[Xen-devel] Ping: [PATCH v2] x86/HVM: p2m_ram_ro is incompatible with device pass-through

[Jan Beulich <JBeulich@xxxxxxxx>]

On 03.07.2019 13:36, Jan Beulich wrote:
> The write-discard property of the type can't be represented in IOMMU
> page table entries. Make sure the respective checks / tracking can't
> race, by utilizing the domain lock. The other sides of the sharing/
> paging/log-dirty exclusion checks should subsequently perhaps also be
> put under that lock then.
> 
> Take the opportunity and also convert neighboring bool_t to bool in
> struct hvm_domain.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Alongside Paul's R-b could I get an ack or otherwise from you?

Thanks, Jan

> ---
> v2: Don't set p2m_ram_ro_used when failing the request.
> 
> --- a/xen/arch/x86/hvm/dm.c
> +++ b/xen/arch/x86/hvm/dm.c
> @@ -255,16 +255,33 @@ static int set_mem_type(struct domain *d
>    
>        mem_type = array_index_nospec(data->mem_type, ARRAY_SIZE(memtype));
>    
> -    if ( mem_type == HVMMEM_ioreq_server )
> +    switch ( mem_type )
>        {
>            unsigned int flags;
>    
> +    case HVMMEM_ioreq_server:
>            if ( !hap_enabled(d) )
>                return -EOPNOTSUPP;
>    
>            /* Do not change to HVMMEM_ioreq_server if no ioreq server mapped. 
> */
>            if ( !p2m_get_ioreq_server(d, &flags) )
>                return -EINVAL;
> +
> +        break;
> +
> +    case HVMMEM_ram_ro:
> +        /* p2m_ram_ro can't be represented in IOMMU mappings. */
> +        domain_lock(d);
> +        if ( has_iommu_pt(d) )
> +            rc = -EXDEV;
> +        else
> +            d->arch.hvm.p2m_ram_ro_used = true;
> +        domain_unlock(d);
> +
> +        if ( rc )
> +            return rc;
> +
> +        break;
>        }
>    
>        while ( iter < data->nr )
> --- a/xen/drivers/passthrough/pci.c
> +++ b/xen/drivers/passthrough/pci.c
> @@ -1448,17 +1448,36 @@ static int assign_device(struct domain *
>        if ( !iommu_enabled || !hd->platform_ops )
>            return 0;
>    
> -    /* Prevent device assign if mem paging or mem sharing have been
> -     * enabled for this domain */
> -    if ( unlikely(d->arch.hvm.mem_sharing_enabled ||
> -                  vm_event_check_ring(d->vm_event_paging) ||
> +    domain_lock(d);
> +
> +    /*
> +     * Prevent device assignment if any of
> +     * - mem paging
> +     * - mem sharing
> +     * - the p2m_ram_ro type
> +     * - global log-dirty mode
> +     * are in use by this domain.
> +     */
> +    if ( unlikely(vm_event_check_ring(d->vm_event_paging) ||
> +#ifdef CONFIG_HVM
> +                  (is_hvm_domain(d) &&
> +                   (d->arch.hvm.mem_sharing_enabled ||
> +                    d->arch.hvm.p2m_ram_ro_used)) ||
> +#endif
>                      p2m_get_hostp2m(d)->global_logdirty) )
> +    {
> +        domain_unlock(d);
>            return -EXDEV;
> +    }
>    
>        if ( !pcidevs_trylock() )
> +    {
> +        domain_unlock(d);
>            return -ERESTART;
> +    }
>    
>        rc = iommu_construct(d);
> +    domain_unlock(d);
>        if ( rc )
>        {
>            pcidevs_unlock();
> --- a/xen/include/asm-x86/hvm/domain.h
> +++ b/xen/include/asm-x86/hvm/domain.h
> @@ -156,10 +156,11 @@ struct hvm_domain {
>    
>        struct viridian_domain *viridian;
>    
> -    bool_t                 hap_enabled;
> -    bool_t                 mem_sharing_enabled;
> -    bool_t                 qemu_mapcache_invalidate;
> -    bool_t                 is_s3_suspended;
> +    bool                   hap_enabled;
> +    bool                   mem_sharing_enabled;
> +    bool                   p2m_ram_ro_used;
> +    bool                   qemu_mapcache_invalidate;
> +    bool                   is_s3_suspended;
>    
>        /*
>         * TSC value that VCPUs use to calculate their tsc_offset value.
> _______________________________________________
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> Xen-devel@xxxxxxxxxxxxxxxxxxxx
> https://lists.xenproject.org/mailman/listinfo/xen-devel
> 

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