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 16:17:17 +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 16:16, Christian Borntraeger wrote:
> 
> 
> On 23.03.21 16:11, David Hildenbrand wrote:
>> 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.
> 
> Right, I think I can fix this up (and get rid of the local mso variable)
> when queueing. Or shall Claudio send a new version of the patch?
> 

IMHO, you can just fix it up.

-- 
Thanks,

David / dhildenb