linux-kernel - Re: [PATCH] KVM: arm/arm64: vgic-its: Fix restoration of unmapped collections

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Date:   Fri, 13 Dec 2019 18:53:53 +0800
From:   Zenghui Yu <yuzenghui@...wei.com>
To:     Eric Auger <eric.auger@...hat.com>, <eric.auger.pro@...il.com>,
        <maz@...nel.org>, <linux-kernel@...r.kernel.org>,
        <kvmarm@...ts.cs.columbia.edu>
Subject: Re: [PATCH] KVM: arm/arm64: vgic-its: Fix restoration of unmapped
 collections

Hi Eric,

On 2019/12/13 17:42, Eric Auger wrote:
> Saving/restoring an unmapped collection is a valid scenario. For
> example this happens if a MAPTI command was sent, featuring an
> unmapped collection. At the moment the CTE fails to be restored.
> Only compare against the number of online vcpus if the rdist
> base is set.

Have you actually seen a problem and this patch fixed it? To be honest,
I'm surprised to find that we can map a LPI to an unmapped collection ;)
(and prevent it to be delivered to vcpu with an INT_UNMAPPED_INTERRUPT
error, until someone had actually mapped the collection).
After a quick glance of spec (MAPTI), just as you said, this is valid.

If Marc has no objection to this fix, please add

Reviewed-by: Zenghui Yu <yuzenghui@...wei.com>


Thanks,
Zenghui

> 
> Cc: stable@...r.kernel.org # v4.11+
> Fixes: ea1ad53e1e31a ("KVM: arm64: vgic-its: Collection table save/restore")
> Signed-off-by: Eric Auger <eric.auger@...hat.com>
> ---
>   virt/kvm/arm/vgic/vgic-its.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 98c7360d9fb7..17920d1b350a 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -2475,7 +2475,8 @@ static int vgic_its_restore_cte(struct vgic_its *its, gpa_t gpa, int esz)
>   	target_addr = (u32)(val >> KVM_ITS_CTE_RDBASE_SHIFT);
>   	coll_id = val & KVM_ITS_CTE_ICID_MASK;
>   
> -	if (target_addr >= atomic_read(&kvm->online_vcpus))
> +	if (target_addr != COLLECTION_NOT_MAPPED &&
> +	    target_addr >= atomic_read(&kvm->online_vcpus))
>   		return -EINVAL;
>   
>   	collection = find_collection(its, coll_id);
>