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

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Message-ID: <CABQgh9Fuh2HdBH7pyAteawZBpa55ZzfR9dv2K4RF=Ps4yhREbw@mail.gmail.com>
Date: Mon, 7 Apr 2025 20:08:57 +0800
From: Zhangfei Gao <zhangfei.gao@...aro.org>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: jgg@...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

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?

Thanks