[PATCH v3] x86/resctrl: Clear staged_config[] before and after it is used

Shawn Wang
2022-11-24T12:43:05Z

As a temporary storage, staged_config[] in rdt_domain should be cleared
before and after it is used. The stale value in staged_config[] could
cause an MSR access error.

Here is a reproducer on a system with 16 usable CLOSIDs for a 15-way L3
Cache (MBA should be disabled if the number of CLOSIDs for MB is less than
16.) :
mount -t resctrl resctrl -o cdp /sys/fs/resctrl
mkdir /sys/fs/resctrl/p{1..7}
umount /sys/fs/resctrl/
mount -t resctrl resctrl /sys/fs/resctrl
mkdir /sys/fs/resctrl/p{1..8}

An error occurs when creating resource group named p8:
[ 6180.939345] unchecked MSR access error: WRMSR to 0xca0 (tried to write
0x00000000000007ff) at rIP: 0xffffffff82249142 (cat_wrmsr+0x32/0x60)
[ 6180.951983] Call Trace:
[ 6180.954516] <IRQ>
[ 6180.956619] __flush_smp_call_function_queue+0x11d/0x170
[ 6180.962028] __sysvec_call_function+0x24/0xd0
[ 6180.966485] sysvec_call_function+0x89/0xc0
[ 6180.970760] </IRQ>
[ 6180.972947] <TASK>
[ 6180.975131] asm_sysvec_call_function+0x16/0x20

When creating a new resource control group, hardware will be configured
by resctrl_arch_update_domains():
rdtgroup_mkdir()->rdtgroup_mkdir_ctrl_mon()->rdtgroup_init_alloc()->resctrl_arch_update_domains()

resctrl_arch_update_domains() iterates and updates all resctrl_conf_type
whose have_new_ctrl is true. Since staged_config[] holds the same values as
when CDP was enabled, it will continue to update the CDP_CODE and CDP_DATA
configurations. When group p8 is created, get_config_index() called in
resctrl_arch_update_domains() will return 16 and 17 as the CLOSIDs for
CDP_CODE and CDP_DATA, which will be translated to an invalid register -
0xca0 in this scenario.

Fix it by clearing staged_config[] before and after it is used.

Fixes: 75408e43509ed ("x86/resctrl: Allow different CODE/DATA configurations to be staged")
Cc: <stable@vger.kernel.org>
Signed-off-by: Shawn Wang <shawnwang@linux.alibaba.com>
Suggested-by: Xin Hao <xhao@linux.alibaba.com>
---
Changes since v2:
- Update the commit message suggested by Reiniette Chatre.
- Make the clearing work more robust.

Changes since v1:
- Move the clearing from schemata_list_destroy() to resctrl_arch_update_domains().
- Update the commit message suggested by Reiniette Chatre.
- Add stable tag suggested by James Morse.
---
arch/x86/kernel/cpu/resctrl/ctrlmondata.c | 7 ++-----
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 23 +++++++++++++++++++----
include/linux/resctrl.h | 2 ++
3 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
index 1dafbdc5ac31..93d1f11a1f19 100644
--- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
+++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
@@ -374,7 +374,6 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
{
struct resctrl_schema *s;
struct rdtgroup *rdtgrp;
- struct rdt_domain *dom;
struct rdt_resource *r;
char *tok, *resname;
int ret = 0;
@@ -403,10 +402,7 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
goto out;
}

- list_for_each_entry(s, &resctrl_schema_all, list) {
- list_for_each_entry(dom, &s->res->domains, list)
- memset(dom->staged_config, 0, sizeof(dom->staged_config));
- }
+ resctrl_staged_configs_clear();

while ((tok = strsep(&buf, "\n")) != NULL) {
resname = strim(strsep(&tok, ":"));
@@ -451,6 +447,7 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
}

out:
+ resctrl_staged_configs_clear();
rdtgroup_kn_unlock(of->kn);
cpus_read_unlock();
return ret ?: nbytes;
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index e5a48f05e787..fa00eafd3cd8 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -2841,7 +2841,9 @@ static int rdtgroup_init_alloc(struct rdtgroup *rdtgrp)
{
struct resctrl_schema *s;
struct rdt_resource *r;
- int ret;
+ int ret = 0;
+
+ resctrl_staged_configs_clear();

list_for_each_entry(s, &resctrl_schema_all, list) {
r = s->res;
@@ -2852,20 +2854,22 @@ static int rdtgroup_init_alloc(struct rdtgroup *rdtgrp)
} else {
ret = rdtgroup_init_cat(s, rdtgrp->closid);
if (ret < 0)
- return ret;
+ goto out;
}

ret = resctrl_arch_update_domains(r, rdtgrp->closid);
if (ret < 0) {
rdt_last_cmd_puts("Failed to initialize allocations\n");
- return ret;
+ goto out;
}

}

rdtgrp->mode = RDT_MODE_SHAREABLE;

- return 0;
+out:
+ resctrl_staged_configs_clear();
+ return ret;
}

static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
@@ -3380,6 +3384,17 @@ int resctrl_online_domain(struct rdt_resource *r, struct rdt_domain *d)
return 0;
}

+void resctrl_staged_configs_clear(void)
+{
+ struct rdt_resource *r;
+ struct rdt_domain *dom;
+
+ for_each_alloc_capable_rdt_resource(r) {
+ list_for_each_entry(dom, &r->domains, list)
+ memset(dom->staged_config, 0, sizeof(dom->staged_config));
+ }
+}
+
/*
* rdtgroup_init - rdtgroup initialization
*
diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
index 0cf5b20c6ddf..2f7af447eaf2 100644
--- a/include/linux/resctrl.h
+++ b/include/linux/resctrl.h
@@ -250,6 +250,8 @@ int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
void resctrl_arch_reset_rmid(struct rdt_resource *r, struct rdt_domain *d,
u32 rmid, enum resctrl_event_id eventid);

+void resctrl_staged_configs_clear(void);
+
extern unsigned int resctrl_rmid_realloc_threshold;
extern unsigned int resctrl_rmid_realloc_limit;

--
2.27.0