Re: [Qemu-devel] [PATCH v2 1/3] s390x/pci: remove idx from msix msg data

[Yi Min Zhao <zyimin@linux.vnet.ibm.com>]

在 2017/9/5 下午4:29, Cornelia Huck 写道:
> On Fri,  1 Sep 2017 06:22:56 +0200
> Yi Min Zhao <zyimin@linux.vnet.ibm.com> wrote:
>
>> PCIDevice pointer has been a parameter of kvm_arch_fixup_msi_route().
>> So we don't need to store zpci idx in msix message data to find out the
>> specific zpci device. Instead, we could use pci device id to find its
>> corresponding zpci device.
>>
>> Signed-off-by: Yi Min Zhao <zyimin@linux.vnet.ibm.com>
>> ---
>>   hw/s390x/s390-pci-bus.c  | 16 +++++-----------
>>   hw/s390x/s390-pci-bus.h  |  2 ++
>>   hw/s390x/s390-pci-inst.c | 24 ------------------------
>>   hw/s390x/s390-pci-stub.c |  6 ++++++
>>   target/s390x/kvm.c       |  7 +++++--
>>   5 files changed, 18 insertions(+), 37 deletions(-)
>>
>> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
>> index 0a31a4ae88..bd8a3e1e1c 100644
>> --- a/hw/s390x/s390-pci-bus.c
>> +++ b/hw/s390x/s390-pci-bus.c
>> @@ -199,8 +199,8 @@ static S390PCIBusDevice *s390_pci_find_dev_by_uid(S390pciState *s, uint16_t uid)
>>       return NULL;
>>   }
>>   
>> -static S390PCIBusDevice *s390_pci_find_dev_by_target(S390pciState *s,
>> -                                                     const char *target)
>> +S390PCIBusDevice *s390_pci_find_dev_by_target(S390pciState *s,
>> +                                              const char *target)
>>   {
>>       S390PCIBusDevice *pbdev;
>>   
>> @@ -465,19 +465,13 @@ static void s390_msi_ctrl_write(void *opaque, hwaddr addr, uint64_t data,
>>                                   unsigned int size)
>>   {
>>       S390PCIBusDevice *pbdev = opaque;
>> -    uint32_t idx = data >> ZPCI_MSI_VEC_BITS;
>>       uint32_t vec = data & ZPCI_MSI_VEC_MASK;
>>       uint64_t ind_bit;
>>       uint32_t sum_bit;
>> -    uint32_t e = 0;
>>   
>> -    DPRINTF("write_msix data 0x%" PRIx64 " idx %d vec 0x%x\n", data, idx, vec);
>> -
>> -    if (!pbdev) {
>> -        e |= (vec << ERR_EVENT_MVN_OFFSET);
>> -        s390_pci_generate_error_event(ERR_EVENT_NOMSI, idx, 0, addr, e);
>> -        return;
>> -    }
>> +    assert(pbdev);
> I'm wondering whether you could/should generate an error event here.
> The one above probably won't work (as it seems to take idx as a
> parameter), but is this really 'this must not happen, we messed up in
> our code'? (Probably yes, but I want to be sure.)
I think this must not happen. One a pci device is plugged into zPCI bus.
We would assign a new memory region with zpci device as opaque
for its msix. So if s390_msi_ctrl_write() is called, there must be a write
operation to a pci device's msix ctrl memory region which must has zpci
device as a opaque. The construct is one-msi-mr-per-pci-device.
>
>> +    DPRINTF("write_msix data 0x%" PRIx64 " idx %d vec 0x%x\n", data,
>> +            pbdev->idx, vec);
>>   
>>       if (pbdev->state != ZPCI_FS_ENABLED) {
>>           return;
>> diff --git a/hw/s390x/s390-pci-stub.c b/hw/s390x/s390-pci-stub.c
>> index 7a642d376c..e501e1b9ea 100644
>> --- a/hw/s390x/s390-pci-stub.c
>> +++ b/hw/s390x/s390-pci-stub.c
>> @@ -74,3 +74,9 @@ S390PCIBusDevice *s390_pci_find_dev_by_idx(S390pciState *s, uint32_t idx)
>>   {
>>       return NULL;
>>   }
> Please remove s390_pci_find_dev_by_idx() from the stubs file, as it is
> not used outside of the conditionally-built pci code anymore.
I'm confused. s390_pci_find_dev_by_idx() can be called in 
kvm_arch_fixup_msi_route().
And kvm_arch_fixup_msi_route() can be called by kvm_irqchip_add_msi_route().
As the code, I think s390_pci_find_dev_by_idx() might be called. Could 
you please
explain more?
>
>> +
>> +S390PCIBusDevice *s390_pci_find_dev_by_target(S390pciState *s,
>> +                                              const char *target)
>> +{
>> +    return NULL;
>> +}
>> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
>> index 1338c29528..3d490c5e4b 100644
>> --- a/target/s390x/kvm.c
>> +++ b/target/s390x/kvm.c
>> @@ -2533,10 +2533,13 @@ int kvm_arch_fixup_msi_route(struct kvm_irq_routing_entry *route,
>>                                uint64_t address, uint32_t data, PCIDevice *dev)
>>   {
>>       S390PCIBusDevice *pbdev;
>> -    uint32_t idx = data >> ZPCI_MSI_VEC_BITS;
>>       uint32_t vec = data & ZPCI_MSI_VEC_MASK;
>>   
>> -    pbdev = s390_pci_find_dev_by_idx(s390_get_phb(), idx);
>> +    if (!dev) {
>> +        return -ENODEV;
> Can this actually happen?
I think this cannot happen. But I'm afraid that I miss something.
So I added this to avoid NULL pointer. But from the code and
my test, there has not been NULL pointer happened.
>
>> +    }
>> +
>> +    pbdev = s390_pci_find_dev_by_target(s390_get_phb(), DEVICE(dev)->id);
>>       if (!pbdev) {
>>           DPRINTF("add_msi_route no dev\n");
>>           return -ENODEV;
>