Hi Julien, > -----Original Message----- > From: Julien Grall <jul...@xen.org> > Sent: 2021年8月25日 21:24 > To: Wei Chen <wei.c...@arm.com>; xen-devel@lists.xenproject.org; > sstabell...@kernel.org > Cc: Bertrand Marquis <bertrand.marq...@arm.com> > Subject: Re: [XEN RFC PATCH 13/40] xen/arm: introduce numa_set_node for > Arm > > > > On 25/08/2021 13:07, Wei Chen wrote: > > Hi Julien, > > Hi Wei, > > >> -----Original Message----- > >> From: Julien Grall <jul...@xen.org> > >> Sent: 2021年8月25日 18:37 > >> To: Wei Chen <wei.c...@arm.com>; xen-devel@lists.xenproject.org; > >> sstabell...@kernel.org; jbeul...@suse.com > >> Cc: Bertrand Marquis <bertrand.marq...@arm.com> > >> Subject: Re: [XEN RFC PATCH 13/40] xen/arm: introduce numa_set_node for > >> Arm > >> > >> Hi Wei, > >> > >> On 11/08/2021 11:23, Wei Chen wrote: > >>> This API is used to set one CPU to a NUMA node. If the system > >>> configure NUMA off or system initialize NUMA failed, the > >>> online NUMA node would set to only node#0. This will be done > >>> in following patches. When NUMA turn off or init failed, > >>> node_online_map will be cleared and set node#0 online. So we > >>> use node_online_map to prevent to set a CPU to an offline node. > >> > >> IHMO numa_set_node() should behave exactly the same way on x86 and Arm > >> because this is going to be used by the common code. > >> > >> From the commit message, I don't quite understand why the check is > >> necessary on Arm but not on x86. Can you clarify it? > >> > > > > Yes, in patch#27, in smpboot.c, dt_smp_init_cpus function. > > We will parse CPU numa-node-id from dtb CPU node. If we get > > a valid node ID for one CPU, we will invoke numa_set_node to > > create CPU-NODE map. But in our testing, we found when NUMA > > init failed, numa_set_node still can set CPU to a offline > > or invalid NODE. So we're using node_online_map to prevent > > this behavior. Otherwise we have to check node_online_map > > everywhere before we call numa_set_node. > > What do you mean by invalid NODE? Is it 0xFF (NUMA_NO_NODE)?
No, I mean some wrong content in device tree. For example, if the dtb set a wrong numa-node-id in CPU dt-node. > > > > > x86 actually is doing the same way, but it handles node_online_map > > check out of numa_set_node: > > Right... > > >> I think numa_set_node() will want to be implemented in common code. > >> > > > > See my above comment. If x86 is ok, I think yes, we can do it > > in common code. > > ... on x86, this check is performed outside of numa_set_node() for one > caller whereas on Arm you are adding it in numa_set_node(). > > For example, numa_set_node() can be called with NUMA_NO_NODE. On x86, we > would set cpu_to_node[] to that value. However, if I am not mistaken, on > Arm we would set the value to 0. > > This will change the behavior of users to cpu_to_node() later on (such > as XEN_SYSCTL_cputopoinfo). > > NUMA is not something architecture specific, so I dont't think the > implementation should differ here. > > In this case, I think numa_set_node() shouldn't check if the node is > valid. Instead, the caller should take care of it if it is important. > Yes, I agree. I will change it in next version. > Cheers, > > -- > Julien Grall
