Remove old lguest I/O infrrasructure.

This patch gets rid of the old lguest host I/O infrastructure and
replaces it with a single hypercall "LHCALL_NOTIFY" which takes an
address.

The main change is the removal of io.c: that mainly did inter-guest
I/O, which virtio doesn't yet support.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/lguest/Makefile

 # Host requires the other files, which can be a module.
 obj-$(CONFIG_LGUEST)	+= lg.o
 lg-y = core.o hypercalls.o page_tables.o interrupts_and_traps.o \
-	segments.o io.o lguest_user.o
+	segments.o lguest_user.o
 
 lg-$(CONFIG_X86_32) += x86/switcher_32.o x86/core.o
 

drivers/lguest/core.c

@@ -202,13 +202,12 @@ int run_guest(struct lguest *lg, unsigned long __user *user)
 		if (lg->hcall)
 			do_hypercalls(lg);
 
-		/* It's possible the Guest did a SEND_DMA hypercall to the
+		/* It's possible the Guest did a NOTIFY hypercall to the
 		 * Launcher, in which case we return from the read() now. */
-		if (lg->dma_is_pending) {
-			if (put_user(lg->pending_dma, user) ||
-			    put_user(lg->pending_key, user+1))
+		if (lg->pending_notify) {
+			if (put_user(lg->pending_notify, user))
 				return -EFAULT;
-			return sizeof(unsigned long)*2;
+			return sizeof(lg->pending_notify);
 		}
 
 		/* Check for signals */
@@ -288,9 +287,6 @@ static int __init init(void)
 	if (err)
 		goto unmap;
 
-	/* The I/O subsystem needs some things initialized. */
-	lguest_io_init();
-
 	/* We might need to reserve an interrupt vector. */
 	err = init_interrupts();
 	if (err)

drivers/lguest/hypercalls.c

@@ -60,22 +60,9 @@ static void do_hcall(struct lguest *lg, struct hcall_args *args)
 		else
 			guest_pagetable_flush_user(lg);
 		break;
-	case LHCALL_BIND_DMA:
-		/* BIND_DMA really wants four arguments, but it's the only call
-		 * which does.  So the Guest packs the number of buffers and
-		 * the interrupt number into the final argument, and we decode
-		 * it here.  This can legitimately fail, since we currently
-		 * place a limit on the number of DMA pools a Guest can have.
-		 * So we return true or false from this call. */
-		args->arg0 = bind_dma(lg, args->arg1, args->arg2,
-				     args->arg3 >> 8, args->arg3 & 0xFF);
-		break;
 
 	/* All these calls simply pass the arguments through to the right
 	 * routines. */
-	case LHCALL_SEND_DMA:
-		send_dma(lg, args->arg1, args->arg2);
-		break;
 	case LHCALL_NEW_PGTABLE:
 		guest_new_pagetable(lg, args->arg1);
 		break;
@@ -99,6 +86,9 @@ static void do_hcall(struct lguest *lg, struct hcall_args *args)
 		/* Similarly, this sets the halted flag for run_guest(). */
 		lg->halted = 1;
 		break;
+	case LHCALL_NOTIFY:
+		lg->pending_notify = args->arg1;
+		break;
 	default:
 		if (lguest_arch_do_hcall(lg, args))
 			kill_guest(lg, "Bad hypercall %li\n", args->arg0);
@@ -156,9 +146,9 @@ static void do_async_hcalls(struct lguest *lg)
 			break;
 		}
 
- 		/* Stop doing hypercalls if we've just done a DMA to the
-		 * Launcher: it needs to service this first. */
-		if (lg->dma_is_pending)
+		/* Stop doing hypercalls if they want to notify the Launcher:
+		 * it needs to service this first. */
+		if (lg->pending_notify)
 			break;
 	}
 }
@@ -220,9 +210,9 @@ void do_hypercalls(struct lguest *lg)
 	do_async_hcalls(lg);
 
 	/* If we stopped reading the hypercall ring because the Guest did a
-	 * SEND_DMA to the Launcher, we want to return now.  Otherwise we do
+	 * NOTIFY to the Launcher, we want to return now.  Otherwise we do
 	 * the hypercall. */
-	if (!lg->dma_is_pending) {
+	if (!lg->pending_notify) {
 		do_hcall(lg, lg->hcall);
 		/* Tricky point: we reset the hcall pointer to mark the
 		 * hypercall as "done".  We use the hcall pointer rather than

drivers/lguest/lg.h

@@ -5,7 +5,6 @@
 #include <linux/types.h>
 #include <linux/init.h>
 #include <linux/stringify.h>
-#include <linux/futex.h>
 #include <linux/lguest.h>
 #include <linux/lguest_launcher.h>
 #include <linux/wait.h>
@@ -17,17 +16,6 @@
 void free_pagetables(void);
 int init_pagetables(struct page **switcher_page, unsigned int pages);
 
