linux-kernel - Re: [PATCH v4 1/2] x86/setup: always add the beginning of RAM as memblock.memory

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20210201145534.GA9009@MiWiFi-R3L-srv>
Date:   Mon, 1 Feb 2021 22:55:34 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Łukasz Majczak <lma@...ihalf.com>,
        Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...nel.org>,
        Mike Rapoport <rppt@...ux.ibm.com>, Qian Cai <cai@....pw>,
        "Sarvela, Tomi P" <tomi.p.sarvela@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, stable@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH v4 1/2] x86/setup: always add the beginning of RAM as
 memblock.memory

On 02/01/21 at 04:34pm, Mike Rapoport wrote:
> On Mon, Feb 01, 2021 at 07:26:05PM +0800, Baoquan He wrote:
> > On 02/01/21 at 10:32am, David Hildenbrand wrote:
> > > 
> > > 2) In init_zone_unavailable_mem(), similar to round_up(max_pfn,
> > > PAGES_PER_SECTION) handling, consider range
> > > 	[round_down(min_pfn, PAGES_PER_SECTION), min_pfn - 1]
> > > which would handle in the x86-64 case [0..0] and, therefore, initialize PFN
> > > 0.
> > 
> > Sounds reasonable. Maybe we can change to get the real expected lowest
> > pfn from find_min_pfn_for_node() by iterating memblock.memory and
> > memblock.reserved and comparing.
> 
> As I've found out the hard way [1], reserved memory is not necessary present.
> 
> There could be a system that instead of reserving memory at 0xfe000000 like
> in Guillaume's report, could have it reserved at 0x0 and populated only
> from the first gigabyte...

OK. I thought that we can even compare memblock.memory.regions[0].base
with memblock.reserved.regions[0].base and take the smaller one as the
lowest pfn and assign it to arch_zone_lowest_possible_pfn[0]. When we
try to get the present pages, we still check memblock.memory with
for_each_mem_pfn_range(). Since we will consider and take reserved
memory into zone anyway, arch_zone_lowest_possible_pfn[] only impact the
boundary of zone. Just rough thought, please ignore it if something is
missed.

Thanks
Baoquan