From: Baoquan He <bhe@redhat.com>
To: Mike Travis <mike.travis@hpe.com>
Cc: Ingo Molnar <mingo@kernel.org>,
rja@hpe.com, frank.ramsay@hpe.com, linux-kernel@vger.kernel.org,
x86@kernel.org, mingo@redhat.com, tglx@linutronix.de,
hpa@zytor.com, thgarnie@google.com, keescook@chromium.org,
akpm@linux-foundation.org, yamada.masahiro@socionext.com,
sivanich@hpe.com
Subject: Re: [PATCH v2 RESEND 2/2] x86/mm/KASLR: Do not adapt the size of the direct mapping section for SGI UV system
Date: Sat, 30 Sep 2017 19:25:04 +0800 [thread overview]
Message-ID: <20170930112504.GE17588@x1> (raw)
In-Reply-To: <25fc5345-3273-447e-de6a-2ac7c56d0f00@hpe.com>
Hi Mike,
On 09/28/17 at 07:10am, Mike Travis wrote:
>
>
> On 9/28/2017 2:01 AM, Ingo Molnar wrote:
> >
> > > If on SGI UV system, the kaslr_regions[0].size_tb, namely the size of
> > > the direct mapping section, is incorrect.
> > >
> > > Its direct mapping size includes two parts:
> > > #1 RAM size of system
> > > #2 MMIOH region size which only SGI UV system has.
> > >
> > > However, the #2 can only be got till uv_system_init() is called in
> > > native_smp_prepare_cpus(). That is too late for mm KASLR calculation.
> > > That's why I made this hack.
> > >
> > > I checked uv_system_init() code, seems not easy to know the size of
> > > MMIOH region before or inside kernel_randomize_memory(). I have CCed UV
> > > devel experts, not sure if they have any idea about this. Otherwise,
> > > this patch could be the only way I can think of.
> > >
> > > Hi Mike and Russ,
> > >
> > > Is there any chance we can get the size of MMIOH region before mm KASLR
> > > code, namely before we call kernel_randomize_memory()?
>
> The sizes of the MMIOL and MMIOH areas are tied into the HUB design and how
> it is communicated to BIOS and the kernel. This is via some of the config
> MMR's found in the HUB and it would be impossible to provide any access to
> these registers as they change with each new UV architecture.
>
> The kernel does reserve the memory in the EFI memmap. I can send you a
> console log of the full startup that includes the MMIOH reservations. Note
> that it is dependent on what I/O devices are actually present as UV does not
> map empty slots unless forced (because we'd quickly run out of resources.)
> Also, the EFI memmap entries do not specify the exact usage of the contained
> areas.
Does that mean we can get the size of MMIOH from efi entries? If yes,
please help provide a console log including those. If can get size from
efi, it will be more acceptable.
Or I can ask Frank to loan his uv system to me, not sure if he is doing
testing with them.
Thanks
Baoquan
>
> >
> > I don't mind system specific quirks to hardware enumeration details, as long as
> > they don't pollute generic code with such special hacks.
> >
> > I.e. in this case it's wrong to allow kaslr_regions[0].size_tb to be wrong. Any
> > other code that relies on it in the future will be wrong as well on UV systems.
>
> Which may come into play on other arches with the new upcoming memory
> technologies.
> >
> > The right quirk would be to fix that up where it gets introduced, or something
> > like that.
>
> Yes, does make sense.
> >
> > Thanks,
> >
> > Ingo
> >
next prev parent reply other threads:[~2017-09-30 11:25 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-07 7:42 [PATCH v2 RESEND 0/2] x86/mm/KASLR: Do not adapt the size of the direct mapping section for SGI UV system Baoquan He
2017-09-07 7:42 ` [PATCH v2 RESEND 1/2] x86/UV: Introduce a helper function to check UV system at earlier stage Baoquan He
2017-09-14 7:29 ` Baoquan He
2017-09-14 7:49 ` Dave Young
2017-09-14 8:08 ` Baoquan He
2017-09-15 0:47 ` Dave Young
2017-09-15 0:55 ` Dave Young
2017-09-07 7:42 ` [PATCH v2 RESEND 2/2] x86/mm/KASLR: Do not adapt the size of the direct mapping section for SGI UV system Baoquan He
2017-09-28 7:56 ` Ingo Molnar
2017-09-28 8:31 ` Baoquan He
2017-09-28 9:01 ` Ingo Molnar
2017-09-28 14:10 ` Mike Travis
2017-09-30 11:25 ` Baoquan He [this message]
2018-05-17 3:18 ` Baoquan He
2018-05-17 15:06 ` Ramsay, Frank
2018-05-17 15:47 ` Mike Travis
[not found] ` <53301a1e-e817-912f-cf7d-0000b078c7a3@hpe.com>
[not found] ` <20180523000306.GY24627@MiWiFi-R3L-srv>
[not found] ` <7ce3cc80-3991-f914-c539-9fa38256ea4b@hpe.com>
2018-05-31 3:26 ` Baoquan He
2017-09-14 1:44 ` [PATCH v2 RESEND 0/2] " Baoquan He
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