path: root/drivers/hv/channel.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2009, Microsoft Corporation.
 *
 * Authors:
 *   Haiyang Zhang <haiyangz@microsoft.com>
 *   Hank Janssen  <hjanssen@microsoft.com>
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/wait.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/hyperv.h>
#include <linux/uio.h>
#include <linux/interrupt.h>
#include <linux/set_memory.h>
#include <asm/page.h>
#include <asm/mshyperv.h>

#include "hyperv_vmbus.h"

/*
 * hv_gpadl_size - Return the real size of a gpadl, the size that Hyper-V uses
 *
 * For BUFFER gpadl, Hyper-V uses the exact same size as the guest does.
 *
 * For RING gpadl, in each ring, the guest uses one PAGE_SIZE as the header
 * (because of the alignment requirement), however, the hypervisor only
 * uses the first HV_HYP_PAGE_SIZE as the header, therefore leaving a
 * (PAGE_SIZE - HV_HYP_PAGE_SIZE) gap. And since there are two rings in a
 * ringbuffer, the total size for a RING gpadl that Hyper-V uses is the
 * total size that the guest uses minus twice of the gap size.
 */
static inline u32 hv_gpadl_size(enum hv_gpadl_type type, u32 size)
{
	switch (type) {
	case HV_GPADL_BUFFER:
		return size;
	case HV_GPADL_RING:
		/* The size of a ringbuffer must be page-aligned */
		BUG_ON(size % PAGE_SIZE);
		/*
		 * Two things to notice here:
		 * 1) We're processing two ring buffers as a unit
		 * 2) We're skipping any space larger than HV_HYP_PAGE_SIZE in
		 * the first guest-size page of each of the two ring buffers.
		 * So we effectively subtract out two guest-size pages, and add
		 * back two Hyper-V size pages.
		 */
		return size - 2 * (PAGE_SIZE - HV_HYP_PAGE_SIZE);
	}
	BUG();
	return 0;
}

/*
 * hv_ring_gpadl_send_hvpgoffset - Calculate the send offset (in unit of
 *                                 HV_HYP_PAGE) in a ring gpadl based on the
 *                                 offset in the guest
 *
 * @offset: the offset (in bytes) where the send ringbuffer starts in the
 *               virtual address space of the guest
 */
static inline u32 hv_ring_gpadl_send_hvpgoffset(u32 offset)
{

	/*
	 * For RING gpadl, in each ring, the guest uses one PAGE_SIZE as the
	 * header (because of the alignment requirement), however, the
	 * hypervisor only uses the first HV_HYP_PAGE_SIZE as the header,
	 * therefore leaving a (PAGE_SIZE - HV_HYP_PAGE_SIZE) gap.
	 *
	 * And to calculate the effective send offset in gpadl, we need to
	 * substract this gap.
	 */
	return (offset - (PAGE_SIZE - HV_HYP_PAGE_SIZE)) >> HV_HYP_PAGE_SHIFT;
}

/*
 * hv_gpadl_hvpfn - Return the Hyper-V page PFN of the @i th Hyper-V page in
 *                  the gpadl
 *
 * @type: the type of the gpadl
 * @kbuffer: the pointer to the gpadl in the guest
 * @size: the total size (in bytes) of the gpadl
 * @send_offset: the offset (in bytes) where the send ringbuffer starts in the
 *               virtual address space of the guest
 * @i: the index
 */
static inline u64 hv_gpadl_hvpfn(enum hv_gpadl_type type, void *kbuffer,
				 u32 size, u32 send_offset, int i)
{
	int send_idx = hv_ring_gpadl_send_hvpgoffset(send_offset);
	unsigned long delta = 0UL;

	switch (type) {
	case HV_GPADL_BUFFER:
		break;
	case HV_GPADL_RING:
		if (i == 0)
			delta = 0;
		else if (i <= send_idx)
			delta = PAGE_SIZE - HV_HYP_PAGE_SIZE;
		else
			delta = 2 * (PAGE_SIZE - HV_HYP_PAGE_SIZE);
		break;
	default:
		BUG();