linux-kernel - Re: [PATCH v4] x86/resctrl: Clear staged_config[] before and after it is used

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Message-ID: <9c0e0e7c-45e4-ad65-f9a0-2eb582a62a3d@intel.com>
Date:   Tue, 13 Dec 2022 09:54:14 -0800
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Shawn Wang <shawnwang@...ux.alibaba.com>, <fenghua.yu@...el.com>
CC:     <bp@...en8.de>, <dave.hansen@...ux.intel.com>, <hpa@...or.com>,
        <james.morse@....com>, <jamie@...iainc.com>,
        <linux-kernel@...r.kernel.org>, <mingo@...hat.com>,
        <tglx@...utronix.de>, <x86@...nel.org>
Subject: Re: [PATCH v4] x86/resctrl: Clear staged_config[] before and after it
 is used

Hi Shawn,

On 12/8/2022 6:44 PM, Shawn Wang wrote:
> 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.
> 
> Fixes: 75408e43509e ("x86/resctrl: Allow different CODE/DATA configurations to be staged")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Shawn Wang <shawnwang@...ux.alibaba.com>
> Suggested-by: Xin Hao <xhao@...ux.alibaba.com>
> ---

Thank you very much.

Tested-by: Reinette Chatre <reinette.chatre@...el.com>
Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>

Reinette