Subject: Re: [PATCH 3/3] memblock: cleanup memblock_free interface

From: Mike Rapoport <[email-masked]>
Date: Fri, 24 Sep 2021 08:32:21 +0300

On Thu, Sep 23, 2021 at 03:54:46PM +0200, Christophe Leroy wrote:
> 
> Le 23/09/2021 à 14:01, Mike Rapoport a écrit :
> > On Thu, Sep 23, 2021 at 11:47:48AM +0200, Christophe Leroy wrote:
> > > 
> > > 
> > > Le 23/09/2021 à 09:43, Mike Rapoport a écrit :
> > > > From: Mike Rapoport <[email-masked]>
> > > > 
> > > > For ages memblock_free() interface dealt with physical addresses even
> > > > despite the existence of memblock_alloc_xx() functions that return a
> > > > virtual pointer.
> > > > 
> > > > Introduce memblock_phys_free() for freeing physical ranges and repurpose
> > > > memblock_free() to free virtual pointers to make the following pairing
> > > > abundantly clear:
> > > > 
> > > > 	int memblock_phys_free(phys_addr_t base, phys_addr_t size);
> > > > 	phys_addr_t memblock_phys_alloc(phys_addr_t base, phys_addr_t size);
> > > > 
> > > > 	void *memblock_alloc(phys_addr_t size, phys_addr_t align);
> > > > 	void memblock_free(void *ptr, size_t size);
> > > > 
> > > > Replace intermediate memblock_free_ptr() with memblock_free() and drop
> > > > unnecessary aliases memblock_free_early() and memblock_free_early_nid().
> > > > 
> > > > Suggested-by: Linus Torvalds <[email-masked]>
> > > > Signed-off-by: Mike Rapoport <[email-masked]>
> > > > ---
> > > 
> > > > diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
> > > > index 1a04e5bdf655..37826d8c4f74 100644
> > > > --- a/arch/s390/kernel/smp.c
> > > > +++ b/arch/s390/kernel/smp.c
> > > > @@ -723,7 +723,7 @@ void __init smp_save_dump_cpus(void)
> > > >    			/* Get the CPU registers */
> > > >    			smp_save_cpu_regs(sa, addr, is_boot_cpu, page);
> > > >    	}
> > > > -	memblock_free(page, PAGE_SIZE);
> > > > +	memblock_phys_free(page, PAGE_SIZE);
> > > >    	diag_amode31_ops.diag308_reset();
> > > >    	pcpu_set_smt(0);
> > > >    }
> > > > @@ -880,7 +880,7 @@ void __init smp_detect_cpus(void)
> > > >    	/* Add CPUs present at boot */
> > > >    	__smp_rescan_cpus(info, true);
> > > > -	memblock_free_early((unsigned long)info, sizeof(*info));
> > > > +	memblock_free(info, sizeof(*info));
> > > >    }
> > > >    /*
> > > 
> > > I'm a bit lost. IIUC memblock_free_early() and memblock_free() where
> > > identical.
> > 
> > Yes, they were, but all calls to memblock_free_early() were using
> > __pa(vaddr) because they had a virtual address at hand.
> 
> I'm still not following. In the above memblock_free_early() was taking
> (unsigned long)info . Was it a bug ? 

Not really because s390 has pa == va:

https://elixir.bootlin.com/linux/latest/source/arch/s390/include/asm/page.h#L169

-- 
Sincerely yours,
Mike.