Merge tag 'hyperv-next-signed-20250602' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux

Pull hyperv updates from Wei Liu:

 - Support for Virtual Trust Level (VTL) on arm64 (Roman Kisel)

 - Fixes for Hyper-V UIO driver (Long Li)

 - Fixes for Hyper-V PCI driver (Michael Kelley)

 - Select CONFIG_SYSFB for Hyper-V guests (Michael Kelley)

 - Documentation updates for Hyper-V VMBus (Michael Kelley)

 - Enhance logging for hv_kvp_daemon (Shradha Gupta)

* tag 'hyperv-next-signed-20250602' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux: (23 commits)
  Drivers: hv: Always select CONFIG_SYSFB for Hyper-V guests
  Drivers: hv: vmbus: Add comments about races with "channels" sysfs dir
  Documentation: hyperv: Update VMBus doc with new features and info
  PCI: hv: Remove unnecessary flex array in struct pci_packet
  Drivers: hv: Remove hv_alloc/free_* helpers
  Drivers: hv: Use kzalloc for panic page allocation
  uio_hv_generic: Align ring size to system page
  uio_hv_generic: Use correct size for interrupt and monitor pages
  Drivers: hv: Allocate interrupt and monitor pages aligned to system page boundary
  arch/x86: Provide the CPU number in the wakeup AP callback
  x86/hyperv: Fix APIC ID and VP index confusion in hv_snp_boot_ap()
  PCI: hv: Get vPCI MSI IRQ domain from DeviceTree
  ACPI: irq: Introduce acpi_get_gsi_dispatcher()
  Drivers: hv: vmbus: Introduce hv_get_vmbus_root_device()
  Drivers: hv: vmbus: Get the IRQ number from DeviceTree
  dt-bindings: microsoft,vmbus: Add interrupt and DMA coherence properties
  arm64, x86: hyperv: Report the VTL the system boots in
  arm64: hyperv: Initialize the Virtual Trust Level field
  Drivers: hv: Provide arch-neutral implementation of get_vtl()
  Drivers: hv: Enable VTL mode for arm64
  ...

2 files changed, 38 insertions, 6 deletions

diff --git a/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml b/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml
index a8d40c766dcd..0bea4f5287ce 100644
--- a/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml
+++ b/Documentation/devicetree/bindings/bus/microsoft,vmbus.yaml
@@ -10,8 +10,8 @@ maintainers:
   - Saurabh Sengar <ssengar@linux.microsoft.com>
 
 description:
-  VMBus is a software bus that implement the protocols for communication
-  between the root or host OS and guest OSs (virtual machines).
+  VMBus is a software bus that implements the protocols for communication
+  between the root or host OS and guest OS'es (virtual machines).
 
 properties:
   compatible:
@@ -25,9 +25,16 @@ properties:
   '#size-cells':
     const: 1
 
+  dma-coherent: true
+
+  interrupts:
+    maxItems: 1
+    description: Interrupt is used to report a message from the host.
+
 required:
   - compatible
   - ranges
+  - interrupts
   - '#address-cells'
   - '#size-cells'
 
@@ -35,6 +42,8 @@ additionalProperties: false
 
 examples:
   - |
+    #include <dt-bindings/interrupt-controller/irq.h>
+    #include <dt-bindings/interrupt-controller/arm-gic.h>
     soc {
         #address-cells = <2>;
         #size-cells = <1>;
@@ -49,6 +58,9 @@ examples:
                 #address-cells = <2>;
                 #size-cells = <1>;
                 ranges = <0x0f 0xf0000000 0x0f 0xf0000000 0x10000000>;
+                dma-coherent;
+                interrupt-parent = <&gic>;
+                interrupts = <GIC_PPI 2 IRQ_TYPE_EDGE_RISING>;
             };
         };
     };
diff --git a/Documentation/virt/hyperv/vmbus.rst b/Documentation/virt/hyperv/vmbus.rst
index 1dcef6a7fda3..654bb4849972 100644
--- a/Documentation/virt/hyperv/vmbus.rst
+++ b/Documentation/virt/hyperv/vmbus.rst
@@ -250,10 +250,18 @@ interrupts are not Linux IRQs, there are no entries in /proc/interrupts
 or /proc/irq corresponding to individual VMBus channel interrupts.
 
 An online CPU in a Linux guest may not be taken offline if it has
-VMBus channel interrupts assigned to it.  Any such channel
-interrupts must first be manually reassigned to another CPU as
-described above.  When no channel interrupts are assigned to the
-CPU, it can be taken offline.
+VMBus channel interrupts assigned to it. Starting in kernel v6.15,
+any such interrupts are automatically reassigned to some other CPU
+at the time of offlining. The "other" CPU is chosen by the
+implementation and is not load balanced or otherwise intelligently
+determined. If the CPU is onlined again, channel interrupts previously
+assigned to it are not moved back. As a result, after multiple CPUs
+have been offlined, and perhaps onlined again, the interrupt-to-CPU
+mapping may be scrambled and non-optimal. In such a case, optimal
+assignments must be re-established manually. For kernels v6.14 and
+earlier, any conflicting channel interrupts must first be manually
+reassigned to another CPU as described above. Then when no channel
+interrupts are assigned to the CPU, it can be taken offline.
 
 The VMBus channel interrupt handling code is designed to work
 correctly even if an interrupt is received on a CPU other than the
@@ -324,3 +332,15 @@ rescinded, neither Hyper-V nor Linux retains any state about
 its previous existence. Such a device might be re-added later,
 in which case it is treated as an entirely new device. See
 vmbus_onoffer_rescind().
+
+For some devices, such as the KVP device, Hyper-V automatically
+sends a rescind message when the primary channel is closed,
+likely as a result of unbinding the device from its driver.
+The rescind causes Linux to remove the device. But then Hyper-V
+immediately reoffers the device to the guest, causing a new
+instance of the device to be created in Linux. For other
+devices, such as the synthetic SCSI and NIC devices, closing the
+primary channel does *not* result in Hyper-V sending a rescind
+message. The device continues to exist in Linux on the VMBus,
+but with no driver bound to it. The same driver or a new driver
+can subsequently be bound to the existing instance of the device.