Re: [Xen-devel] [PATCH v13 0/4] add per-domain IOMMU control

From: Oleksandr <olekstysh@gmail.com>
To: Paul Durrant <Paul.Durrant@citrix.com>,
	'Jan Beulich' <jbeulich@suse.com>
Cc: Petre Pircalabu <ppircalabu@bitdefender.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	Wei Liu <wl@xen.org>,
	KonradRzeszutek Wilk <konrad.wilk@oracle.com>,
	Andrew Cooper <Andrew.Cooper3@citrix.com>,
	"Tim \(Xen.org\)" <tim@xen.org>,
	George Dunlap <George.Dunlap@citrix.com>,
	Julien Grall <julien.grall@arm.com>,
	Tamas K Lengyel <tamas@tklengyel.com>,
	David Scott <dave@recoil.org>,
	Anthony Perard <anthony.perard@citrix.com>,
	Ian Jackson <Ian.Jackson@citrix.com>,
	Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>,
	Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH v13 0/4] add per-domain IOMMU control
Date: Wed, 25 Sep 2019 19:24:10 +0300	[thread overview]
Message-ID: <5735846b-1a52-3260-39bd-e393c87dfb64@gmail.com> (raw)
In-Reply-To: <94de3adfac564f8e920bd04b3cf54734@AMSPEX02CL03.citrite.net>

On 25.09.19 19:10, Paul Durrant wrote:

Hi Paul

>> -----Original Message-----
>> From: Oleksandr <olekstysh@gmail.com>
>> Sent: 25 September 2019 16:50
>> To: Paul Durrant <Paul.Durrant@citrix.com>; 'Jan Beulich' <jbeulich@suse.com>
>> Cc: Petre Pircalabu <ppircalabu@bitdefender.com>; Stefano Stabellini <sstabellini@kernel.org>; Wei Liu
>> <wl@xen.org>; KonradRzeszutek Wilk <konrad.wilk@oracle.com>; Andrew Cooper
>> <Andrew.Cooper3@citrix.com>; David Scott <dave@recoil.org>; Tim (Xen.org) <tim@xen.org>; George Dunlap
>> <George.Dunlap@citrix.com>; Tamas K Lengyel <tamas@tklengyel.com>; Ian Jackson
>> <Ian.Jackson@citrix.com>; Anthony Perard <anthony.perard@citrix.com>; xen-devel@lists.xenproject.org;
>> Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>; Roger Pau Monne <roger.pau@citrix.com>; Julien Grall
>> <julien.grall@arm.com>
>> Subject: Re: [Xen-devel] [PATCH v13 0/4] add per-domain IOMMU control
>>
>>
>> [CC Julien]
>>
>>
>> Hi Paul
>>
>> I may mistake, but looks like
>>
>> 80ff3d338dc93260b41ffeeebb0f852c2edef9ce iommu: tidy up
>> iommu_use_hap_pt() and need_iommu_pt_sync() macros
>>
>> triggers ASSERT_UNREACHABLE on Arm if no IOMMU has been found (I built
>> with my platform's IOMMU driver disabled: # CONFIG_IPMMU_VMSA is not set) .
>>
>> So, iommu_setup() calls clear_iommu_hap_pt_share() with
>> iommu_hap_pt_share being set (CONFIG_IOMMU_FORCE_PT_SHARE=y) which,
>> actually, triggers ASSERT.
>>
> Here a minimal patch, leaving 'force pt share' in place. Does this avoid the problem?
>
> ---8<---
> diff --git a/xen/common/sysctl.c b/xen/common/sysctl.c
> index e8763c7fdf..f88a285e7f 100644
> --- a/xen/common/sysctl.c
> +++ b/xen/common/sysctl.c
> @@ -268,9 +268,11 @@ long do_sysctl(XEN_GUEST_HANDLE_PARAM(xen_sysctl_t) u_sysctl)
>           pi->max_mfn = get_upper_mfn_bound();
>           arch_do_physinfo(pi);
>           if ( iommu_enabled )
> +        {
>               pi->capabilities |= XEN_SYSCTL_PHYSCAP_directio;
> -        if ( iommu_hap_pt_share )
> -            pi->capabilities |= XEN_SYSCTL_PHYSCAP_iommu_hap_pt_share;
> +            if ( iommu_hap_pt_share )
> +                pi->capabilities |= XEN_SYSCTL_PHYSCAP_iommu_hap_pt_share;
> +        }
>
>           if ( copy_to_guest(u_sysctl, op, 1) )
>               ret = -EFAULT;
> diff --git a/xen/include/xen/iommu.h b/xen/include/xen/iommu.h
> index 7c3003f3f1..6a10a24128 100644
> --- a/xen/include/xen/iommu.h
> +++ b/xen/include/xen/iommu.h
> @@ -68,8 +68,6 @@ static inline void clear_iommu_hap_pt_share(void)
>   {
>   #ifndef iommu_hap_pt_share
>       iommu_hap_pt_share = false;
> -#elif iommu_hap_pt_share
> -    ASSERT_UNREACHABLE();
>   #endif
>   }
> ---8<---
>
>    Paul

Thank you for the patch, but I need some time to check it (now I have 
some troubles with starting guest VM). I will inform you once I check.

-- 
Regards,

Oleksandr Tyshchenko

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