From: Dave Hansen <dave.hansen@intel.com>
To: Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Andy Lutomirski <luto@kernel.org>,
Josh Poimboeuf <jpoimboe@redhat.com>,
Juergen Gross <jgross@suse.com>,
Peter Zijlstra <peterz@infradead.org>,
Borislav Petkov <bp@alien8.de>, Jiri Kosina <jkosina@suse.cz>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Brian Gerst <brgerst@gmail.com>,
David Laight <David.Laight@aculab.com>,
Denys Vlasenko <dvlasenk@redhat.com>,
Eduardo Valentin <eduval@amazon.com>,
Greg KH <gregkh@linuxfoundation.org>,
Will Deacon <will.deacon@arm.com>,
aliguori@amazon.com, daniel.gruss@iaik.tugraz.at,
hughd@google.com, keescook@google.com,
Andrea Arcangeli <aarcange@redhat.com>,
Waiman Long <llong@redhat.com>, Pavel Machek <pavel@ucw.cz>,
"David H . Gutteridge" <dhgutteridge@sympatico.ca>,
jroedel@suse.de
Subject: Re: [PATCH 2/3] x86/mm/pti: Don't clear permissions in pti_clone_pmd()
Date: Tue, 7 Aug 2018 11:34:46 -0700 [thread overview]
Message-ID: <feea2aff-91ff-89a6-9d7c-5402a1d6a27f@intel.com> (raw)
In-Reply-To: <1533637471-30953-3-git-send-email-joro@8bytes.org>
On 08/07/2018 03:24 AM, Joerg Roedel wrote:
> The function sets the global-bit on cloned PMD entries,
> which only makes sense when the permissions are identical
> between the user and the kernel page-table.
>
> Further, only write-permissions are cleared for entry-text
> and kernel-text sections, which are not writeable anyway.
I think this patch is correct, but I'd be curious if Andy remembers why
we chose to clear _PAGE_RW on these things. It might have been that we
were trying to say that the *entry* code shouldn't write to this stuff,
regardless of whether the normal kernel can.
But, either way, I agree with the logic here that Global pages must
share permissions between both mappings, so feel free to add my Ack. I
just want to make sure Andy doesn't remember some detail I'm forgetting.
next prev parent reply other threads:[~2018-08-07 18:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-07 10:24 [PATCH 0/3] PTI for x86-32 Fixes Joerg Roedel
2018-08-07 10:24 ` [PATCH 1/3] x86/mm/pti: Fix 32 bit PCID check Joerg Roedel
2018-08-07 10:24 ` [PATCH 2/3] x86/mm/pti: Don't clear permissions in pti_clone_pmd() Joerg Roedel
2018-08-07 18:34 ` Dave Hansen [this message]
2018-08-07 19:38 ` Andy Lutomirski
2018-08-07 20:21 ` Thomas Gleixner
2018-08-07 20:28 ` Andy Lutomirski
2018-08-07 10:24 ` [PATCH 3/3] x86/mm/pti: Clone kernel-image on PTE level for 32 bit Joerg Roedel
2018-08-17 2:44 ` [PATCH 0/3] PTI for x86-32 Fixes David H. Gutteridge
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