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From: Baoquan He <bhe@redhat.com>
To: tglx@linutronix.de, stable@vger.kernel.org, mingo@kernel.org,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	peterz@infradead.org, keescook@chromium.org, bp@suse.de,
	luto@kernel.org, hpa@zytor.com, kirill@linux.intel.com,
	dave.hansen@linux.intel.com
Cc: linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/urgent] x86/mm/KASLR: Compute the size of the vmemmap section properly
Date: Sat, 8 Jun 2019 10:14:04 +0800	[thread overview]
Message-ID: <20190608021404.GA26148@MiWiFi-R3L-srv> (raw)
In-Reply-To: <tip-00e5a2bbcc31d5fea853f8daeba0f06c1c88c3ff@git.kernel.org>

On 06/07/19 at 02:16pm, tip-bot for Baoquan He wrote:
> Commit-ID:  00e5a2bbcc31d5fea853f8daeba0f06c1c88c3ff
> Gitweb:     https://git.kernel.org/tip/00e5a2bbcc31d5fea853f8daeba0f06c1c88c3ff
> Author:     Baoquan He <bhe@redhat.com>
> AuthorDate: Thu, 23 May 2019 10:57:44 +0800
> Committer:  Borislav Petkov <bp@suse.de>
> CommitDate: Fri, 7 Jun 2019 23:12:13 +0200
> 
> x86/mm/KASLR: Compute the size of the vmemmap section properly
> 
> The size of the vmemmap section is hardcoded to 1 TB to support the
> maximum amount of system RAM in 4-level paging mode - 64 TB.
> 
> However, 1 TB is not enough for vmemmap in 5-level paging mode. Assuming
> the size of struct page is 64 Bytes, to support 4 PB system RAM in 5-level,
> 64 TB of vmemmap area is needed:
> 
>   4 * 1000^5 PB / 4096 bytes page size * 64 bytes per page struct / 1000^4 TB = 62.5 TB.

Thanks for picking this, Boris.

Here, 4PB = 4*2^50 = 4*1024^5, the vmemmap should be 64 TB, am I right?

> 
> This hardcoding may cause vmemmap to corrupt the following
> cpu_entry_area section, if KASLR puts vmemmap very close to it and the
> actual vmemmap size is bigger than 1 TB.

  reply	other threads:[~2019-06-08  2:14 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-23  2:57 [PATCH v5] x86/mm/KASLR: Fix the size of vmemmap section Baoquan He
     [not found] ` <20190529131454.9818321019@mail.kernel.org>
2019-05-30  0:46   ` Baoquan He
2019-06-07 21:16 ` [tip:x86/urgent] x86/mm/KASLR: Compute the size of the vmemmap section properly tip-bot for Baoquan He
2019-06-08  2:14   ` Baoquan He [this message]
2019-06-08  7:49     ` Borislav Petkov

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