SYSCALL_64_after_hwframe+0x77/0x7f
[  395.018482] RIP: 0033:0x7f128177f8b3
[  395.018598] Code: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc
cc cc cc cc cc cc cc 48 8b 05 99 91 07 00 83 38 00 75 10 b8 01 00 00
00 0f 05 <48> 3d 01 f0 ff ff 73 4d c3 55 48 89 e5 41 57 41 56 53 50 48
89 d3
[  395.019167] RSP: 002b:00007ffff66e80f8 EFLAGS: 00000246 ORIG_RAX:
0000000000000001
[  395.019409] RAX: ffffffffffffffda RBX: 0000000000000014 RCX: 00007f128177f8b3
[  395.019636] RDX: 0000000000000014 RSI: 0000000001eedb60 RDI: 0000000000000001
[  395.019861] RBP: 00007ffff66e8120 R08: 0000000000000000 R09: 0000000000000000
[  395.020081] R10: 00007ffff66e81b0 R11: 0000000000000246 R12: 0000000001eedb60
[  395.020303] R13: 0000000000000001 R14: 00007f12817fa650 R15: 0000000000000014
[  395.020532]  </TASK>

> +
> +       if (!len || len > 1)
> +               return ASSIGN_INVALID;
> +
> +       switch (*assign) {
> +       case 'e':
> +               mon_state = ASSIGN_EXCLUSIVE;
> +               break;
> +       case '_':
> +               mon_state = ASSIGN_NONE;
> +               break;
> +       default:
> +               mon_state = ASSIGN_INVALID;
> +               break;
> +       }
> +
> +       return mon_state;
> +}
> +
> +static int resctrl_process_assign(struct rdt_resource *r, struct rdtgroup *rdtgrp,
> +                                 char *config, char *tok)
> +{
> +       struct rdt_mon_domain *d;
> +       char *dom_str, *id_str;
> +       unsigned long dom_id = 0;
> +       struct mon_evt *mevt;
> +       int assign_type;
> +       char domain[10];
> +       bool found;
> +       int ret;
> +
> +       mevt = mbm_get_mon_event_by_name(r, config);
> +       if (!mevt) {
> +               rdt_last_cmd_printf("Invalid assign configuration %s\n", config);
> +               return  -ENOENT;
> +       }
> +
> +next:
> +       if (!tok || tok[0] == '\0')
> +               return 0;
> +
> +       /* Start processing the strings for each domain */
> +       dom_str = strim(strsep(&tok, ";"));
> +
> +       id_str = strsep(&dom_str, "=");

If there's no '=' then dom_str becomes NULL...

> +
> +       /* Check for domain id '*' which means all domains */
> +       if (id_str && *id_str == '*') {
> +               d = NULL;
> +               goto check_state;
> +       } else if (!id_str || kstrtoul(id_str, 10, &dom_id)) {
> +               rdt_last_cmd_puts("Missing domain id\n");
> +               return -EINVAL;
> +       }
> +
> +       /* Verify if the dom_id is valid */
> +       found = false;
> +       list_for_each_entry(d, &r->mon_domains, hdr.list) {
> +               if (d->hdr.id == dom_id) {
> +                       found = true;
> +                       break;
> +               }
> +       }
> +
> +       if (!found) {
> +               rdt_last_cmd_printf("Invalid domain id %ld\n", dom_id);
> +               return -EINVAL;
> +       }
> +
> +check_state:
> +       assign_type = resctrl_get_assing_type(dom_str);

then the resulting type of whatever this is supposed to mean is "panic"

Thanks,
-Peter