[RFC 6/8] s390x/pci: Handle devices that support relaxed alignment

[Matthew Rosato]

Certain zPCI device types (e.g. ISM) allow for a different set of address
alignment rules for PCISTB instructions.  Recognize this distinction and
perform only a subset of alignment checks for intercepted PCISTB
instructions.

Signed-off-by: Matthew Rosato <mjros...@linux.ibm.com>
---
 hw/s390x/s390-pci-inst.c        | 34 ++++++++++++++++++++--------------
 hw/s390x/s390-pci-vfio.c        |  3 +++
 include/hw/s390x/s390-pci-clp.h |  1 +
 3 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/hw/s390x/s390-pci-inst.c b/hw/s390x/s390-pci-inst.c
index a5270d0..30698e5 100644
--- a/hw/s390x/s390-pci-inst.c
+++ b/hw/s390x/s390-pci-inst.c
@@ -868,25 +868,31 @@ int pcistb_service_call(S390CPU *cpu, uint8_t r1, uint8_t 
r3, uint64_t gaddr,
         return 0;
     }
 
-    /* Verify the address, offset and length */
-    /* offset must be a multiple of 8 */
-    if (offset % 8) {
-        goto specification_error;
-    }
-    /* Length must be greater than 8, a multiple of 8 */
-    /* and not greater than maxstbl */
-    if ((len <= 8) || (len % 8) ||
-        (len > pbdev->pci_group->zpci_group.maxstbl)) {
-        goto specification_error;
+    /*
+     * If the specified device supports relaxed alignment, some checks can
+     * be skipped.
+     */
+    if (!(pbdev->pci_group->zpci_group.fr & CLP_RSP_QPCIG_MASK_RELAXED)) {
+        /* Verify the address, offset and length */
+        /* offset must be a multiple of 8 */
+        if (offset % 8) {
+            goto specification_error;
+        }
+        /* Length must be greater than 8, a multiple of 8 */
+        /* and not greater than maxstbl */
+        if ((len <= 8) || (len % 8) ||
+            (len > pbdev->pci_group->zpci_group.maxstbl)) {
+            goto specification_error;
+        }
+        /* Guest address must be double word aligned */
+        if (gaddr & 0x07UL) {
+            goto specification_error;
+        }
     }
     /* Do not cross a 4K-byte boundary */
     if (((offset & 0xfff) + len) > 0x1000) {
         goto specification_error;
     }
-    /* Guest address must be double word aligned */
-    if (gaddr & 0x07UL) {
-        goto specification_error;
-    }
 
     ret = pbdev->ops.pcistb(pbdev, cpu, gaddr, ar, pcias, len, offset);
 
diff --git a/hw/s390x/s390-pci-vfio.c b/hw/s390x/s390-pci-vfio.c
index 9296e1b..9439fe1 100644
--- a/hw/s390x/s390-pci-vfio.c
+++ b/hw/s390x/s390-pci-vfio.c
@@ -156,6 +156,9 @@ static void s390_pci_read_group(S390PCIBusDevice *pbdev,
         if (cap->flags & VFIO_DEVICE_INFO_ZPCI_FLAG_REFRESH) {
             resgrp->fr = 1;
         }
+        if (cap->flags & VFIO_DEVICE_INFO_ZPCI_FLAG_RELAXED) {
+            resgrp->fr |= CLP_RSP_QPCIG_MASK_RELAXED;
+        }
         resgrp->dasm = cap->dasm;
         resgrp->msia = cap->msi_addr;
         resgrp->mui = cap->mui;
diff --git a/include/hw/s390x/s390-pci-clp.h b/include/hw/s390x/s390-pci-clp.h
index 96b8e3f..73a28a0 100644
--- a/include/hw/s390x/s390-pci-clp.h
+++ b/include/hw/s390x/s390-pci-clp.h
@@ -158,6 +158,7 @@ typedef struct ClpRspQueryPciGrp {
 #define CLP_RSP_QPCIG_MASK_NOI 0xfff
     uint16_t i;
     uint8_t version;
+#define CLP_RSP_QPCIG_MASK_RELAXED 0x8
 #define CLP_RSP_QPCIG_MASK_FRAME   0x2
 #define CLP_RSP_QPCIG_MASK_REFRESH 0x1
     uint8_t fr;
-- 
1.8.3.1