linux-kernel - Re: [PATCH v8 12/14] iommu/arm-smmu-v3: Introduce struct arm_smmu

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Message-ID: <20250407171702.GK1557073@nvidia.com>
Date: Mon, 7 Apr 2025 14:17:02 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Zhangfei Gao <zhangfei.gao@...aro.org>
Cc: Nicolin Chen <nicolinc@...dia.com>, kevin.tian@...el.com,
	corbet@....net, will@...nel.org, joro@...tes.org,
	suravee.suthikulpanit@....com, robin.murphy@....com,
	dwmw2@...radead.org, baolu.lu@...ux.intel.com,
	linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kselftest@...r.kernel.org, linux-doc@...r.kernel.org,
	eric.auger@...hat.com, jean-philippe@...aro.org, mdf@...nel.org,
	mshavit@...gle.com, shameerali.kolothum.thodi@...wei.com,
	smostafa@...gle.com, ddutile@...hat.com, yi.l.liu@...el.com,
	praan@...gle.com, patches@...ts.linux.dev
Subject: Re: [PATCH v8 12/14] iommu/arm-smmu-v3: Introduce struct
 arm_smmu_vmaster

On Mon, Apr 07, 2025 at 08:08:57PM +0800, Zhangfei Gao wrote:
> Hi, Nico
> 
> On Wed, 26 Feb 2025 at 01:35, Nicolin Chen <nicolinc@...dia.com> wrote:
> >
> > Use it to store all vSMMU-related data. The vsid (Virtual Stream ID) will
> > be the first use case. Since the vsid reader will be the eventq handler
> > that already holds a streams_mutex, reuse that to fenche the vmaster too.
> >
> > Also add a pair of arm_smmu_attach_prepare/commit_vmaster helpers to set
> > or unset the master->vmaster point. Put these helpers inside the existing
> > arm_smmu_attach_prepare/commit().
> >
> > For identity/blocked ops that don't call arm_smmu_attach_prepare/commit(),
> > add a simpler arm_smmu_master_clear_vmaster helper to unset the vmaster.
> >
> > Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> > Reviewed-by: Pranjal Shrivastavat <praan@...gle.com>
> > Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
> > ---
> 
> >
> > +int arm_smmu_attach_prepare_vmaster(struct arm_smmu_attach_state *state,
> > +                                   struct arm_smmu_nested_domain *nested_domain)
> > +{
> > +       struct arm_smmu_vmaster *vmaster;
> > +       unsigned long vsid;
> > +       int ret;
> > +
> > +       iommu_group_mutex_assert(state->master->dev);
> > +
> > +       /* Skip invalid vSTE */
> > +       if (!(nested_domain->ste[0] & cpu_to_le64(STRTAB_STE_0_V)))
> > +               return 0;
> 
> Why this is removed in v9 and 6.15-rc1?
> 
> I tested 6.15-rc1 the qemu failed to boot with qemu branch:
> for_iommufd_veventq-v8
> "failed to attach the bypass pagetable"
> 
> After adding this "skip check" back, the qemu works again.
> 
> Do we need to add this back?

Shouldn't need too.. Do you know what failed to cause the failed to
attach? There is nothing in this function that should cause that.

Jason