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From: Fenghua Yu <fenghua.yu@intel.com>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: Ashok Raj <ashok.raj@intel.com>,
	zhangfei.gao@foxmail.com,
	linux-kernel <linux-kernel@vger.kernel.org>,
	linux-mm@kvack.org, iommu@lists.linux-foundation.org,
	Jacob Jun Pan <jacob.jun.pan@intel.com>
Subject: Re: [PATCH v6 08/12] fork: Clear PASID for new mm
Date: Thu, 25 Feb 2021 22:17:11 +0000	[thread overview]
Message-ID: <YDgh53AcQHT+T3L0@otcwcpicx3.sc.intel.com> (raw)
In-Reply-To: <YDYoL/zZ9YaGgwSV@myrica>

Hi, Jean,

On Wed, Feb 24, 2021 at 11:19:27AM +0100, Jean-Philippe Brucker wrote:
> Hi Fenghua,
> 
> [Trimmed the Cc list]
> 
> On Mon, Jul 13, 2020 at 04:48:03PM -0700, Fenghua Yu wrote:
> > When a new mm is created, its PASID should be cleared, i.e. the PASID is
> > initialized to its init state 0 on both ARM and X86.
> 
> I just noticed this patch was dropped in v7, and am wondering whether we
> could still upstream it. Does x86 need a child with a new address space
> (!CLONE_VM) to inherit the PASID of the parent?  That doesn't make much
> sense with regard to IOMMU structures - same PASID indexing multiple PGDs?

You are right: x86 should clear mm->pasid when a new mm is created.
This patch somehow is losted:(

> 
> Currently iommu_sva_alloc_pasid() assumes mm->pasid is always initialized
> to 0 and fails on forked tasks. I'm trying to figure out how to fix this.
> Could we clear the pasid on fork or does it break the x86 model?

x86 calls ioasid_alloc() instead of iommu_sva_alloc_pasid(). So
functionality is not a problem without this patch on x86. But I think
we do need to have this patch in the kernel because PASID is per addr
space and two addr spaces shouldn't have the same PASID.

Who will accept this patch?

Thanks.

-Fenghua
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  reply	other threads:[~2021-02-25 22:17 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-13 23:47 [PATCH v6 00/12] x86: tag application address space for devices Fenghua Yu
2020-07-13 23:47 ` [PATCH v6 01/12] iommu: Change type of pasid to u32 Fenghua Yu
2020-07-14  2:45   ` Liu, Yi L
2020-07-14 13:54     ` Fenghua Yu
2020-07-14 13:56       ` Liu, Yi L
2020-07-22 14:03   ` Joerg Roedel
2020-07-22 17:21     ` Fenghua Yu
2020-07-13 23:47 ` [PATCH v6 02/12] iommu/vt-d: Change flags type to unsigned int in binding mm Fenghua Yu
2020-07-13 23:47 ` [PATCH v6 03/12] docs: x86: Add documentation for SVA (Shared Virtual Addressing) Fenghua Yu
2020-07-14  3:25   ` Liu, Yi L
2020-07-15 23:32     ` Fenghua Yu
2020-07-13 23:47 ` [PATCH v6 04/12] x86/cpufeatures: Enumerate ENQCMD and ENQCMDS instructions Fenghua Yu
2020-07-13 23:48 ` [PATCH v6 05/12] x86/fpu/xstate: Add supervisor PASID state for ENQCMD feature Fenghua Yu
2020-07-13 23:48 ` [PATCH v6 06/12] x86/msr-index: Define IA32_PASID MSR Fenghua Yu
2020-07-13 23:48 ` [PATCH v6 07/12] mm: Define pasid in mm Fenghua Yu
2020-07-13 23:48 ` [PATCH v6 08/12] fork: Clear PASID for new mm Fenghua Yu
2021-02-24 10:19   ` Jean-Philippe Brucker
2021-02-25 22:17     ` Fenghua Yu [this message]
2021-03-01 23:00       ` Jacob Pan
2021-03-02 10:43         ` Jean-Philippe Brucker
2020-07-13 23:48 ` [PATCH v6 09/12] x86/process: Clear PASID state for a newly forked/cloned thread Fenghua Yu
2020-08-01  1:44   ` Andy Lutomirski
2020-07-13 23:48 ` [PATCH v6 10/12] x86/mmu: Allocate/free PASID Fenghua Yu
2020-07-13 23:48 ` [PATCH v6 11/12] sched: Define and initialize a flag to identify valid PASID in the task Fenghua Yu
2020-07-13 23:48 ` [PATCH v6 12/12] x86/traps: Fix up invalid PASID Fenghua Yu
2020-07-31 23:34   ` Andy Lutomirski
2020-08-01  0:42     ` Fenghua Yu
2020-08-03 15:03     ` Dave Hansen
2020-08-03 15:12       ` Andy Lutomirski
2020-08-03 15:19         ` Raj, Ashok
2020-08-03 16:36         ` Dave Hansen
2020-08-03 17:16           ` Andy Lutomirski
2020-08-03 17:34             ` Dave Hansen
2020-08-03 19:24               ` Andy Lutomirski
2020-08-01  1:28   ` Andy Lutomirski
2020-08-03 17:19     ` Fenghua Yu

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