From: Jacob Pan <jacob.jun.pan@linux.intel.com>
To: "Tian, Kevin" <kevin.tian@intel.com>
Cc: "zhangfei.gao@foxmail.com" <zhangfei.gao@foxmail.com>,
"Yu, Fenghua" <fenghua.yu@intel.com>,
"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
"Luck, Tony" <tony.luck@intel.com>,
"Raj, Ashok" <ashok.raj@intel.com>,
jean-philippe <jean-philippe@linaro.org>,
"Peter Zijlstra" <peterz@infradead.org>,
Dave Hansen <dave.hansen@linux.intel.com>, x86 <x86@kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
"Hansen, Dave" <dave.hansen@intel.com>,
iommu <iommu@lists.linux-foundation.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"Lutomirski, Andy" <luto@kernel.org>,
"Poimboe, Josh" <jpoimboe@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
jacob.jun.pan@linux.intel.com
Subject: Re: [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit
Date: Mon, 18 Apr 2022 11:11:35 -0700 [thread overview]
Message-ID: <20220418111135.6260d450@jacob-builder> (raw)
In-Reply-To: <BN9PR11MB52765490BFC5F08CD4F7A9208CF39@BN9PR11MB5276.namprd11.prod.outlook.com>
Hi Kevin,
On Mon, 18 Apr 2022 06:34:19 +0000, "Tian, Kevin" <kevin.tian@intel.com>
wrote:
> > From: Jacob Pan <jacob.jun.pan@linux.intel.com>
> > Sent: Saturday, April 16, 2022 5:00 AM
> >
> > Hi zhangfei.gao@foxmail.com,
> >
> > On Fri, 15 Apr 2022 19:52:03 +0800, "zhangfei.gao@foxmail.com"
> > <zhangfei.gao@foxmail.com> wrote:
> >
> > > >>> A PASID might be still used even though it is freed on mm exit.
> > > >>>
> > > >>> process A:
> > > >>> sva_bind();
> > > >>> ioasid_alloc() = N; // Get PASID N for the mm
> > > >>> fork(): // spawn process B
> > > >>> exit();
> > > >>> ioasid_free(N);
> > > >>>
> > > >>> process B:
> > > >>> device uses PASID N -> failure
> > > >>> sva_unbind();
> > > >>>
> > > >>> Dave Hansen suggests to take a refcount on the mm whenever
> > > >>> binding
> > the
> > > >>> PASID to a device and drop the refcount on unbinding. The mm
> > > >>> won't
> > be
> > > >>> dropped if the PASID is still bound to it.
> > > >>>
> > > >>> Fixes: 701fac40384f ("iommu/sva: Assign a PASID to mm on PASID
> > > >>> allocation and free it on mm exit")
> > > >>>
> > Is process A's mm intended to be used by process B? Or you really should
> > use PASID N on process B's mm? If the latter, it may work for a while
> > until B changes mapping.
> >
> > It seems you are just extending the life of a defunct mm?
> >
>
> IMHO the intention is not to allow B to access A's mm.
>
> The problem is that PASID N is released on exit() of A and then
> reallocated to B before iommu driver gets the chance to quiesce
> the device and clear the PASID entry. According to the discussion
> the quiesce operation must be done when driver calls unbind()
> instead of in mm exit. In this case a failure is reported when
> B tries to call bind() on PASID N due to an already-present entry.
>
> Dave's patch extending the life of A's mm until unbind() is called.
> With it B either gets a different PASID before A's unbind() is
> completed or same PASID N pointing to B's mm after A's unbind().
>
As long as B gets a different PASID, that is fine. It seems PASID N has no
use then.
> Thanks
> Kevin
Thanks,
Jacob
next prev parent reply other threads:[~2022-04-18 18:08 UTC|newest]
Thread overview: 113+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-07 23:02 [PATCH v4 00/11] Re-enable ENQCMD and PASID MSR Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 01/11] iommu/sva: Rename CONFIG_IOMMU_SVA_LIB to CONFIG_IOMMU_SVA Fenghua Yu
2022-02-08 2:39 ` Lu Baolu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 02/11] mm: Change CONFIG option for mm->pasid field Fenghua Yu
2022-02-08 2:40 ` Lu Baolu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 03/11] iommu/ioasid: Introduce a helper to check for valid PASIDs Fenghua Yu
2022-02-08 2:40 ` Lu Baolu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 04/11] kernel/fork: Initialize mm's PASID Fenghua Yu
2022-02-14 17:23 ` Thomas Gleixner
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 05/11] iommu/sva: Assign a PASID to mm on PASID allocation and free it on mm exit Fenghua Yu
