From 00ebc44514a67fb75a46d60e4b44614ebf91230f Mon Sep 17 00:00:00 2001 From: Jaehoon Kim Date: Fri, 6 Feb 2026 10:46:02 -0600 Subject: [PATCH] s390x/pci: Fix endianness for zPCI BAR values. During zPCI scan, BAR configuration data retrieved via CLP Query was misinterpreted due to an endianness mismatch between QEMU and the guest kernel. The guest kernel's clp_store_query_pci_fn() expects BAR values in little-endian format and converts them with le32_to_cpu(). However, QEMU was incorrectly sending them in big-endian format, not following the architecture specification. This caused incorrect bit-swapping in the kernel, leading zpci_setup_bus_resources() to perform registration checks against invalid flags, making the process ineffective. Observation values for zPCI device (NVMe passthrough): LPAR from real CLP: [ 0.865595] Resource: PCI Bus 0000:00 -> zdev->bar[0].val: 0x4 [ 0.865597] start: 0x4000000000000000 [ 0.865598] end: 0x4000000000003fff [ 0.865600] flags: 0x100200 QEMU before fix (wrong): [ 0.601083] Resource: PCI Bus 0001:00 -> zdev->bar[0].val: 0x4000000 [ 0.601085] start: 0x4003000000000000 [ 0.601086] end: 0x4003000000003fff [ 0.601087] flags: 0x200 QEMU after fix (correct): [ 0.601116] Resource: PCI Bus 0001:00 -> zdev->bar[0].val: 0x4 [ 0.601117] start: 0x4003000000000000 [ 0.601118] end: 0x4003000000003fff [ 0.601119] flags: 0x100200 Signed-off-by: Jaehoon Kim Reviewed-by: Matthew Rosato Reviewed-by: Farhan Ali Reviewed-by: Eric Farman Message-ID: <20260206164645.1845366-1-jhkim@linux.ibm.com> Signed-off-by: Thomas Huth --- hw/s390x/s390-pci-inst.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c index 6b67c3c109..10066ca618 100644 --- a/hw/s390x/s390-pci-inst.c +++ b/hw/s390x/s390-pci-inst.c @@ -307,7 +307,7 @@ int clp_service_call(S390CPU *cpu, uint8_t r2, uintptr_t ra) uint32_t data = pci_get_long(pbdev->pdev->config + PCI_BASE_ADDRESS_0 + (i * 4)); - stl_be_p(&resquery->bar[i], data); + stl_le_p(&resquery->bar[i], data); resquery->bar_size[i] = pbdev->pdev->io_regions[i].size ? ctz64(pbdev->pdev->io_regions[i].size) : 0; trace_s390_pci_bar(i,