On 7/24/26 3:10 PM, Farhan Ali wrote:
>
> On 7/23/2026 8:09 PM, Konstantin Shkolnyy wrote:
>> From: Matthew Rosato <[email protected]>
>>
>> There are a few scenarios where IOMMU replay can potentially be needed
>> for zPCI device, namely VFIO device reset scenarios where the guest
>> continues running and expects the contents of its IOMMU to be replayed
>> upon IOAT re-registration and migration scenarios where the destination
>> must reconstruct the IOMMU on the destination.
>>
>> zPCI migration is not supported yet, but the IOMMU replay function is
>> implemented so that it can be called both from IOMMUMemoryRegionClass
>> now and migration post_load later.
>>
>> Signed-off-by: Matthew Rosato <[email protected]>
>> Signed-off-by: Konstantin Shkolnyy <[email protected]>
>> ---
>> hw/s390x/s390-pci-bus.c | 62 ++++++++++++++++++++++++++++----
>> hw/s390x/s390-pci-inst.c | 4 +--
>> include/hw/s390x/s390-pci-inst.h | 1 +
>> 3 files changed, 59 insertions(+), 8 deletions(-)
>>
>> diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
>> index eff980fdfe..511926c151 100644
>> --- a/hw/s390x/s390-pci-bus.c
>> +++ b/hw/s390x/s390-pci-bus.c
>> @@ -593,14 +593,64 @@ err:
>> return ret;
>> }
>> -static void s390_pci_iommu_replay(IOMMUMemoryRegion *iommu,
>> +static void s390_pci_ioat_replay(S390PCIIOMMU *iommu)
>> +{
>> + S390IOTLBEntry entry;
>> + uint16_t error = 0;
>> + uint32_t dma_avail;
>> + hwaddr curr, end;
>> +
>> + curr = iommu->pba;
>> + end = iommu->pal;
>> +
>> + if (iommu->dm_mr) {
>> + /* If direct mapping is used, there are no guest tables to
>> replay */
>> + return;
>> + }
>> +
>> + if (iommu->dma_limit) {
>> + dma_avail = iommu->dma_limit->avail;
>> + } else {
>> + dma_avail = 1;
>> + }
>> +
>> + while (curr < end) {
>> + error = s390_guest_io_table_walk(iommu->g_iota, curr, &entry);
>> + if (error) {
>> + pbdev->state = ZPCI_FS_ERROR;
>
> This patch doesn't compile on its own. Trying to compile with just this
> patch gives the error:
>
> i-bus.c.o -c ../hw/s390x/s390-pci-bus.c
> ../hw/s390x/s390-pci-bus.c: In function ‘s390_pci_ioat_replay’:
> ../hw/s390x/s390-pci-bus.c:620:13: error: ‘pbdev’ undeclared (first use
> in this function)
> 620 | pbdev->state = ZPCI_FS_ERROR;
> | ^~~~~
> ../hw/s390x/s390-pci-bus.c:620:13: note: each undeclared identifier is
> reported only once for each function it appears in
>
> This should be fixed to avoid breaking git bisectability.
>
Oh, thanks for pointing this out. Not sure what happened here, I
thought I wrote the new version and tested it independent of this
series, but maybe I did it on top where we get pbdev as an input to
s390_pci_ioat_replay() and then botched the rebase. That sounds most
likely, but I can't find my working branch at this point.
In any event, doing a S390PCIBusDevice *pbdev = iommu->pbdev; upfront
would be the most straightforward solution, and then it will go away in
patch 3 to instead be replaced by S390PCIIOMMU *iommu = pbdev->iommu;
Konstantin, I can send you another version or you can do that yourself,
up to you.
Here's a diff against this patch of what I mean, with a little extra
defensive programming:
diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index 511926c151..21bca4d787 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -595,6 +595,7 @@ err:
static void s390_pci_ioat_replay(S390PCIIOMMU *iommu)
{
+ S390PCIBusDevice *pbdev = iommu->pbdev;
S390IOTLBEntry entry;
uint16_t error = 0;
uint32_t dma_avail;
@@ -603,7 +604,7 @@ static void s390_pci_ioat_replay(S390PCIIOMMU *iommu)
curr = iommu->pba;
end = iommu->pal;
- if (iommu->dm_mr) {
+ if (iommu->dm_mr || !pbdev) {
/* If direct mapping is used, there are no guest tables to
replay */
return;
}
