Re: [PATCH v6 3/4] x86/vmemmap: Handle unpopulated sub-pmd ranges

From: Oscar Salvador <osalvador@suse.de>
To: Dave Hansen <dave.hansen@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	David Hildenbrand <david@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>,
	Michal Hocko <mhocko@kernel.org>, Zi Yan <ziy@nvidia.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v6 3/4] x86/vmemmap: Handle unpopulated sub-pmd ranges
Date: Thu, 11 Mar 2021 22:48:34 +0100	[thread overview]
Message-ID: <YEqQMm6+oQiQmwB0@localhost.localdomain> (raw)
In-Reply-To: <0c4132aa-5d59-c0ba-5cfc-4ac401feba04@intel.com>

On Thu, Mar 11, 2021 at 01:29:39PM -0800, Dave Hansen wrote:
> On 3/9/21 1:40 PM, Oscar Salvador wrote:
> > +static void __meminit vmemmap_use_new_sub_pmd(unsigned long start, unsigned long end)
> > +{
> > +	/*
> > +	 * Could be our memmap page is filled with PAGE_UNUSED already from a
> > +	 * previous remove. Make sure to reset it.
> > +	 */
> > +	vmemmap_use_sub_pmd(start);
> > +
> > +	/*
> > +	 * Mark with PAGE_UNUSED the unused parts of the new memmap range
> > +	 */
> > +	if (!IS_ALIGNED(start, PMD_SIZE))
> > +		memset((void *)start, PAGE_UNUSED,
> > +		        start - ALIGN_DOWN(start, PMD_SIZE));
> > +	if (!IS_ALIGNED(end, PMD_SIZE))
> > +		memset((void *)end, PAGE_UNUSED,
> > +		        ALIGN(end, PMD_SIZE) - end);
> > +}
> > +#endif
> 
> This is apparently under both CONFIG_SPARSEMEM_VMEMMAP and
> CONFIG_MEMORY_HOTPLUG #ifdefs.  It errors out at compile-time with this
> config: https://sr71.net/~dave/intel/config-mmotm-20210311

It seems that mmotm still has v5.
v6 (this one) fixed that up. I basically moved the code out of
MEMORY_HOTPLUG #ifdefs.

I could not reproduce your error on v6.

-- 
Oscar Salvador
SUSE L3