-struct lguest_dma_info
-{
-	struct list_head list;
-	union futex_key key;
-	unsigned long dmas;
-	struct lguest *owner;
-	u16 next_dma;
-	u16 num_dmas;
-	u8 interrupt; 	/* 0 when not registered */
-};
-
 struct pgdir
 {
 	unsigned long gpgdir;
@@ -90,15 +78,11 @@ struct lguest
 	struct task_struct *wake;
 
 	unsigned long noirq_start, noirq_end;
-	int dma_is_pending;
-	unsigned long pending_dma; /* struct lguest_dma */
-	unsigned long pending_key; /* address they're sending to */
+	unsigned long pending_notify; /* pfn from LHCALL_NOTIFY */
 
 	unsigned int stack_pages;
 	u32 tsc_khz;
 
-	struct lguest_dma_info dma[LGUEST_MAX_DMA];
-
 	/* Dead? */
 	const char *dead;
 
@@ -184,15 +168,6 @@ extern char start_switcher_text[], end_switcher_text[], switch_to_guest[];
 int lguest_device_init(void);
 void lguest_device_remove(void);
 
-/* io.c: */
-void lguest_io_init(void);
-int bind_dma(struct lguest *lg,
-	     unsigned long key, unsigned long udma, u16 numdmas, u8 interrupt);
-void send_dma(struct lguest *info, unsigned long key, unsigned long udma);
-void release_all_dma(struct lguest *lg);
-unsigned long get_dma_buffer(struct lguest *lg, unsigned long key,
-			     unsigned long *interrupt);
-
 /* hypercalls.c: */
 void do_hypercalls(struct lguest *lg);
 void write_timestamp(struct lguest *lg);

drivers/lguest/lguest_user.c

@@ -2,37 +2,12 @@
  * controls and communicates with the Guest.  For example, the first write will
  * tell us the Guest's memory layout, pagetable, entry point and kernel address
  * offset.  A read will run the Guest until something happens, such as a signal
- * or the Guest doing a DMA out to the Launcher.  Writes are also used to get a
- * DMA buffer registered by the Guest and to send the Guest an interrupt. :*/
+ * or the Guest doing a NOTIFY out to the Launcher. :*/
 #include <linux/uaccess.h>
 #include <linux/miscdevice.h>
 #include <linux/fs.h>
 #include "lg.h"
 
-/*L:310 To send DMA into the Guest, the Launcher needs to be able to ask for a
- * DMA buffer.  This is done by writing LHREQ_GETDMA and the key to
- * /dev/lguest. */
-static long user_get_dma(struct lguest *lg, const unsigned long __user *input)
-{
-	unsigned long key, udma, irq;
-
-	/* Fetch the key they wrote to us. */
-	if (get_user(key, input) != 0)
-		return -EFAULT;
-	/* Look for a free Guest DMA buffer bound to that key. */
-	udma = get_dma_buffer(lg, key, &irq);
-	if (!udma)
-		return -ENOENT;
-
-	/* We need to tell the Launcher what interrupt the Guest expects after
-	 * the buffer is filled.  We stash it in udma->used_len. */
-	lgwrite_u32(lg, udma + offsetof(struct lguest_dma, used_len), irq);
-
-	/* The (guest-physical) address of the DMA buffer is returned from
-	 * the write(). */
-	return udma;
-}
-
 /*L:315 To force the Guest to stop running and return to the Launcher, the
  * Waker sets writes LHREQ_BREAK and the value "1" to /dev/lguest.  The
  * Launcher then writes LHREQ_BREAK and "0" to release the Waker. */
@@ -102,10 +77,10 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o)
 		return len;
 	}
 
-	/* If we returned from read() last time because the Guest sent DMA,
+	/* If we returned from read() last time because the Guest notified,
 	 * clear the flag. */
-	if (lg->dma_is_pending)
-		lg->dma_is_pending = 0;
+	if (lg->pending_notify)
+		lg->pending_notify = 0;
 
