Re: [RFC 04/37] KVM: s390: protvirt: Add initial lifecycle handling

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On 11/4/19 9:18 AM, Christian Borntraeger wrote:
> 
> 
> On 24.10.19 13:40, Janosch Frank wrote:
>> Let's add a KVM interface to create and destroy protected VMs.
>>
>> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
>> ---
>>  arch/s390/include/asm/kvm_host.h |  24 +++-
>>  arch/s390/include/asm/uv.h       | 110 ++++++++++++++
>>  arch/s390/kvm/Makefile           |   2 +-
>>  arch/s390/kvm/kvm-s390.c         | 173 +++++++++++++++++++++-
>>  arch/s390/kvm/kvm-s390.h         |  47 ++++++
>>  arch/s390/kvm/pv.c               | 237 +++++++++++++++++++++++++++++++
>>  include/uapi/linux/kvm.h         |  33 +++++
>>  7 files changed, 622 insertions(+), 4 deletions(-)
>>  create mode 100644 arch/s390/kvm/pv.c
> [...]
> 
>> +	case KVM_PV_VM_UNPACK: {
>> +		struct kvm_s390_pv_unp unp = {};
>> +
>> +		r = -EFAULT;
>> +		if (copy_from_user(&unp, argp, sizeof(unp)))
>> +			break;
>> +
>> +		r = kvm_s390_pv_unpack(kvm, unp.addr, unp.size, unp.tweak);
>> +		break;
>> +	}
> 
> 
> 
> [....]
> 
>> +int kvm_s390_pv_unpack(struct kvm *kvm, unsigned long addr, unsigned long size,
>> +		       unsigned long tweak)
>> +{
>> +	int i, rc = 0;
>> +	struct uv_cb_unp uvcb = {
>> +		.header.cmd = UVC_CMD_UNPACK_IMG,
>> +		.header.len = sizeof(uvcb),
>> +		.guest_handle = kvm_s390_pv_handle(kvm),
>> +		.tweak[0] = tweak
>> +	};
>> +
>> +	if (addr & ~PAGE_MASK || size & ~PAGE_MASK)
>> +		return -EINVAL;
>> +
>> +
>> +	VM_EVENT(kvm, 3, "PROTVIRT VM UNPACK: start addr %lx size %lx",
>> +		 addr, size);
> 
> Does it make sense to check for addr and addr+size to be within the memory
> size of the guest? The uv_call or gmap_fault will fail later on, but we 
> could do an early exit if the the site is wrong. 

Yeah, Marc already brought that up because of a testcase of his.
I'll add a check, but before that I need to understand what makes us
loop so long that we get RCU warnings.

> 
> 
> 
> 
>> +	for (i = 0; i < size / PAGE_SIZE; i++) {
>> +		uvcb.gaddr = addr + i * PAGE_SIZE;
>> +		uvcb.tweak[1] = i * PAGE_SIZE;
> 
> 
>> +retry:
> 
>> +		rc = uv_call(0, (u64)&uvcb);
>> +		if (!rc)
>> +			continue;
>> +		/* If not yet mapped fault and retry */
>> +		if (uvcb.header.rc == 0x10a) {
>> +			rc = gmap_fault(kvm->arch.gmap, uvcb.gaddr,
>> +					FAULT_FLAG_WRITE);
>> +			if (rc)
>> +				return rc;
>> +			goto retry;
>> +		}
>> +		VM_EVENT(kvm, 3, "PROTVIRT VM UNPACK: failed addr %llx rc %x rrc %x",
>> +			 uvcb.gaddr, uvcb.header.rc, uvcb.header.rrc);
>> +		break;
>> +	}
> [...]
> 


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