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Re: [PATCH v8 04/15] xen/sysctl: Nest cpufreq scaling options

Date: Wed, 23 Aug 2023 15:16:06 +0200

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Cc: Wei Liu <wl@xxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx

Delivery-date: Wed, 23 Aug 2023 13:16:33 +0000

List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 07.08.2023 20:51, Jason Andryuk wrote: > --- a/tools/libs/ctrl/xc_pm.c > +++ b/tools/libs/ctrl/xc_pm.c > @@ -245,6 +245,45 @@ int xc_get_cpufreq_para(xc_interface *xch, int cpuid, > sys_para->freq_num = user_para->freq_num; > sys_para->gov_num = user_para->gov_num; > > + /* Sanity check struct layout */ > + BUILD_BUG_ON(sizeof(*user_para) != sizeof(*sys_para)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), cpu_num) != > + offsetof(typeof(*sys_para), cpu_num)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), freq_num) != > + offsetof(typeof(*sys_para), freq_num)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), gov_num) != > + offsetof(typeof(*sys_para), gov_num)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), affected_cpus) != > + offsetof(typeof(*sys_para), affected_cpus)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), scaling_available_frequencies) > != > + offsetof(typeof(*sys_para), > scaling_available_frequencies)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), scaling_available_governors) != > + offsetof(typeof(*sys_para), scaling_available_governors)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), scaling_driver) != > + offsetof(typeof(*sys_para), scaling_driver)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), cpuinfo_cur_freq) != > + offsetof(typeof(*sys_para), cpuinfo_cur_freq)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), cpuinfo_max_freq) != > + offsetof(typeof(*sys_para), cpuinfo_max_freq)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), cpuinfo_min_freq) != > + offsetof(typeof(*sys_para), cpuinfo_min_freq)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), u.s.scaling_cur_freq) != > + offsetof(typeof(*sys_para), u.s.scaling_cur_freq)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), u.s.scaling_governor) != > + offsetof(typeof(*sys_para), u.s.scaling_governor)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), u.s.scaling_max_freq) != > + offsetof(typeof(*sys_para), u.s.scaling_max_freq)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), u.s.scaling_min_freq) != > + offsetof(typeof(*sys_para), u.s.scaling_min_freq)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), u.s.u.userspace) != > + offsetof(typeof(*sys_para), u.s.u.userspace)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), u.s.u.ondemand) != > + offsetof(typeof(*sys_para), u.s.u.ondemand)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), u.cppc_para) != > + offsetof(typeof(*sys_para), u.cppc_para)); > + BUILD_BUG_ON(offsetof(typeof(*user_para), turbo_enabled) != > + offsetof(typeof(*sys_para), turbo_enabled)); As the build breakage shows, these checks are too aggressive. The two layouts can't possibly be the same with 32-bit tool stacks (and hence pointers being 32 bits wide). But we also don't need all these checks; what may need checking is only what subsequently is subject to memcpy(), not anything that's dealt with by field-wise copying. Jan

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