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From: Thomas Gleixner <tglx@linutronix.de>
To: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
	pbonzini@redhat.com, rkrcmar@redhat.com, mingo@redhat.com,
	bp@alien8.de, hpa@zytor.com, dave.hansen@linux.intel.com,
	luto@kernel.org, peterz@infradead.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
Subject: Re: [RFC v2 00/27] Kernel Address Space Isolation
Date: Fri, 12 Jul 2019 17:23:44 +0200 (CEST)
Message-ID: <alpine.DEB.2.21.1907121719290.1788@nanos.tec.linutronix.de> (raw)
In-Reply-To: <bfd62213-c7c0-4a90-b377-0de7d9557c4c@oracle.com>

On Fri, 12 Jul 2019, Alexandre Chartre wrote:
> On 7/12/19 3:51 PM, Dave Hansen wrote:
> > BTW, the PTI CR3 writes are not *strictly* about the interrupt coming
> > from user vs. kernel.  It's tricky because there's a window both in the
> > entry and exit code where you are in the kernel but have a userspace CR3
> > value.  You end up needing a CR3 write when you have a userspace CR3
> > value when the interrupt occurred, not only when you interrupt userspace
> > itself.
> > 
> 
> Right. ASI is simpler because it comes from the kernel and return to the
> kernel. There's just a small window (on entry) where we have the ASI CR3
> but we quickly switch to the full kernel CR3.

That's wrong in several aspects.

   1) You are looking at it purely from the VMM perspective, which is bogus
      as you already said, that this can/should be used to be extended to
      other scenarios (including kvm ioctl or such).

      So no, it's not just coming from kernel space and returning to it.

      If that'd be true then the entry code could just stay as is because
      you can handle _ALL_ of that very trivial in the atomic VMM
      enter/exit code.

   2) It does not matter how small that window is. If there is a window
      then this needs to be covered, no matter what.

Thanks,

	tglx

  reply index

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-11 14:25 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 [this message]
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
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

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