 	/* Run the Guest until something interesting happens. */
 	return run_guest(lg, (unsigned long __user *)user);
@@ -216,7 +191,7 @@ unlock:
 /*L:010 The first operation the Launcher does must be a write.  All writes
  * start with a 32 bit number: for the first write this must be
  * LHREQ_INITIALIZE to set up the Guest.  After that the Launcher can use
- * writes of other values to get DMA buffers and send interrupts. */
+ * writes of other values to send interrupts. */
 static ssize_t write(struct file *file, const char __user *in,
 		     size_t size, loff_t *off)
 {
@@ -245,8 +220,6 @@ static ssize_t write(struct file *file, const char __user *in,
 	switch (req) {
 	case LHREQ_INITIALIZE:
 		return initialize(file, input);
-	case LHREQ_GETDMA:
-		return user_get_dma(lg, input);
 	case LHREQ_IRQ:
 		return user_send_irq(lg, input);
 	case LHREQ_BREAK:
@@ -276,8 +249,6 @@ static int close(struct inode *inode, struct file *file)
 	mutex_lock(&lguest_lock);
 	/* Cancels the hrtimer set via LHCALL_SET_CLOCKEVENT. */
 	hrtimer_cancel(&lg->hrt);
-	/* Free any DMA buffers the Guest had bound. */
-	release_all_dma(lg);
 	/* Free up the shadow page tables for the Guest. */
 	free_guest_pagetable(lg);
 	/* Now all the memory cleanups are done, it's safe to release the

include/asm-x86/lguest_hcall.h

@@ -13,11 +13,10 @@
 #define LHCALL_TS		8
 #define LHCALL_SET_CLOCKEVENT	9
 #define LHCALL_HALT		10
-#define LHCALL_BIND_DMA		12
-#define LHCALL_SEND_DMA		13
 #define LHCALL_SET_PTE		14
 #define LHCALL_SET_PMD		15
 #define LHCALL_LOAD_TLS		16
+#define LHCALL_NOTIFY		17
 
 /*G:031 First, how does our Guest contact the Host to ask for privileged
  * operations?  There are two ways: the direct way is to make a "hypercall",

include/linux/lguest_launcher.h

@@ -10,40 +10,6 @@
 /* How many devices?  Assume each one wants up to two dma arrays per device. */
 #define LGUEST_MAX_DEVICES (LGUEST_MAX_DMA/2)
 
-/*D:200
- * Lguest I/O
- *
- * The lguest I/O mechanism is the only way Guests can talk to devices.  There
- * are two hypercalls involved: SEND_DMA for output and BIND_DMA for input.  In
- * each case, "struct lguest_dma" describes the buffer: this contains 16
- * addr/len pairs, and if there are fewer buffer elements the len array is
- * terminated with a 0.
- *
- * I/O is organized by keys: BIND_DMA attaches buffers to a particular key, and
- * SEND_DMA transfers to buffers bound to particular key.  By convention, keys
- * correspond to a physical address within the device's page.  This means that
- * devices will never accidentally end up with the same keys, and allows the
- * Host use The Futex Trick (as we'll see later in our journey).
- *
- * SEND_DMA simply indicates a key to send to, and the physical address of the
- * "struct lguest_dma" to send.  The Host will write the number of bytes
- * transferred into the "struct lguest_dma"'s used_len member.
- *
- * BIND_DMA indicates a key to bind to, a pointer to an array of "struct
- * lguest_dma"s ready for receiving, the size of that array, and an interrupt
- * to trigger when data is received.  The Host will only allow transfers into
- * buffers with a used_len of zero: it then sets used_len to the number of
- * bytes transferred and triggers the interrupt for the Guest to process the
- * new input. */
-struct lguest_dma
-{
-	/* 0 if free to be used, filled by the Host. */
-	__u32 used_len;
-	__u16 len[LGUEST_MAX_DMA_SECTIONS];
-	unsigned long addr[LGUEST_MAX_DMA_SECTIONS];
-};
-/*:*/
-
 /* Where the Host expects the Guest to SEND_DMA console output to. */
 #define LGUEST_CONSOLE_DMA_KEY 0
 
@@ -95,7 +61,7 @@ struct lguest_device_desc {
 enum lguest_req
 {
 	LHREQ_INITIALIZE, /* + pfnlimit, pgdir, start, pageoffset */
-	LHREQ_GETDMA, /* + addr (returns &lguest_dma, irq in ->used_len) */
+	LHREQ_GETDMA, /* No longer used */
 	LHREQ_IRQ, /* + irq */
 	LHREQ_BREAK, /* + on/off flag (on blocks until someone does off) */
 };