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Subject: Re: [PATCH v4 2/2] s390: virtio: PV needs VIRTIO I/O device
 protection
To:     Christian Borntraeger <borntraeger@de.ibm.com>,
        linux-kernel@vger.kernel.org
Cc:     pasic@linux.ibm.com, frankja@linux.ibm.com, mst@redhat.com,
        jasowang@redhat.com, cohuck@redhat.com, kvm@vger.kernel.org,
        linux-s390@vger.kernel.org,
        virtualization@lists.linux-foundation.org, thomas.lendacky@amd.com,
        david@gibson.dropbear.id.au, linuxram@us.ibm.com,
        heiko.carstens@de.ibm.com, gor@linux.ibm.com
References: <1594111477-15401-1-git-send-email-pmorel@linux.ibm.com>
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 <862dce70-1aed-ace0-cb7b-54844e812be3@de.ibm.com>
From:   Pierre Morel <pmorel@linux.ibm.com>
Message-ID: <dbf28573-2100-20ed-9e8b-8e6d1795ec44@linux.ibm.com>
Date:   Tue, 7 Jul 2020 13:16:53 +0200
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On 2020-07-07 13:12, Christian Borntraeger wrote:
> 
> 
> On 07.07.20 10:44, Pierre Morel wrote:
>> S390, protecting the guest memory against unauthorized host access
>> needs to enforce VIRTIO I/O device protection through the use of
>> VIRTIO_F_VERSION_1 and VIRTIO_F_IOMMU_PLATFORM.
>>
>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>> ---
>>   arch/s390/kernel/uv.c | 25 +++++++++++++++++++++++++
>>   1 file changed, 25 insertions(+)
>>
>> diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
>> index c296e5c8dbf9..106330f6eda1 100644
>> --- a/arch/s390/kernel/uv.c
>> +++ b/arch/s390/kernel/uv.c
>> @@ -14,6 +14,7 @@
>>   #include <linux/memblock.h>
>>   #include <linux/pagemap.h>
>>   #include <linux/swap.h>
>> +#include <linux/virtio_config.h>
>>   #include <asm/facility.h>
>>   #include <asm/sections.h>
>>   #include <asm/uv.h>
>> @@ -413,3 +414,27 @@ static int __init uv_info_init(void)
>>   }
>>   device_initcall(uv_info_init);
>>   #endif
>> +
>> +/*
>> + * arch_validate_virtio_iommu_platform
>> + * @dev: the VIRTIO device being added
>> + *
>> + * Return value: returns -ENODEV if any features of the
>> + *               device breaks the protected virtualization
>> + *               0 otherwise.
>> + */
>> +int arch_validate_virtio_features(struct virtio_device *dev)
>> +{
>> +	if (!virtio_has_feature(dev, VIRTIO_F_VERSION_1)) {
>> +		dev_warn(&dev->dev, "device must provide VIRTIO_F_VERSION_1\n");
> 
> I think you only want to warn if is_prot_virt_guest is true? We certainly
> want to be able to run as a guest of older hypervisors with virtio 0.95, no?

clear, yes.
I will first check for PV as Connie sugested.

> 
> 
>> +		return is_prot_virt_guest() ? -ENODEV : 0;
>> +	}
>> +
>> +	if (!virtio_has_feature(dev, VIRTIO_F_IOMMU_PLATFORM)) {
>> +		dev_warn(&dev->dev,
>> +			 "device must provide VIRTIO_F_IOMMU_PLATFORM\n");
> 
> same here.

Yes,
Thanks,

Pierre

-- 
Pierre Morel
IBM Lab Boeblingen