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Subject: Re: [PATCH] KVM: arm/arm64: vgic-its: Fix restoration of unmapped
 collections
To:     Zenghui Yu <yuzenghui@huawei.com>, eric.auger.pro@gmail.com,
        maz@kernel.org, linux-kernel@vger.kernel.org,
        kvmarm@lists.cs.columbia.edu
References: <20191213094237.19627-1-eric.auger@redhat.com>
 <d36b75e7-bd83-e501-3bd4-76bf0489c5ce@huawei.com>
From:   Auger Eric <eric.auger@redhat.com>
Message-ID: <604a28ab-3a4a-4b9f-a9fa-719edc915d0d@redhat.com>
Date:   Fri, 13 Dec 2019 12:06:36 +0100
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Hi Zenghui,

On 12/13/19 11:53 AM, Zenghui Yu wrote:
> Hi Eric,
>=20
> 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.
>=20
> Have you actually seen a problem and this patch fixed it?

It is not with a linux guest but with kvm-unit-test.

 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.
>=20
> If Marc has no objection to this fix, please add
>=20
> Reviewed-by: Zenghui Yu <yuzenghui@huawei.com>
Thank you for the review.

Eric
>=20
>=20
> Thanks,
> Zenghui
>=20
>>
>> Cc: stable@vger.kernel.org # v4.11+
>> Fixes: ea1ad53e1e31a ("KVM: arm64: vgic-its: Collection table
>> save/restore")
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>> ---
>> =C2=A0 virt/kvm/arm/vgic/vgic-its.c | 3 ++-
>> =C2=A0 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)
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 target_addr =3D (u32)(val >> KVM_ITS_CT=
E_RDBASE_SHIFT);
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 coll_id =3D val & KVM_ITS_CTE_ICID_MASK=
;
>> =C2=A0 -=C2=A0=C2=A0=C2=A0 if (target_addr >=3D atomic_read(&kvm->onli=
ne_vcpus))
>> +=C2=A0=C2=A0=C2=A0 if (target_addr !=3D COLLECTION_NOT_MAPPED &&
>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 target_addr >=3D atomic_re=
ad(&kvm->online_vcpus))
>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 return -EINVAL;
>> =C2=A0 =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 collection =3D find_collection(i=
ts, coll_id);
>>
>=20