Re: [PATCH 4/6] KVM: s390: fix sigp set prefix status stored cases
Am 26.06.2012 um 17:39 schrieb Cornelia Huck :
> On Tue, 26 Jun 2012 16:56:08 +0200
> Alexander Graf wrote:
>
>>
>> On 26.06.2012, at 16:06, Cornelia Huck wrote:
>>
>>> From: Heiko Carstens
>>>
>>> If an invalid parameter is passed or the addressed cpu is in an
>>> incorrect state sigp set prefix will store a status.
>>> This status must only have bits set as defined by the architecture.
>>> The current kvm implementation missed to clear bits and also did
>>> not set the intended status bit ("and" instead of "or" operation).
>>>
>>> Signed-off-by: Heiko Carstens
>>> Signed-off-by: Cornelia Huck
>>
>> What was the net effect of this for a guest? Any problems rising from it?
>
> The guest might see some unexpected status bits if it did call sigp set
> prefix in an incorrect way. I'm not aware that anybody has actually
> seen that.
Yeah, we only need the set prefix on vm init and here it should always succeed,
so this one is not all that urgent :).
Alex
>
> Cornelia
>
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Re: [PATCH 4/6] KVM: s390: fix sigp set prefix status stored cases
On Tue, 26 Jun 2012 16:56:08 +0200
Alexander Graf wrote:
>
> On 26.06.2012, at 16:06, Cornelia Huck wrote:
>
> > From: Heiko Carstens
> >
> > If an invalid parameter is passed or the addressed cpu is in an
> > incorrect state sigp set prefix will store a status.
> > This status must only have bits set as defined by the architecture.
> > The current kvm implementation missed to clear bits and also did
> > not set the intended status bit ("and" instead of "or" operation).
> >
> > Signed-off-by: Heiko Carstens
> > Signed-off-by: Cornelia Huck
>
> What was the net effect of this for a guest? Any problems rising from it?
The guest might see some unexpected status bits if it did call sigp set
prefix in an incorrect way. I'm not aware that anybody has actually
seen that.
Cornelia
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Re: [PATCH 4/6] KVM: s390: fix sigp set prefix status stored cases
On 26.06.2012, at 16:06, Cornelia Huck wrote:
> From: Heiko Carstens
>
> If an invalid parameter is passed or the addressed cpu is in an
> incorrect state sigp set prefix will store a status.
> This status must only have bits set as defined by the architecture.
> The current kvm implementation missed to clear bits and also did
> not set the intended status bit ("and" instead of "or" operation).
>
> Signed-off-by: Heiko Carstens
> Signed-off-by: Cornelia Huck
What was the net effect of this for a guest? Any problems rising from it?
Alex
> ---
> arch/s390/kvm/sigp.c |7 +--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/arch/s390/kvm/sigp.c b/arch/s390/kvm/sigp.c
> index caccc0e..ca544d5 100644
> --- a/arch/s390/kvm/sigp.c
> +++ b/arch/s390/kvm/sigp.c
> @@ -207,6 +207,7 @@ static int __sigp_set_prefix(struct kvm_vcpu *vcpu, u16
> cpu_addr, u32 address,
> address = address & 0x7fffe000u;
> if (copy_from_guest_absolute(vcpu, &tmp, address, 1) ||
> copy_from_guest_absolute(vcpu, &tmp, address + PAGE_SIZE, 1)) {
> + *reg &= 0xUL;
> *reg |= SIGP_STATUS_INVALID_PARAMETER;
> return 1; /* invalid parameter */
> }
> @@ -220,8 +221,9 @@ static int __sigp_set_prefix(struct kvm_vcpu *vcpu, u16
> cpu_addr, u32 address,
> li = fi->local_int[cpu_addr];
>
> if (li == NULL) {
> + *reg &= 0xUL;
> + *reg |= SIGP_STATUS_INCORRECT_STATE;
> rc = 1; /* incorrect state */
> - *reg &= SIGP_STATUS_INCORRECT_STATE;
> kfree(inti);
> goto out_fi;
> }
> @@ -229,8 +231,9 @@ static int __sigp_set_prefix(struct kvm_vcpu *vcpu, u16
> cpu_addr, u32 address,
> spin_lock_bh(&li->lock);
> /* cpu must be in stopped state */
> if (!(atomic_read(li->cpuflags) & CPUSTAT_STOPPED)) {
> + *reg &= 0xUL;
> + *reg |= SIGP_STATUS_INCORRECT_STATE;
> rc = 1; /* incorrect state */
> - *reg &= SIGP_STATUS_INCORRECT_STATE;
> kfree(inti);
> goto out_li;
> }
> --
> 1.7.10.4
>
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