diff options
Diffstat (limited to 'drivers/lguest/io.c')
| -rw-r--r-- | drivers/lguest/io.c | 628 |
1 files changed, 0 insertions, 628 deletions
diff --git a/drivers/lguest/io.c b/drivers/lguest/io.c deleted file mode 100644 index 0e842e9caf68..000000000000 --- a/drivers/lguest/io.c +++ /dev/null @@ -1,628 +0,0 @@ -/*P:300 The I/O mechanism in lguest is simple yet flexible, allowing the Guest - * to talk to the Launcher or directly to another Guest. It uses familiar - * concepts of DMA and interrupts, plus some neat code stolen from - * futexes... :*/ - -/* Copyright (C) 2006 Rusty Russell IBM Corporation - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, write to the Free Software - * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA - */ -#include <linux/types.h> -#include <linux/futex.h> -#include <linux/jhash.h> -#include <linux/mm.h> -#include <linux/highmem.h> -#include <linux/uaccess.h> -#include "lg.h" - -/*L:300 - * I/O - * - * Getting data in and out of the Guest is quite an art. There are numerous - * ways to do it, and they all suck differently. We try to keep things fairly - * close to "real" hardware so our Guest's drivers don't look like an alien - * visitation in the middle of the Linux code, and yet make sure that Guests - * can talk directly to other Guests, not just the Launcher. - * - * To do this, the Guest gives us a key when it binds or sends DMA buffers. - * The key corresponds to a "physical" address inside the Guest (ie. a virtual - * address inside the Launcher process). We don't, however, use this key - * directly. - * - * We want Guests which share memory to be able to DMA to each other: two - * Launchers can mmap memory the same file, then the Guests can communicate. - * Fortunately, the futex code provides us with a way to get a "union - * futex_key" corresponding to the memory lying at a virtual address: if the - * two processes share memory, the "union futex_key" for that memory will match - * even if the memory is mapped at different addresses in each. So we always - * convert the keys to "union futex_key"s to compare them. - * - * Before we dive into this though, we need to look at another set of helper - * routines used throughout the Host kernel code to access Guest memory. - :*/ -static struct list_head dma_hash[61]; - -/* An unfortunate side effect of the Linux double-linked list implementation is - * that there's no good way to statically initialize an array of linked - * lists. */ -void lguest_io_init(void) -{ - unsigned int i; - - for (i = 0; i < ARRAY_SIZE(dma_hash); i++) - INIT_LIST_HEAD(&dma_hash[i]); -} - -/* FIXME: allow multi-page lengths. */ -static int check_dma_list(struct lguest *lg, const struct lguest_dma *dma) -{ - unsigned int i; - - for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) { - if (!dma->len[i]) - return 1; - if (!lguest_address_ok(lg, dma->addr[i], dma->len[i])) - goto kill; - if (dma->len[i] > PAGE_SIZE) - goto kill; - /* We could do over a page, but is it worth it? */ - if ((dma->addr[i] % PAGE_SIZE) + dma->len[i] > PAGE_SIZE) - goto kill; - } - return 1; - -kill: - kill_guest(lg, "bad DMA entry: %u@%#lx", dma->len[i], dma->addr[i]); - return 0; -} - -/*L:330 This is our hash function, using the wonderful Jenkins hash. - * - * The futex key is a union with three parts: an unsigned long word, a pointer, - * and an int "offset". We could use jhash_2words() which takes three u32s. - * (Ok, the hash functions are great: the naming sucks though). - * - * It's nice to be portable to 64-bit platforms, so we use the more generic - * jhash2(), which takes an array of u32, the number of u32s, and an initial - * u32 to roll in. This is uglier, but breaks down to almost the same code on - * 32-bit platforms like this one. - * - * We want a