2022-02-08 2:41 ` Lu Baolu
2022-02-08 15:01 ` Fenghua Yu
2022-02-10 3:16 ` Jacob Pan
2022-02-10 16:27 ` Fenghua Yu
2022-02-10 17:24 ` Luck, Tony
2022-02-10 18:31 ` Fenghua Yu
2022-02-10 23:52 ` Fenghua Yu
2022-02-10 18:49 ` Jacob Pan
2022-02-10 23:15 ` Fenghua Yu
2022-02-11 22:00 ` Dave Hansen
2022-02-14 17:24 ` Thomas Gleixner
2022-02-15 9:55 ` Joerg Roedel
[not found] ` <tencent_F6830A1196DB4C6A904D7C691F0D961D1108@qq.com>
2022-04-11 14:10 ` Dave Hansen
2022-04-11 14:20 ` zhangfei.gao
2022-04-11 14:36 ` Dave Hansen
2022-04-11 14:44 ` zhangfei.gao
2022-04-11 14:52 ` Dave Hansen
2022-04-11 15:13 ` zhangfei.gao
2022-04-12 7:04 ` zhangfei.gao
2022-04-12 13:41 ` Fenghua Yu
2022-04-12 14:39 ` Dave Hansen
2022-04-15 9:59 ` Fenghua Yu
2022-04-12 15:35 ` zhangfei.gao
2022-04-14 10:08 ` zhangfei.gao
2022-04-15 9:51 ` Fenghua Yu
[not found] ` <99bcb9f5-4776-9c40-a776-cdecfa9e1010@foxmail.com>
2022-04-15 10:14 ` zhangfei.gao
2022-04-15 10:50 ` Fenghua Yu
2022-04-15 11:52 ` zhangfei.gao
2022-04-15 12:37 ` Fenghua Yu
2022-04-16 1:30 ` zhangfei.gao
2022-04-15 19:07 ` Fenghua Yu
2022-04-15 21:00 ` Jacob Pan
2022-04-16 1:43 ` zhangfei.gao
2022-04-18 18:14 ` Jacob Pan
2022-04-19 1:02 ` zhangfei.gao
2022-04-18 6:34 ` Tian, Kevin
2022-04-18 18:11 ` Jacob Pan [this message]
2022-04-20 16:45 ` Jean-Philippe Brucker
2022-04-21 6:47 ` zhangfei.gao
2022-04-22 9:03 ` zhangfei.gao
2022-04-22 10:11 ` Jean-Philippe Brucker
2022-04-22 13:15 ` zhangfei.gao
2022-04-22 15:50 ` Jean-Philippe Brucker
2022-04-23 11:13 ` zhangfei.gao
2022-04-24 2:58 ` Zhangfei Gao
2022-04-24 9:52 ` Zhangfei Gao
2022-04-25 13:53 ` Jean-Philippe Brucker
2022-04-25 14:18 ` Dave Hansen
2022-04-25 14:26 ` Jean-Philippe Brucker
2022-04-25 15:34 ` Jacob Pan
2022-04-25 16:13 ` Jean-Philippe Brucker
2022-04-25 22:32 ` Jacob Pan
2022-04-26 4:20 ` Fenghua Yu
2022-04-26 5:04 ` Zhangfei Gao
2022-04-28 0:54 ` Fenghua Yu
2022-04-28 8:43 ` Jean-Philippe Brucker
2022-04-28 15:09 ` Dave Hansen
2022-04-28 15:28 ` Fenghua Yu
2022-04-28 15:42 ` Dave Hansen
2022-04-28 16:01 ` Jean-Philippe Brucker
2022-04-28 16:35 ` Dave Hansen
2022-04-26 4:28 ` Zhangfei Gao
2022-04-26 4:36 ` Fenghua Yu
2022-04-26 5:19 ` Zhangfei Gao
2022-04-25 15:55 ` Dave Hansen
2022-04-25 16:40 ` Jean-Philippe Brucker
2022-04-26 15:27 ` Dave Hansen
2022-04-26 16:48 ` Jean-Philippe Brucker
2022-04-26 23:31 ` Dave Hansen
2022-04-28 8:39 ` Jean-Philippe Brucker
2022-04-29 7:53 ` Baolu Lu
2022-04-29 13:51 ` Fenghua Yu
2022-04-29 14:34 ` Jean-Philippe Brucker
2022-04-29 22:19 ` Fenghua Yu
2022-04-30 7:33 ` Baolu Lu
2022-05-03 7:49 ` Jean-Philippe Brucker
2022-05-06 5:36 ` Baolu Lu
2022-04-12 14:36 ` Dave Hansen
2022-04-12 15:10 ` Jean-Philippe Brucker
2022-04-12 15:35 ` Dave Hansen
2022-04-13 11:14 ` Lu Baolu
2022-04-25 2:57 ` zhangfei.gao
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 06/11] x86/fpu: Clear PASID when copying fpstate Fenghua Yu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 07/11] sched: Define and initialize a flag to identify valid PASID in the task Fenghua Yu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Peter Zijlstra
2022-02-07 23:02 ` [PATCH v4 08/11] x86/traps: Demand-populate PASID MSR via #GP Fenghua Yu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 09/11] x86/cpufeatures: Re-enable ENQCMD Fenghua Yu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 10/11] tools/objtool: Check for use of the ENQCMD instruction in the kernel Fenghua Yu
2022-02-15 10:54 ` [tip: x86/pasid] " tip-bot2 for Fenghua Yu
2022-03-09 7:55 ` [tip: x86/core] " tip-bot2 for Fenghua Yu
2022-03-15 10:44 ` tip-bot2 for Fenghua Yu
2022-02-07 23:02 ` [PATCH v4 11/11] docs: x86: Change documentation for SVA (Shared Virtual Addressing) Fenghua Yu
2022-02-14 17:25 ` Thomas Gleixner
2022-02-15 10:54 ` [tip: x86/pasid] Documentation/x86: Update " tip-bot2 for Fenghua Yu
2022-02-11 20:04 ` [PATCH v4 00/11] Re-enable ENQCMD and PASID MSR Fenghua Yu
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