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Re: [PATCH for-5.2] s390x/pci: fix endianness issues

From: Matthew Rosato
Subject: Re: [PATCH for-5.2] s390x/pci: fix endianness issues
Date: Tue, 17 Nov 2020 13:19:02 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.3.1

On 11/17/20 12:59 PM, Philippe Mathieu-Daudé wrote:
On 11/17/20 6:13 PM, Cornelia Huck wrote:
zPCI control blocks are big endian, we need to take care that we
do proper accesses in order not to break tcg guests on little endian

Fixes: 28dc86a07299 ("s390x/pci: use a PCI Group structure")
Fixes: 9670ee752727 ("s390x/pci: use a PCI Function structure")
Fixes: 1e7552ff5c34 ("s390x/pci: get zPCI function info from host")
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

Works for me with virtio-pci devices for tcg on x86 and s390x, and for kvm.
The vfio changes are not strictly needed; did not test them due to lack of
hardware -- testing appreciated. >>
As this fixes a regression, I want this in 5.2.

  hw/s390x/s390-pci-bus.c  | 12 ++++++------
  hw/s390x/s390-pci-inst.c |  4 ++--
  hw/s390x/s390-pci-vfio.c |  8 ++++----
  3 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c
index e0dc20ce4a56..17e64e0b1200 100644
--- a/hw/s390x/s390-pci-bus.c
+++ b/hw/s390x/s390-pci-bus.c
@@ -787,12 +787,12 @@ static void s390_pci_init_default_group(void)
static void set_pbdev_info(S390PCIBusDevice *pbdev)
-    pbdev->zpci_fn.sdma = ZPCI_SDMA_ADDR;
-    pbdev->zpci_fn.edma = ZPCI_EDMA_ADDR;
-    pbdev->zpci_fn.pchid = 0;
+    stq_p(&pbdev->zpci_fn.sdma, ZPCI_SDMA_ADDR);

"zPCI control blocks are big endian" so don't we
need the _be_ accessors? stq_be_p() etc...

I don't think this is necessary. This is only available for target s390x, which is always big endian... cpu-all.h should define stq_p as stq_be_p for example inside the #if defined(TARGET_WORDS_BIGENDIAN).

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