Re: [PATCH v5] x86/resctrl: Clear staged_config[] before and after it is used

[Reinette Chatre]

Hi x86 Maintainers,

Could you please consider this fix for inclusion?

Thank you very much

Reinette

On 1/18/2023 1:22 PM, Yu, Fenghua wrote:
>> Chatre, Reinette <reinette.chatre@xxxxxxxxx> writes
>> Sent: Tuesday, January 17, 2023 1:15 PM
>> To: Yu, Fenghua <fenghua.yu@xxxxxxxxx>; bp@xxxxxxxxx;
>> dave.hansen@xxxxxxxxxxxxxxx; tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx;
>> x86@xxxxxxxxxx
>> Cc: hpa@xxxxxxxxx; james.morse@xxxxxxx; jamie@xxxxxxxxxxxx; linux-
>> kernel@xxxxxxxxxxxxxxx; shawnwang@xxxxxxxxxxxxxxxxx; Chatre, Reinette
>> <reinette.chatre@xxxxxxxxx>
>> Subject: [PATCH v5] x86/resctrl: Clear staged_config[] before and after it is used
>>
>> From: Shawn Wang <shawnwang@xxxxxxxxxxxxxxxxx>
>>
>> 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:
>>     unchecked MSR access error: WRMSR to 0xca0 (tried to write
>> 0x00000000000007ff) at rIP: 0xffffffff82249142 (cat_wrmsr+0x32/0x60)
>>     Call Trace:
>>      <IRQ>
>>      __flush_smp_call_function_queue+0x11d/0x170
>>      __sysvec_call_function+0x24/0xd0
>>      sysvec_call_function+0x89/0xc0
>>      </IRQ>
>>      <TASK>
>>      asm_sysvec_call_function+0x16/0x20
>>
>> When creating a new resource control group, hardware will be configured by
>> the following process:
>>     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.
>>
>> [reinette: re-order commit tags]
>>
>> Fixes: 75408e43509e ("x86/resctrl: Allow different CODE/DATA configurations
>> to be staged")
>> Suggested-by: Xin Hao <xhao@xxxxxxxxxxxxxxxxx>
>> Signed-off-by: Shawn Wang <shawnwang@xxxxxxxxxxxxxxxxx>
>> Signed-off-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
>> Tested-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
>> Cc: <stable@xxxxxxxxxxxxxxx>
>> ---
>> Changes since v4:
>> - Essentially a resubmit of v4, changes limited to commit tags.
>> - v4: https://lore.kernel.org/lkml/20221209024436.22170-1-
>> shawnwang@xxxxxxxxxxxxxxxxx/
>> - No changes to patch.
>> - Only change in changelog is re-ordering of commit tags.
>> - Add Reinette's Tested-by, but change the Reviewed-by to Signed-off-by
>>   because of the change in hands of this submission.
>>
>> Changes since v3:
>> - Update the commit message suggested by Reiniette Chatre.
>> - Rename resctrl_staged_configs_clear() to rdt_staged_configs_clear().
>> - Move rdt_staged_configs_clear() to arch/x86/kernel/cpu/resctrl/internal.h.
>>
>> 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/internal.h    |  1 +
>>  arch/x86/kernel/cpu/resctrl/rdtgroup.c    | 25 +++++++++++++++++++----
>>  3 files changed, 24 insertions(+), 9 deletions(-)
>>
>> diff --git a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
>> b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
>> index 1df0e3262bca..bcdc679dad4e 100644
>> --- a/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
>> +++ b/arch/x86/kernel/cpu/resctrl/ctrlmondata.c
>> @@ -373,7 +373,6 @@ 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;
>> @@ -402,10 +401,7 @@ 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));
>> -	}
>> +	rdt_staged_configs_clear();
>>
>>  	while ((tok = strsep(&buf, "\n")) != NULL) {
>>  		resname = strim(strsep(&tok, ":"));
>> @@ -450,6 +446,7 @@ ssize_t rdtgroup_schemata_write(struct
>> kernfs_open_file *of,
>>  	}
>>
>>  out:
>> +	rdt_staged_configs_clear();
>>  	rdtgroup_kn_unlock(of->kn);
>>  	cpus_read_unlock();
>>  	return ret ?: nbytes;
>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h
>> b/arch/x86/kernel/cpu/resctrl/internal.h
>> index 5ebd28e6aa0c..f43eb7340ca5 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -527,5 +527,6 @@ bool has_busy_rmid(struct rdt_resource *r, struct
>> rdt_domain *d);  void __check_limbo(struct rdt_domain *d, bool force_free);
>> void rdt_domain_reconfigure_cdp(struct rdt_resource *r);  void __init
>> thread_throttle_mode_init(void);
>> +void rdt_staged_configs_clear(void);
>>
>>  #endif /* _ASM_X86_RESCTRL_INTERNAL_H */ diff --git
>> a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 5993da21d822..41e89fc49d77 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -78,6 +78,19 @@ void rdt_last_cmd_printf(const char *fmt, ...)
>>  	va_end(ap);
>>  }
>>
>> +void rdt_staged_configs_clear(void)
>> +{
>> +	struct rdt_resource *r;
>> +	struct rdt_domain *dom;
>> +
>> +	lockdep_assert_held(&rdtgroup_mutex);
>> +
>> +	for_each_alloc_capable_rdt_resource(r) {
>> +		list_for_each_entry(dom, &r->domains, list)
>> +			memset(dom->staged_config, 0, sizeof(dom-
>>> staged_config));
>> +	}
>> +}
>> +
>>  /*
>>   * Trivial allocator for CLOSIDs. Since h/w only supports a small number,
>>   * we can keep a bitmap of free CLOSIDs in a single integer.
>> @@ -2851,7 +2864,9 @@ static int rdtgroup_init_alloc(struct rdtgroup *rdtgrp)
>> {
>>  	struct resctrl_schema *s;
>>  	struct rdt_resource *r;
>> -	int ret;
>> +	int ret = 0;
>> +
>> +	rdt_staged_configs_clear();
>>
>>  	list_for_each_entry(s, &resctrl_schema_all, list) {
>>  		r = s->res;
>> @@ -2862,20 +2877,22 @@ 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:
>> +	rdt_staged_configs_clear();
>> +	return ret;
>>  }
>>
>>  static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
>> --
>> 2.34.1
> 
> Reviewed-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
> 
> Thanks.
> 
> -Fenghua