Hi Henry. On 20/05/2024 04:57, Henry Wang wrote: > Hi All, > > Gentle ping since it has been a couple of months, any comments on this > updated patch? Thanks! Sorry for the late reply.
> > Kind regards, > Henry > > On 3/21/2024 11:57 AM, Henry Wang wrote: >> In the common sysctl command XEN_SYSCTL_physinfo, the value of >> cores_per_socket is calculated based on the cpu_core_mask of CPU0. >> Currently on Arm this is a fixed value 1 (can be checked via xl info), >> which is not correct. This is because during the Arm CPU online >> process at boot time, setup_cpu_sibling_map() only sets the per-cpu >> cpu_core_mask for itself. >> >> cores_per_socket refers to the number of cores that belong to the same >> socket (NUMA node). Currently Xen on Arm does not support physical >> CPU hotplug and NUMA, also we assume there is no multithread. Therefore >> cores_per_socket means all possible CPUs detected from the device >> tree. Setting the per-cpu cpu_core_mask in setup_cpu_sibling_map() >> accordingly. Modify the in-code comment which seems to be outdated. Add >> a warning to users if Xen is running on processors with multithread >> support. >> >> Signed-off-by: Henry Wang <[email protected]> >> Signed-off-by: Henry Wang <[email protected]> Reviewed-by: Michal Orzel <[email protected]> >> --- >> v3: >> - Use cpumask_copy() to set cpu_core_mask and drop the unnecessary >> cpumask_set_cpu(cpu, per_cpu(cpu_core_mask, cpu)). >> - In-code comment adjustments. >> - Add a warning for multithread. >> v2: >> - Do not do the multithread check. >> --- >> xen/arch/arm/smpboot.c | 18 +++++++++++++++--- >> 1 file changed, 15 insertions(+), 3 deletions(-) >> >> diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c >> index a84e706d77..b6268be27a 100644 >> --- a/xen/arch/arm/smpboot.c >> +++ b/xen/arch/arm/smpboot.c >> @@ -66,7 +66,11 @@ static bool cpu_is_dead; >> >> /* ID of the PCPU we're running on */ >> DEFINE_PER_CPU(unsigned int, cpu_id); >> -/* XXX these seem awfully x86ish... */ >> +/* >> + * Although multithread is part of the Arm spec, there are not many >> + * processors support multithread and current Xen on Arm assumes there NIT: s/support/supporting >> + * is no multithread. >> + */ >> /* representing HT siblings of each logical CPU */ >> DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_sibling_mask); >> /* representing HT and core siblings of each logical CPU */ >> @@ -85,9 +89,13 @@ static int setup_cpu_sibling_map(int cpu) >> !zalloc_cpumask_var(&per_cpu(cpu_core_mask, cpu)) ) >> return -ENOMEM; >> >> - /* A CPU is a sibling with itself and is always on its own core. */ >> + /* >> + * Currently we assume there is no multithread and NUMA, so >> + * a CPU is a sibling with itself, and the all possible CPUs >> + * are supposed to belong to the same socket (NUMA node). >> + */ >> cpumask_set_cpu(cpu, per_cpu(cpu_sibling_mask, cpu)); >> - cpumask_set_cpu(cpu, per_cpu(cpu_core_mask, cpu)); >> + cpumask_copy(per_cpu(cpu_core_mask, cpu), &cpu_possible_map); >> >> return 0; >> } >> @@ -277,6 +285,10 @@ void __init smp_init_cpus(void) >> warning_add("WARNING: HMP COMPUTING HAS BEEN ENABLED.\n" >> "It has implications on the security and stability of >> the system,\n" >> "unless the cpu affinity of all domains is >> specified.\n"); >> + >> + if ( system_cpuinfo.mpidr.mt == 1 ) >> + warning_add("WARNING: MULTITHREADING HAS BEEN DETECTED ON THE >> PROCESSOR.\n" >> + "It might impact the security of the system.\n"); >> } >> >> unsigned int __init smp_get_max_cpus(void) > ~Michal
