linux-kernel - Re: [PATCH v2 1/4] iommu/vt-d: Enable write protect for supervisor SVM

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Message-ID: <d43efcb9-23bd-bea4-1b27-429a171dcb65@roeck-us.net>
Date:   Tue, 30 Mar 2021 12:02:17 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        iommu@...ts.linux-foundation.org, Joerg Roedel <joro@...tes.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Sanjay Kumar <sanjay.k.kumar@...el.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Luck, Tony" <tony.luck@...el.com>
Subject: Re: [PATCH v2 1/4] iommu/vt-d: Enable write protect for supervisor
 SVM

On 3/30/21 10:52 AM, Jacob Pan wrote:
> Hi Guenter,
> 
> On Mon, 22 Mar 2021 10:53:38 -0700, Guenter Roeck <linux@...ck-us.net>
> wrote:
> 
>> On Tue, Mar 02, 2021 at 02:13:57AM -0800, Jacob Pan wrote:
>>> Write protect bit, when set, inhibits supervisor writes to the read-only
>>> pages. In supervisor shared virtual addressing (SVA), where page tables
>>> are shared between CPU and DMA, IOMMU PASID entry WPE bit should match
>>> CR0.WP bit in the CPU.
>>> This patch sets WPE bit for supervisor PASIDs if CR0.WP is set.
>>>
>>> Signed-off-by: Sanjay Kumar <sanjay.k.kumar@...el.com>
>>> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
>>> ---  
>>
>> ia64:defconfig:
>>
>> drivers/iommu/intel/pasid.c: In function 'pasid_enable_wpe':
>> drivers/iommu/intel/pasid.c:536:22: error: implicit declaration of
>> function 'read_cr0' drivers/iommu/intel/pasid.c:539:23: error:
>> 'X86_CR0_WP' undeclared
>>
>> Maybe it _is_ time to retire ia64 ?
> 
> Good catch, sorry for the late reply. I guess otherwise I will have to do
> some #ifdef?
> 

I really can't tell you how to resolve this.

> There are many basic x86 helpers are missing in ia64.
> 
I'd say that Intel needs to decide what to do with the ia64 architecture.

Guenter

> +Tony
> 
> Thanks,
> 
> Jacob
>