Re: [PATCH v2 2/3] vmcore: allow fadump to export vmcore even if is_kdump_kernel() is false

[Hari Bathini]

On 11/09/23 4:01 pm, Baoquan He wrote:
> On 09/11/23 at 05:13pm, Michael Ellerman wrote:
> > Hari Bathini <hbathini@xxxxxxxxxxxxx> writes:
> > > Currently, is_kdump_kernel() returns true when elfcorehdr_addr is set.
> > > While elfcorehdr_addr is set for kexec based kernel dump mechanism,
> > > alternate dump capturing methods like fadump [1] also set it to export
> > > the vmcore. Since, is_kdump_kernel() is used to restrict resources in
> > > crash dump capture kernel and such restrictions are not desirable for
> > > fadump, allow is_kdump_kernel() to be defined differently for fadump
> > > case. With that change, include is_fadump_active() check in functions
> > > is_vmcore_usable() & vmcore_unusable() to be able to export vmcore for
> > > fadump case too.
> > ...
> > > diff --git a/include/linux/crash_dump.h b/include/linux/crash_dump.h
> > > index 0f3a656293b0..de8a9fabfb6f 100644
> > > --- a/include/linux/crash_dump.h
> > > +++ b/include/linux/crash_dump.h
> > > @@ -50,6 +50,7 @@ void vmcore_cleanup(void);
> > >   #define vmcore_elf64_check_arch(x) (elf_check_arch(x) || vmcore_elf_check_arch_cross(x))
> > >   #endif
> > >   
> > > +#ifndef is_kdump_kernel
> > >   /*
> > >    * is_kdump_kernel() checks whether this kernel is booting after a panic of
> > >    * previous kernel or not. This is determined by checking if previous kernel
> > > @@ -64,6 +65,19 @@ static inline bool is_kdump_kernel(void)
> > >   {
> > >   	return elfcorehdr_addr != ELFCORE_ADDR_MAX;
> > >   }
> > > +#endif
> > > +
> > > +#ifndef is_fadump_active
> > > +/*
> > > + * If f/w assisted dump capturing mechanism (fadump), instead of kexec based
> > > + * dump capturing mechanism (kdump) is exporting the vmcore, then this function
> > > + * will be defined in arch specific code to return true, when appropriate.
> > > + */
> > > +static inline bool is_fadump_active(void)
> > > +{
> > > +	return false;
> > > +}
> > > +#endif
> > >   
> > >   /* is_vmcore_usable() checks if the kernel is booting after a panic and
> > >    * the vmcore region is usable.
> > > @@ -75,7 +89,8 @@ static inline bool is_kdump_kernel(void)
> > >   
> > >   static inline int is_vmcore_usable(void)
> > >   {
> > > -	return is_kdump_kernel() && elfcorehdr_addr != ELFCORE_ADDR_ERR ? 1 : 0;
> > > +	return (is_kdump_kernel() || is_fadump_active())
> > > +		&& elfcorehdr_addr != ELFCORE_ADDR_ERR ? 1 : 0;
> > >   }
> > >   
> > >   /* vmcore_unusable() marks the vmcore as unusable,
> > > @@ -84,7 +99,7 @@ static inline int is_vmcore_usable(void)
> > >   
> > >   static inline void vmcore_unusable(void)
> > >   {
> > > -	if (is_kdump_kernel())
> > > +	if (is_kdump_kernel() || is_fadump_active())
> > >   		elfcorehdr_addr = ELFCORE_ADDR_ERR;
> > >   }
> >
> > I think it would be cleaner to decouple is_vmcore_usable() and
> > vmcore_usable() from is_kdump_kernel().
> >
> > ie, make them operate solely based on the value of elforehdr_addr:
> >
> > static inline int is_vmcore_usable(void)
> > {
> > 	elfcorehdr_addr != ELFCORE_ADDR_ERR && \
> > 		elfcorehdr_addr != ELFCORE_ADDR_MAX;
>
> Agree. I fell into the blind corner of thinking earlier. Above change
> is better.

Thanks for the reviews.
Posted v3.

- Hari