Re: [Xen-devel] [PATCH v6 08/10] remove late (on-demand) construction of IOMMU page tables

From: Jan Beulich <jbeulich@suse.com>
To: Paul Durrant <paul.durrant@citrix.com>
Cc: "Petre Pircalabu" <ppircalabu@bitdefender.com>,
	"Stefano Stabellini" <sstabellini@kernel.org>,
	"Wei Liu" <wl@xen.org>,
	"Razvan Cojocaru" <rcojocaru@bitdefender.com>,
	"KonradRzeszutek Wilk" <konrad.wilk@oracle.com>,
	"George Dunlap" <george.dunlap@eu.citrix.com>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Ian Jackson" <ian.jackson@eu.citrix.com>,
	"Tim Deegan" <tim@xen.org>, "Julien Grall" <julien.grall@arm.com>,
	"Tamas K Lengyel" <tamas@tklengyel.com>,
	"Alexandru Isaila" <aisaila@bitdefender.com>,
	xen-devel@lists.xenproject.org,
	"Volodymyr Babchuk" <Volodymyr_Babchuk@epam.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH v6 08/10] remove late (on-demand) construction of IOMMU page tables
Date: Thu, 29 Aug 2019 15:39:23 +0200	[thread overview]
Message-ID: <7ac91f71-eac4-bf13-ff01-09fe4d9b7376@suse.com> (raw)
In-Reply-To: <20190816172001.3905-9-paul.durrant@citrix.com>

On 16.08.2019 19:19, Paul Durrant wrote:
> --- a/xen/drivers/passthrough/iommu.c
> +++ b/xen/drivers/passthrough/iommu.c
> @@ -146,6 +146,17 @@ static int __init parse_dom0_iommu_param(const char *s)
>  }
>  custom_param("dom0-iommu", parse_dom0_iommu_param);
>  
> +static void __hwdom_init check_hwdom_reqs(struct domain *d)

This really should have const, but I realize ...

> +{
> +    if ( iommu_hwdom_none || !paging_mode_translate(d) )
> +        return;
> +
> +    arch_iommu_check_autotranslated_hwdom(d);

... this one wants non-const (for - afaict - no reason).

> @@ -159,129 +170,44 @@ int iommu_domain_init(struct domain *d)
>          return ret;
>  
>      hd->platform_ops = iommu_get_ops();
> -    return hd->platform_ops->init(d);
> -}
> +    ret = hd->platform_ops->init(d);
> +    if ( ret )
> +        return ret;
>  
> -static void __hwdom_init check_hwdom_reqs(struct domain *d)
> -{
> -    if ( iommu_hwdom_none || !paging_mode_translate(d) )
> -        return;
> +    /*
> +     * NB: 'relaxed' h/w domains don't need the IOMMU mappings to be kept
> +     *     in-sync with their assigned pages because all host RAM will be
> +     *     mapped during hwdom_init().
> +     */

Doesn't this comment belong to ...

> +    if ( is_hardware_domain(d) )
> +        check_hwdom_reqs(d); /* may modify iommu_hwdom_strict */
>  
> -    arch_iommu_check_autotranslated_hwdom(d);
> +    if ( !is_hardware_domain(d) || iommu_hwdom_strict )
> +        hd->need_sync = !iommu_use_hap_pt(d);

... this if()?

> @@ -629,8 +552,7 @@ static void iommu_dump_p2m_table(unsigned char key)
>      ops = iommu_get_ops();
>      for_each_domain(d)
>      {
> -        if ( is_hardware_domain(d) ||
> -             dom_iommu(d)->status < IOMMU_STATUS_initialized )
> +        if ( !is_iommu_enabled(d) )
>              continue;

Didn't you agree to retain the hwdom part of the condition here?

Jan

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