Messages in this thread Patch in this message | | | Date | Fri, 12 Feb 2021 18:58:53 +0800 | From | Shuo A Liu <> | Subject | Re: [PATCH] virt: acrn: Fix vCPU removing code build error |
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Hi Greg,
On Fri 12.Feb'21 at 8:52:33 +0100, Greg Kroah-Hartman wrote: >On Fri, Feb 12, 2021 at 12:57:24PM +0800, shuo.a.liu@intel.com wrote: >> From: Shuo Liu <shuo.a.liu@intel.com> >> >> vCPU removing code depends on CONFIG_HOTPLUG_CPU as it uses remove_cpu() >> and add_cpu(). Make the vCPU removing interface building with >> CONFIG_HOTPLUG_CPU. >> >> ../drivers/virt/acrn/hsm.c: In function ‘remove_cpu_store’: >> ../drivers/virt/acrn/hsm.c:389:3: error: implicit declaration of function ‘remove_cpu’; [-Werror=implicit-function-declaration] >> remove_cpu(cpu); >> >> ../drivers/virt/acrn/hsm.c:402:2: error: implicit declaration of function ‘add_cpu’; [-Werror=implicit-function-declaration] >> add_cpu(cpu); >> >> Fixes: 279dcf693ac7 ("virt: acrn: Introduce an interface for Service VM to control vCPU") >> Reported-by: Randy Dunlap <rdunlap@infradead.org> >> Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested >> Signed-off-by: Shuo Liu <shuo.a.liu@intel.com> >> --- >> drivers/virt/acrn/hsm.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/drivers/virt/acrn/hsm.c b/drivers/virt/acrn/hsm.c >> index 1f6b7c54a1a4..e340788aacdf 100644 >> --- a/drivers/virt/acrn/hsm.c >> +++ b/drivers/virt/acrn/hsm.c >> @@ -372,6 +372,7 @@ static int acrn_dev_release(struct inode *inode, struct file *filp) >> return 0; >> } >> >> +#ifdef CONFIG_HOTPLUG_CPU >> static ssize_t remove_cpu_store(struct device *dev, >> struct device_attribute *attr, >> const char *buf, size_t count) >> @@ -403,9 +404,12 @@ static ssize_t remove_cpu_store(struct device *dev, >> return ret; >> } >> static DEVICE_ATTR_WO(remove_cpu); >> +#endif >> >> static struct attribute *acrn_attrs[] = { >> +#ifdef CONFIG_HOTPLUG_CPU >> &dev_attr_remove_cpu.attr, >> +#endif >> NULL >> }; >> >> > >Shouldn't the real solution for this be that remove_cpu() and add_cpu() >have function prototypes for when this is not enabled in the kernel >build?
Something like this in linux/cpu.h?
diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 3aaa0687e8df..94a578a96202 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -108,6 +108,8 @@ static inline void cpu_maps_update_done(void) { }
+static inline int add_cpu(unsigned int cpu) { return 0;} + #endif /* CONFIG_SMP */ extern struct bus_type cpu_subsys;
@@ -137,6 +139,7 @@ static inline int cpus_read_trylock(void) { return true; } static inline void lockdep_assert_cpus_held(void) { } static inline void cpu_hotplug_disable(void) { } static inline void cpu_hotplug_enable(void) { } +static inline int remove_cpu(unsigned int cpu) { return -EPERM; } static inline void smp_shutdown_nonboot_cpus(unsigned int primary_cpu) { } #endif /* !CONFIG_HOTPLUG_CPU */
> >Putting #ifdef in .c files like this is not a good idea at all. > >Then, at runtime, you can determine if you need to create this sysfs >file or not, as you do not want to expose it to userspace if the kernel >can not handle it, right?
Right. I don't want to expose the sysfs to userspace if the kernel built w/o CONFIG_HOTPLUG_CPU. But how to implement that if #ifdef is not used? misc_register() creates sysfs with .groups (acrn_attr_groups) unconditionally, then userspace can see the interface even it doesn't work.
Thanks shuo
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