![Olaf Hering](/assets/img/avatar_default.png)
All channel interrupts are bound to specific VCPUs in the guest at the point channel is created. While currently, we invoke the polling function on the correct CPU (the CPU to which the channel is bound to) in some cases we may run the polling function in a non-interrupt context. This potentially can cause an issue as the polling function can be interrupted by the channel callback function. Fix the issue by running the polling function on the appropriate CPU at interrupt level. Additional details of the issue being addressed by this patch are given below: Currently hv_fcopy_onchannelcallback is called from interrupts and also via the ->write function of hv_utils. Since the used global variables to maintain state are not thread safe the state can get out of sync. This affects the variable state as well as the channel inbound buffer. As suggested by KY adjust hv_poll_channel to always run the given callback on the cpu which the channel is bound to. This avoids the need for locking because all the util services are single threaded and only one transaction is active at any given point in time. Additionally, remove the context variable, they will always be the same as recv_channel. Signed-off-by: Olaf Hering <olaf@aepfle.de> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
343 lines
9.5 KiB
C
343 lines
9.5 KiB
C
/*
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* An implementation of file copy service.
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*
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* Copyright (C) 2014, Microsoft, Inc.
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*
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* Author : K. Y. Srinivasan <ksrinivasan@novell.com>
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published
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* by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
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* NON INFRINGEMENT. See the GNU General Public License for more
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* details.
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*
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/nls.h>
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#include <linux/workqueue.h>
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#include <linux/hyperv.h>
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#include <linux/sched.h>
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#include "hyperv_vmbus.h"
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#include "hv_utils_transport.h"
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#define WIN8_SRV_MAJOR 1
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#define WIN8_SRV_MINOR 1
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#define WIN8_SRV_VERSION (WIN8_SRV_MAJOR << 16 | WIN8_SRV_MINOR)
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/*
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* Global state maintained for transaction that is being processed.
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* For a class of integration services, including the "file copy service",
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* the specified protocol is a "request/response" protocol which means that
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* there can only be single outstanding transaction from the host at any
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* given point in time. We use this to simplify memory management in this
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* driver - we cache and process only one message at a time.
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*
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* While the request/response protocol is guaranteed by the host, we further
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* ensure this by serializing packet processing in this driver - we do not
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* read additional packets from the VMBUs until the current packet is fully
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* handled.
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*/
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static struct {
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int state; /* hvutil_device_state */
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int recv_len; /* number of bytes received. */
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struct hv_fcopy_hdr *fcopy_msg; /* current message */
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struct vmbus_channel *recv_channel; /* chn we got the request */
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u64 recv_req_id; /* request ID. */
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} fcopy_transaction;
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static void fcopy_respond_to_host(int error);
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static void fcopy_send_data(struct work_struct *dummy);
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static void fcopy_timeout_func(struct work_struct *dummy);
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static DECLARE_DELAYED_WORK(fcopy_timeout_work, fcopy_timeout_func);
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static DECLARE_WORK(fcopy_send_work, fcopy_send_data);
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static const char fcopy_devname[] = "vmbus/hv_fcopy";
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static u8 *recv_buffer;
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static struct hvutil_transport *hvt;
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/*
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* This state maintains the version number registered by the daemon.
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*/
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static int dm_reg_value;
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static void fcopy_poll_wrapper(void *channel)
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{
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/* Transaction is finished, reset the state here to avoid races. */
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fcopy_transaction.state = HVUTIL_READY;
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hv_fcopy_onchannelcallback(channel);
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}
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static void fcopy_timeout_func(struct work_struct *dummy)
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{
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/*
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* If the timer fires, the user-mode component has not responded;
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* process the pending transaction.
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*/
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fcopy_respond_to_host(HV_E_FAIL);
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hv_poll_channel(fcopy_transaction.recv_channel, fcopy_poll_wrapper);
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}
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static int fcopy_handle_handshake(u32 version)
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{
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u32 our_ver = FCOPY_CURRENT_VERSION;
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switch (version) {
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case FCOPY_VERSION_0:
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/* Daemon doesn't expect us to reply */
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dm_reg_value = version;
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break;
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case FCOPY_VERSION_1:
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/* Daemon expects us to reply with our own version */
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if (hvutil_transport_send(hvt, &our_ver, sizeof(our_ver)))
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return -EFAULT;
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dm_reg_value = version;
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break;
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default:
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/*
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* For now we will fail the registration.
