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envelope-from=kshk@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Because S390PCIIOMMU has just been cleaned up of fields it didn't have to carry, add a comment explaining why it exists in the first place and discouraging adding more fields to it in the future. Signed-off-by: Konstantin Shkolnyy --- include/hw/s390x/s390-pci-bus.h | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/include/hw/s390x/s390-pci-bus.h b/include/hw/s390x/s390-pci-bus.h index e3cbee2695..17ecf3e0da 100644 --- a/include/hw/s390x/s390-pci-bus.h +++ b/include/hw/s390x/s390-pci-bus.h @@ -271,6 +271,17 @@ typedef struct S390PCIDMACount { QTAILQ_ENTRY(S390PCIDMACount) link; } S390PCIDMACount; +/* + * This structure holds the PCI device AddressSpace that QEMU needs to link + * into its internal structures before the zPCI and PCI devices are fully + * initialized. QEMU wants to have this "root" AddressSpace before the PCI + * device is plugged in. It's only actually used for I/O while the PCI + * device is plugged in and configured by the guest, at which time it has + * additional memory subregions from zPCI device, that can do real work. + * In other words, S390PCIIOMMU holds fields that logically belong to + * S390PCIBusDevice but need to exist before S390PCIBusDevice exists. + * Therefore, no other kind of fields should be placed in S390PCIIOMMU. + */ struct S390PCIIOMMU { Object parent_obj; AddressSpace as; -- 2.34.1