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From: Dave Hansen <dave.hansen@intel.com>
To: Peter Zijlstra <peterz@infradead.org>,
	Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	pbonzini@redhat.com, rkrcmar@redhat.com, mingo@redhat.com,
	bp@alien8.de, hpa@zytor.com, dave.hansen@linux.intel.com,
	luto@kernel.org, kvm@vger.kernel.org, x86@kernel.org,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	konrad.wilk@oracle.com, jan.setjeeilers@oracle.com,
	liran.alon@oracle.com, jwadams@google.com, graf@amazon.de,
	rppt@linux.vnet.ibm.com, Paul Turner <pjt@google.com>
Subject: Re: [RFC v2 00/27] Kernel Address Space Isolation
Date: Fri, 12 Jul 2019 06:54:22 -0700	[thread overview]
Message-ID: <3626998c-509f-b434-1f66-9db2c09c47d4@intel.com> (raw)
In-Reply-To: <20190712125059.GP3419@hirez.programming.kicks-ass.net>

On 7/12/19 5:50 AM, Peter Zijlstra wrote:
> PTI is not mapping         kernel space to avoid             speculation crap (meltdown).
> ASI is not mapping part of kernel space to avoid (different) speculation crap (MDS).
> 
> See how very similar they are?

That's an interesting point.

I'd add that PTI maps a part of kernel space that partially overlaps
with what ASI wants.

> But looking at it that way, it makes no sense to retain 3 address
> spaces, namely:
> 
>   user / kernel exposed / kernel private.
> 
> Specifically, it makes no sense to expose part of the kernel through MDS
> but not through Meltdown. Therefore we can merge the user and kernel
> exposed address spaces.
> 
> And then we've fully replaced PTI.

So, in one address space (PTI/user or ASI), we say, "screw it" and all
the data mapped is exposed to speculation attacks.  We have to be very
careful about what we map and expose here.

The other (full kernel) address space we are more careful about what we
*do* instead of what we map.  We map everything but have to add
mitigations to ensure that we don't leak anything back to the exposed
address space.

So, maybe we're not replacing PTI as much as we're growing PTI so that
we can run more kernel code with the (now inappropriately named) user
page tables.


  parent reply	other threads:[~2019-07-12 13:54 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-11 14:25 [RFC v2 00/27] Kernel Address Space Isolation Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 01/26] mm/x86: Introduce kernel address space isolation Alexandre Chartre
2019-07-11 21:33   ` Thomas Gleixner
2019-07-12  7:43     ` Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 02/26] mm/asi: Abort isolation on interrupt, exception and context switch Alexandre Chartre
2019-07-11 20:11   ` Andi Kleen
2019-07-11 20:17     ` Mike Rapoport
2019-07-11 20:41       ` Alexandre Chartre
2019-07-12  0:05   ` Andy Lutomirski
2019-07-12  7:50     ` Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 03/26] mm/asi: Handle page fault due to address space isolation Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 04/26] mm/asi: Functions to track buffers allocated for an ASI page-table Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 05/26] mm/asi: Add ASI page-table entry offset functions Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 06/26] mm/asi: Add ASI page-table entry allocation functions Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 07/26] mm/asi: Add ASI page-table entry set functions Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 08/26] mm/asi: Functions to populate an ASI page-table from a VA range Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 09/26] mm/asi: Helper functions to map module into ASI Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 10/26] mm/asi: Keep track of VA ranges mapped in ASI page-table Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 11/26] mm/asi: Functions to clear ASI page-table entries for a VA range Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 12/26] mm/asi: Function to copy page-table entries for percpu buffer Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 13/26] mm/asi: Add asi_remap() function Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 14/26] mm/asi: Handle ASI mapped range leaks and overlaps Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 15/26] mm/asi: Initialize the ASI page-table with core mappings Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 16/26] mm/asi: Option to map current task into ASI Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 17/26] rcu: Move tree.h static forward declarations to tree.c Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 18/26] rcu: Make percpu rcu_data non-static Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 19/26] mm/asi: Add option to map RCU data Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 20/26] mm/asi: Add option to map cpu_hw_events Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 21/26] mm/asi: Make functions to read cr3/cr4 ASI aware Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 22/26] KVM: x86/asi: Introduce address_space_isolation module parameter Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 23/26] KVM: x86/asi: Introduce KVM address space isolation Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 24/26] KVM: x86/asi: Populate the KVM ASI page-table Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 25/26] KVM: x86/asi: Switch to KVM address space on entry to guest Alexandre Chartre
2019-07-11 14:25 ` [RFC v2 26/26] KVM: x86/asi: Map KVM memslots and IO buses into KVM ASI Alexandre Chartre
2019-07-11 14:40 ` [RFC v2 00/27] Kernel Address Space Isolation Alexandre Chartre
2019-07-11 22:38 ` Dave Hansen
2019-07-12  8:09   ` Alexandre Chartre
2019-07-12 13:51     ` Dave Hansen
2019-07-12 14:06       ` Alexandre Chartre
2019-07-12 15:23         ` Thomas Gleixner
2019-07-12 10:44   ` Thomas Gleixner
2019-07-12 11:56     ` Alexandre Chartre
2019-07-12 12:50       ` Peter Zijlstra
2019-07-12 13:43         ` Alexandre Chartre
2019-07-12 13:58           ` Dave Hansen
2019-07-12 14:36           ` Andy Lutomirski
2019-07-14 18:17             ` Alexander Graf
2019-07-12 13:54         ` Dave Hansen [this message]
2019-07-12 15:20           ` Peter Zijlstra
2019-07-12 15:16         ` Thomas Gleixner
2019-07-12 16:37           ` Alexandre Chartre
2019-07-12 16:45             ` Andy Lutomirski
2019-07-14 17:11               ` Mike Rapoport
2019-07-12 19:06             ` Peter Zijlstra
2019-07-14 15:06               ` Andy Lutomirski
2019-07-15 10:33                 ` Peter Zijlstra
2019-07-12 19:48             ` Thomas Gleixner
2019-07-15  8:23               ` Alexandre Chartre
2019-07-15  8:28                 ` Thomas Gleixner
2019-07-12 16:00       ` Thomas Gleixner
2019-07-12 11:44 ` Peter Zijlstra
2019-07-12 12:17   ` Alexandre Chartre
2019-07-12 12:36     ` Peter Zijlstra
2019-07-12 12:47       ` Alexandre Chartre
2019-07-12 13:07         ` Peter Zijlstra
2019-07-12 13:46           ` Alexandre Chartre
2019-07-31 16:31             ` Dario Faggioli
2019-08-22 12:31               ` Alexandre Chartre
2020-07-01 13:55 hackapple
2020-07-01 14:00 黄金海
2020-07-01 14:02 黄金海

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