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* If and when we have multiple versions to
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* deal with, we will be backward compatible.
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* We will add this code when needed.
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*/
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return -EINVAL;
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}
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pr_debug("FCP: userspace daemon ver. %d registered\n", version);
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hv_poll_channel(fcopy_transaction.recv_channel, fcopy_poll_wrapper);
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return 0;
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}
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static void fcopy_send_data(struct work_struct *dummy)
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{
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struct hv_start_fcopy *smsg_out = NULL;
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int operation = fcopy_transaction.fcopy_msg->operation;
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struct hv_start_fcopy *smsg_in;
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void *out_src;
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int rc, out_len;
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/*
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* The strings sent from the host are encoded in
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* in utf16; convert it to utf8 strings.
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* The host assures us that the utf16 strings will not exceed
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* the max lengths specified. We will however, reserve room
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* for the string terminating character - in the utf16s_utf8s()
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* function we limit the size of the buffer where the converted
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* string is placed to W_MAX_PATH -1 to guarantee
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* that the strings can be properly terminated!
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*/
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switch (operation) {
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case START_FILE_COPY:
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out_len = sizeof(struct hv_start_fcopy);
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smsg_out = kzalloc(sizeof(*smsg_out), GFP_KERNEL);
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if (!smsg_out)
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return;
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smsg_out->hdr.operation = operation;
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smsg_in = (struct hv_start_fcopy *)fcopy_transaction.fcopy_msg;
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utf16s_to_utf8s((wchar_t *)smsg_in->file_name, W_MAX_PATH,
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UTF16_LITTLE_ENDIAN,
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(__u8 *)&smsg_out->file_name, W_MAX_PATH - 1);
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utf16s_to_utf8s((wchar_t *)smsg_in->path_name, W_MAX_PATH,
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UTF16_LITTLE_ENDIAN,
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(__u8 *)&smsg_out->path_name, W_MAX_PATH - 1);
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smsg_out->copy_flags = smsg_in->copy_flags;
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smsg_out->file_size = smsg_in->file_size;
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out_src = smsg_out;
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break;
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default:
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out_src = fcopy_transaction.fcopy_msg;
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out_len = fcopy_transaction.recv_len;
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break;
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}
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fcopy_transaction.state = HVUTIL_USERSPACE_REQ;
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rc = hvutil_transport_send(hvt, out_src, out_len);
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if (rc) {
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pr_debug("FCP: failed to communicate to the daemon: %d\n", rc);
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if (cancel_delayed_work_sync(&fcopy_timeout_work)) {
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fcopy_respond_to_host(HV_E_FAIL);
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fcopy_transaction.state = HVUTIL_READY;
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}
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}
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kfree(smsg_out);
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return;
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}
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/*
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* Send a response back to the host.
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*/
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static void
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fcopy_respond_to_host(int error)
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{
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struct icmsg_hdr *icmsghdr;
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u32 buf_len;
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struct vmbus_channel *channel;
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u64 req_id;
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/*
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* Copy the global state for completing the transaction. Note that
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* only one transaction can be active at a time. This is guaranteed
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* by the file copy protocol implemented by the host. Furthermore,
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* the "transaction active" state we maintain ensures that there can
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* only be one active transaction at a time.
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*/
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buf_len = fcopy_transaction.recv_len;
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channel = fcopy_transaction.recv_channel;
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req_id = fcopy_transaction.recv_req_id;
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icmsghdr = (struct icmsg_hdr *)
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&recv_buffer[sizeof(struct vmbuspipe_hdr)];
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if (channel->onchannel_callback == NULL)
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/*
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* We have raced with util driver being unloaded;
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* silently return.
