iommu.lists.linux-foundation.org archive mirror
 help / color / mirror / Atom feed
From: Jacob Pan <jacob.jun.pan@intel.com>
To: Fenghua Yu <fenghua.yu@intel.com>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>,
	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@intel.com
Subject: Re: [PATCH v6 08/12] fork: Clear PASID for new mm
Date: Mon, 1 Mar 2021 15:00:11 -0800	[thread overview]
Message-ID: <20210301150011.766e70a3@jacob-builder> (raw)
In-Reply-To: <YDgh53AcQHT+T3L0@otcwcpicx3.sc.intel.com>

Hi Fenghua,

On Thu, 25 Feb 2021 22:17:11 +0000, Fenghua Yu <fenghua.yu@intel.com> wrote:

> 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
We should consolidate at some point, there is no need to store pasid in two
places.

> functionality is not a problem without this patch on x86. But I think
I feel the reason that x86 doesn't care is that mm->pasid is not used
unless bind_mm is called. For the fork children even mm->pasid is non-zero,
it has no effect since it is not loaded onto MSRs.
Perhaps you could also add a check or WARN_ON(!mm->pasid) in load_pasid()?

> 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.
> 
Agreed.

> Who will accept this patch?
> 
> Thanks.
> 
> -Fenghua


Thanks,

Jacob
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2021-03-01 22:58 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
2021-03-01 23:00       ` Jacob Pan [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210301150011.766e70a3@jacob-builder \
    --to=jacob.jun.pan@intel.com \
    --cc=ashok.raj@intel.com \
    --cc=fenghua.yu@intel.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=jean-philippe@linaro.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=zhangfei.gao@foxmail.com \
    --subject='Re: [PATCH v6 08/12] fork: Clear PASID for new mm' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).