linux-kernel - Re: [PATCH v2 00/33] iommu: Move iommu

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Date:   Tue, 2 Jun 2020 07:16:22 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Clark <robdclark@...il.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        linux-s390@...r.kernel.org, linux-samsung-soc@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-rockchip@...ts.infradead.org,
        iommu@...ts.linux-foundation.org,
        linux-mediatek@...ts.infradead.org, linux-tegra@...r.kernel.org
Cc:     baolu.lu@...ux.intel.com
Subject: Re: [PATCH v2 00/33] iommu: Move iommu_group setup to IOMMU core code

Hi Jerry,

On 6/1/20 6:42 PM, Jerry Snitselaar wrote:
>>
>> Hi Joerg,
>>
>> With this patchset, I have an epyc system where if I boot with
>> iommu=nopt and force a dump I will see some io page faults for a nic
>> on the system. The vmcore is harvested and the system reboots. I
>> haven't reproduced it on other systems yet, but without the patchset I
>> don't see the io page faults during the kdump.
>>
>> Regards,
>> Jerry
> 
> I just hit an issue on a separate intel based system (kdump iommu=nopt),
> where it panics in during intel_iommu_attach_device, in is_aux_domain,
> due to device_domain_info being DEFER_DEVICE_DOMAIN_INFO. That doesn't
> get set to a valid address until the domain_add_dev_info call.
> 
> Is it as simple as the following?

I guess you won't hit this issue if you use iommu/next branch of Joerg's
tree. We've changed to use a generic helper to retrieve the valid per
device iommu data or NULL (if there's no).

Best regards,
baolu

> 
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 29d3940847d3..f1bbeed46a4c 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -5053,8 +5053,8 @@ is_aux_domain(struct device *dev, struct 
> iommu_domain *domain)
>   {
>          struct device_domain_info *info = dev->archdata.iommu;
> 
> -       return info && info->auxd_enabled &&
> -                       domain->type == IOMMU_DOMAIN_UNMANAGED;
> +       return info && info != DEFER_DEVICE_DOMAIN_INFO &&
> +               info->auxd_enabled && domain->type == 
> IOMMU_DOMAIN_UNMANAGED;
>   }
> 
>   static void auxiliary_link_device(struct dmar_domain *domain,
> 
> 
> Regards,
> Jerry