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From: Dave Hansen <dave.hansen@intel.com>
To: Mike Kravetz <mike.kravetz@oracle.com>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org,
	linux-s390@vger.kernel.org, sparclinux@vger.kernel.org,
	linux-doc@vger.kernel.org
Cc: Albert Ou <aou@eecs.berkeley.edu>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	"Shutemov, Kirill" <kirill.shutemov@intel.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Ingo Molnar <mingo@redhat.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Paul Mackerras <paulus@samba.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Longpeng <longpeng2@huawei.com>, Will Deacon <will@kernel.org>,
	"David S.Miller" <davem@davemloft.net>
Subject: Re: [PATCH 1/4] hugetlbfs: add arch_hugetlb_valid_size
Date: Thu, 26 Mar 2020 16:10:56 -0700
Message-ID: <ae80063f-cef8-3141-3c6b-9130def5396a@intel.com> (raw)
In-Reply-To: <530e6e11-ad1a-55bc-e61e-9da6eb7fea21@oracle.com>

On 3/26/20 2:56 PM, Mike Kravetz wrote:
> Perhaps it would be best to check hugepages_supported() when parsing
> hugetlb command line options.  If not enabled, throw an error.  This
> will be much easier to do after moving all command line parsing to
> arch independent code.

Yeah, that sounds sane.

> Is that a sufficient way to address this concern?  I think it is a good
> change in any case.

(Thanks to Kirill for pointing this out.)

So, it turns out the x86 huge page enumeration is totally buggered.
X86_FEATURE_PSE is actually meaningless on 64-bit (and 32-bit PAE).  All
CPUs architecturally support 2MB pages regardless of X86_FEATURE_PSE and
the state of CR4.PSE.

So, on x86_64 at least, hugepages_supported() should *always* return 1.

1GB page support can continue to be dependent on X86_FEATURE_GBPAGES.


  reply index

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-18 22:06 [PATCH 0/4] Clean up hugetlb boot command line processing Mike Kravetz
2020-03-18 22:06 ` [PATCH 1/4] hugetlbfs: add arch_hugetlb_valid_size Mike Kravetz
2020-03-18 22:09   ` Will Deacon
2020-03-18 22:38     ` Mike Kravetz
2020-03-18 22:15   ` Dave Hansen
2020-03-18 22:52     ` Mike Kravetz
2020-03-18 23:36       ` Dave Hansen
2020-03-26 21:56         ` Mike Kravetz
2020-03-26 23:10           ` Dave Hansen [this message]
2020-03-25  2:58       ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2020-03-25  9:38         ` Christian Borntraeger
2020-03-19  0:48   ` kbuild test robot
2020-03-19  1:39   ` kbuild test robot
2020-03-19  7:00   ` Christophe Leroy
2020-03-19 18:17     ` Mike Kravetz
2020-03-23 23:43   ` Mina Almasry
2020-03-18 22:06 ` [PATCH 2/4] hugetlbfs: move hugepagesz= parsing to arch independent code Mike Kravetz
2020-03-19  7:04   ` Christophe Leroy
2020-03-19 17:00     ` Mike Kravetz
2020-03-23 23:56     ` Mina Almasry
2020-03-18 22:06 ` [PATCH 3/4] hugetlbfs: remove hugetlb_add_hstate() warning for existing hstate Mike Kravetz
2020-03-24  0:01   ` Mina Almasry
2020-03-24  0:16     ` Mike Kravetz
2020-03-24  0:23       ` Mina Almasry
2020-03-18 22:06 ` [PATCH 4/4] hugetlbfs: clean up command line processing Mike Kravetz
2020-03-19  0:20   ` Randy Dunlap
2020-03-19  2:42     ` Mike Kravetz
2020-03-24  0:43   ` Mina Almasry
2020-03-24  3:47     ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2020-03-25  1:12       ` Mike Kravetz

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