[PATCH RFC 2/2] PCI: hv: Add vPCI device reset support

[PATCH RFC 2/2] PCI: hv: Add vPCI device reset support

[wei.liu]

From: Wei Liu <wei.liu@kernel.org>

Hyper-V vPCI protocol version 1.5 adds a RESET_DEVICE request for projected
PCI functions. Negotiate the new protocol version and issue the request
through the vPCI VMBus channel from the PCI controller reset callback.

Use the existing VMBus response path. Return -ENOTTY when the host reports
STATUS_NOT_SUPPORTED so PCI core may try another reset method.

Signed-off-by: Wei Liu <wei.liu@kernel.org>
---
 Documentation/virt/hyperv/vpci.rst  |  2 +-
 drivers/pci/controller/pci-hyperv.c | 61 +++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+), 1 deletion(-)

diff --git a/Documentation/virt/hyperv/vpci.rst b/Documentation/virt/hyperv/vpci.rst
index b65b2126ede3..6bfee7225c14 100644
--- a/Documentation/virt/hyperv/vpci.rst
+++ b/Documentation/virt/hyperv/vpci.rst
@@ -65,7 +65,7 @@ exchange messages with the vPCI VSP for the purpose of setting
 up and configuring the vPCI device in Linux.  Once the device
 is fully configured in Linux as a PCI device, the VMBus
 channel is used only if Linux changes the vCPU to be interrupted
-in the guest, or if the vPCI device is removed from
+in the guest, or if the vPCI device is reset or removed from
 the VM while the VM is running.  The ongoing operation of the
 device happens directly between the Linux device driver for
 the device and the hardware, with VMBus and the VMBus channel
diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index cfc8fa403dad..d3c0fd5e1d8e 100644
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -68,6 +68,7 @@ enum pci_protocol_version_t {
 	PCI_PROTOCOL_VERSION_1_2 = PCI_MAKE_VERSION(1, 2),	/* RS1 */
 	PCI_PROTOCOL_VERSION_1_3 = PCI_MAKE_VERSION(1, 3),	/* Vibranium */
 	PCI_PROTOCOL_VERSION_1_4 = PCI_MAKE_VERSION(1, 4),	/* WS2022 */
+	PCI_PROTOCOL_VERSION_1_5 = PCI_MAKE_VERSION(1, 5),	/* GE, device reset */
 };
 
 #define CPU_AFFINITY_ALL	-1ULL
@@ -77,6 +78,7 @@ enum pci_protocol_version_t {
  * first.
  */
 static enum pci_protocol_version_t pci_protocol_versions[] = {
+	PCI_PROTOCOL_VERSION_1_5,
 	PCI_PROTOCOL_VERSION_1_4,
 	PCI_PROTOCOL_VERSION_1_3,
 	PCI_PROTOCOL_VERSION_1_2,
@@ -90,6 +92,7 @@ static enum pci_protocol_version_t pci_protocol_versions[] = {
 #define MAX_SUPPORTED_MSI_MESSAGES 0x400
 
 #define STATUS_REVISION_MISMATCH 0xC0000059
+#define STATUS_NOT_SUPPORTED     0xC00000BB
 
 /* space for 32bit serial number as string */
 #define SLOT_NAME_SIZE 11
@@ -136,6 +139,7 @@ enum pci_message_type {
 	PCI_BUS_RELATIONS2		= PCI_MESSAGE_BASE + 0x19,
 	PCI_RESOURCES_ASSIGNED3         = PCI_MESSAGE_BASE + 0x1A,
 	PCI_CREATE_INTERRUPT_MESSAGE3   = PCI_MESSAGE_BASE + 0x1B,
+	PCI_RESET_DEVICE                = PCI_MESSAGE_BASE + 0x1C,
 	PCI_MESSAGE_MAXIMUM
 };
 
@@ -1397,10 +1401,66 @@ static int hv_pcifront_write_config(struct pci_bus *bus, unsigned int devfn,
 	return PCIBIOS_SUCCESSFUL;
 }
 
+static int hv_pcifront_reset(struct pci_dev *pdev, bool probe)
+{
+	struct hv_pcibus_device *hbus =
+		container_of(pdev->bus->sysdata, struct hv_pcibus_device, sysdata);
+	struct pci_child_message reset = {};
+	struct hv_pci_compl comp_pkt;
+	struct pci_packet pkt = {
+		.completion_func = hv_pci_generic_compl,
+		.compl_ctxt = &comp_pkt,
+	};
+	enum hv_pcibus_state state;
+	int ret;
+
+	/* Device reset was added in vPCI protocol version 1.5. */
+	if (hbus->protocol_version < PCI_PROTOCOL_VERSION_1_5)
+		return -ENOTTY;
+
+	/* Hyper-V exposes projected functions directly on the root bus. */
+	if (!pci_is_root_bus(pdev->bus))
+		return -ENOTTY;
+
+	if (probe)
+		return 0;
+
+	/* Do not take state_lock: eject holds it while removing/locking pdev. */
+	state = READ_ONCE(hbus->state);
+	if (state != hv_pcibus_probed && state != hv_pcibus_installed)
+		return -ENODEV;
+
+	init_completion(&comp_pkt.host_event);
+	reset.message_type.type = PCI_RESET_DEVICE;
+	reset.wslot.slot = devfn_to_wslot(pdev->devfn);
+
+	ret = vmbus_sendpacket(hbus->hdev->channel, &reset, sizeof(reset),
+			       (unsigned long)&pkt, VM_PKT_DATA_INBAND,
+			       VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
+	if (ret)
+		return ret;
+
+	ret = wait_for_response(hbus->hdev, &comp_pkt.host_event);
+	if (ret)
+		return ret;
+
+	if (comp_pkt.completion_status == STATUS_NOT_SUPPORTED)
+		return -ENOTTY;
+
+	if (comp_pkt.completion_status) {
+		pci_err(pdev, "Hyper-V device reset failed: %#x\n",
+			comp_pkt.completion_status);
+		return -EIO;
+	}
+
+	return 0;
+}
+
 /* PCIe operations */
 static struct pci_ops hv_pcifront_ops = {
 	.read  = hv_pcifront_read_config,
 	.write = hv_pcifront_write_config,
+	.reset = hv_pcifront_reset,
 };
 
 /*
@@ -1996,6 +2056,7 @@ static void hv_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
 		break;
 
 	case PCI_PROTOCOL_VERSION_1_4:
+	case PCI_PROTOCOL_VERSION_1_5:
 		size = hv_compose_msi_req_v3(&ctxt.int_pkts.v3,
 					cpu,
 					hpdev->desc.win_slot.slot,
-- 
2.53.0