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*/
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return;
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icmsghdr->status = error;
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icmsghdr->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
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vmbus_sendpacket(channel, recv_buffer, buf_len, req_id,
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VM_PKT_DATA_INBAND, 0);
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}
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void hv_fcopy_onchannelcallback(void *context)
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{
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struct vmbus_channel *channel = context;
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u32 recvlen;
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u64 requestid;
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struct hv_fcopy_hdr *fcopy_msg;
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struct icmsg_hdr *icmsghdr;
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struct icmsg_negotiate *negop = NULL;
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int util_fw_version;
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int fcopy_srv_version;
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if (fcopy_transaction.state > HVUTIL_READY)
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return;
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vmbus_recvpacket(channel, recv_buffer, PAGE_SIZE * 2, &recvlen,
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&requestid);
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if (recvlen <= 0)
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return;
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icmsghdr = (struct icmsg_hdr *)&recv_buffer[
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sizeof(struct vmbuspipe_hdr)];
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if (icmsghdr->icmsgtype == ICMSGTYPE_NEGOTIATE) {
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util_fw_version = UTIL_FW_VERSION;
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fcopy_srv_version = WIN8_SRV_VERSION;
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vmbus_prep_negotiate_resp(icmsghdr, negop, recv_buffer,
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util_fw_version, fcopy_srv_version);
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} else {
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fcopy_msg = (struct hv_fcopy_hdr *)&recv_buffer[
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sizeof(struct vmbuspipe_hdr) +
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sizeof(struct icmsg_hdr)];
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/*
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* Stash away this global state for completing the
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* transaction; note transactions are serialized.
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*/
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fcopy_transaction.recv_len = recvlen;
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fcopy_transaction.recv_channel = channel;
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fcopy_transaction.recv_req_id = requestid;
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fcopy_transaction.fcopy_msg = fcopy_msg;
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if (fcopy_transaction.state < HVUTIL_READY) {
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/* Userspace is not registered yet */
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fcopy_respond_to_host(HV_E_FAIL);
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return;
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}
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fcopy_transaction.state = HVUTIL_HOSTMSG_RECEIVED;
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/*
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* Send the information to the user-level daemon.
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*/
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schedule_work(&fcopy_send_work);
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schedule_delayed_work(&fcopy_timeout_work,
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HV_UTIL_TIMEOUT * HZ);
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return;
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}
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icmsghdr->icflags = ICMSGHDRFLAG_TRANSACTION | ICMSGHDRFLAG_RESPONSE;
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vmbus_sendpacket(channel, recv_buffer, recvlen, requestid,
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VM_PKT_DATA_INBAND, 0);
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}
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/* Callback when data is received from userspace */
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static int fcopy_on_msg(void *msg, int len)
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{
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int *val = (int *)msg;
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if (len != sizeof(int))
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return -EINVAL;
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if (fcopy_transaction.state == HVUTIL_DEVICE_INIT)
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return fcopy_handle_handshake(*val);
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if (fcopy_transaction.state != HVUTIL_USERSPACE_REQ)
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return -EINVAL;
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/*
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* Complete the transaction by forwarding the result
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* to the host. But first, cancel the timeout.
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*/
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if (cancel_delayed_work_sync(&fcopy_timeout_work)) {
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fcopy_transaction.state = HVUTIL_USERSPACE_RECV;
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fcopy_respond_to_host(*val);
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hv_poll_channel(fcopy_transaction.recv_channel,
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fcopy_poll_wrapper);
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}
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return 0;
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}
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static void fcopy_on_reset(void)
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{
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/*
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* The daemon has exited; reset the state.
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*/
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fcopy_transaction.state = HVUTIL_DEVICE_INIT;
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if (cancel_delayed_work_sync(&fcopy_timeout_work))
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fcopy_respond_to_host(HV_E_FAIL);
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}
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int hv_fcopy_init(struct hv_util_service *srv)
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{
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recv_buffer = srv->recv_buffer;
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/*
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* When this driver loads, the user level daemon that
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* processes the host requests may not yet be running.
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* Defer processing channel callbacks until the daemon
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* has registered.
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*/
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fcopy_transaction.state = HVUTIL_DEVICE_INIT;
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hvt = hvutil_transport_init(fcopy_devname, 0, 0,
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fcopy_on_msg, fcopy_on_reset);
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if (!hvt)
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return -EFAULT;
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return 0;
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}
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void hv_fcopy_deinit(void)
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{
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fcopy_transaction.state = HVUTIL_DEVICE_DYING;
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cancel_delayed_work_sync(&fcopy_timeout_work);
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hvutil_transport_destroy(hvt);
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}
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