linux-kernel - Re: [PATCH v2 2/2] s390/kvm: VSIE: fix MVPG handling for prefixing and MSO

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Date:   Tue, 23 Mar 2021 16:11:44 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Christian Borntraeger <borntraeger@...ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        linux-kernel@...r.kernel.org
Cc:     frankja@...ux.ibm.com, cohuck@...hat.com, kvm@...r.kernel.org,
        linux-s390@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2 2/2] s390/kvm: VSIE: fix MVPG handling for prefixing
 and MSO

On 23.03.21 16:07, Christian Borntraeger wrote:
> 
> 
> On 22.03.21 15:05, Claudio Imbrenda wrote:
>> Prefixing needs to be applied to the guest real address to translate it
>> into a guest absolute address.
>>
>> The value of MSO needs to be added to a guest-absolute address in order to
>> obtain the host-virtual.
>>
>> Fixes: 223ea46de9e79 ("s390/kvm: VSIE: correctly handle MVPG when in VSIE")
>> Cc: stable@...r.kernel.org
>> Signed-off-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
>> Reported-by: Janosch Frank <frankja@...ux.ibm.com>
>> ---
>>    arch/s390/kvm/vsie.c | 6 +++++-
>>    1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c
>> index 48aab6290a77..ac86f11e46dc 100644
>> --- a/arch/s390/kvm/vsie.c
>> +++ b/arch/s390/kvm/vsie.c
>> @@ -1002,7 +1002,7 @@ static u64 vsie_get_register(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page,
>>    static int vsie_handle_mvpg(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>>    {
>>    	struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s;
>> -	unsigned long pei_dest, pei_src, src, dest, mask;
>> +	unsigned long pei_dest, pei_src, dest, src, mask, mso, prefix;
>>    	u64 *pei_block = &vsie_page->scb_o->mcic;
>>    	int edat, rc_dest, rc_src;
>>    	union ctlreg0 cr0;
>> @@ -1010,9 +1010,13 @@ static int vsie_handle_mvpg(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
>>    	cr0.val = vcpu->arch.sie_block->gcr[0];
>>    	edat = cr0.edat && test_kvm_facility(vcpu->kvm, 8);
>>    	mask = _kvm_s390_logical_to_effective(&scb_s->gpsw, PAGE_MASK);
>> +	mso = scb_s->mso & ~(1UL << 20);
> 			shouldnt that be ~((1UL << 20 ) -1)
> 

Looking at shadow_scb(), we can simply take scb_s->mso unmodified.

-- 
Thanks,

David / dhildenb