position in the array, so we modulo ARRAY_SIZE(dma_hash) (ie. 61). - */ -static unsigned int hash(const union futex_key *key) -{ - return jhash2((u32*)&key->both.word, - (sizeof(key->both.word)+sizeof(key->both.ptr))/4, - key->both.offset) - % ARRAY_SIZE(dma_hash); -} - -/* This is a convenience routine to compare two keys. It's a much bemoaned C - * weakness that it doesn't allow '==' on structures or unions, so we have to - * open-code it like this. */ -static inline int key_eq(const union futex_key *a, const union futex_key *b) -{ - return (a->both.word == b->both.word - && a->both.ptr == b->both.ptr - && a->both.offset == b->both.offset); -} - -/*L:360 OK, when we need to actually free up a Guest's DMA array we do several - * things, so we have a convenient function to do it. - * - * The caller must hold a read lock on dmainfo owner's current->mm->mmap_sem - * for the drop_futex_key_refs(). */ -static void unlink_dma(struct lguest_dma_info *dmainfo) -{ - /* You locked this too, right? */ - BUG_ON(!mutex_is_locked(&lguest_lock)); - /* This is how we know that the entry is free. */ - dmainfo->interrupt = 0; - /* Remove it from the hash table. */ - list_del(&dmainfo->list); - /* Drop the references we were holding (to the inode or mm). */ - drop_futex_key_refs(&dmainfo->key); -} - -/*L:350 This is the routine which we call when the Guest asks to unregister a - * DMA array attached to a given key. Returns true if the array was found. */ -static int unbind_dma(struct lguest *lg, - const union futex_key *key, - unsigned long dmas) -{ - int i, ret = 0; - - /* We don't bother with the hash table, just look through all this - * Guest's DMA arrays. */ - for (i = 0; i < LGUEST_MAX_DMA; i++) { - /* In theory it could have more than one array on the same key, - * or one array on multiple keys, so we check both */ - if (key_eq(key, &lg->dma[i].key) && dmas == lg->dma[i].dmas) { - unlink_dma(&lg->dma[i]); - ret = 1; - break; - } - } - return ret; -} - -/*L:340 BIND_DMA: this is the hypercall which sets up an array of "struct - * lguest_dma" for receiving I/O. - * - * The Guest wants to bind an array of "struct lguest_dma"s to a particular key - * to receive input. This only happens when the Guest is setting up a new - * device, so it doesn't have to be very fast. - * - * It returns 1 on a successful registration (it can fail if we hit the limit - * of registrations for this Guest). - */ -int bind_dma(struct lguest *lg, - unsigned long ukey, unsigned long dmas, u16 numdmas, u8 interrupt) -{ - unsigned int i; - int ret = 0; - union futex_key key; - /* Futex code needs the mmap_sem. */ - struct rw_semaphore *fshared = ¤t->mm->mmap_sem; - - /* Invalid interrupt? (We could kill the guest here). */ - if (interrupt >= LGUEST_IRQS) - return 0; - - /* We need to grab the Big Lguest Lock, because other Guests may be - * trying to look through this Guest's DMAs to send something while - * we're doing this. */ - mutex_lock(&lguest_lock); - down_read(fshared); - if (get_futex_key(lg->mem_base + ukey, fshared, &key) != 0) { - kill_guest(lg, "bad dma key %#lx", ukey); - goto unlock; - } - - /* We want to keep this key valid once we drop mmap_sem, so we have to - * hold a reference. */ - get_futex_key_refs(&key); - - /* If the Guest specified an interrupt of 0, that means they want to - * unregister this array of "struct lguest_dma"s. */ - if (interrupt == 0) - ret = unbind_dma(lg, &key, dmas); - else { - /* Look through this Guest's dma array for an unused entry. */ - for (i = 0; i < LGUEST_MAX_DMA; i++) { - /* If the interrupt is non-zero, the entry is already - * used. */ - if (lg->dma[i].interrupt) - continue; - - /* OK, a free one! Fill on our details. */ - lg->dma[i].dmas = dmas; - lg->dma[i].num_dmas = numdmas; - lg->dma[i].next_dma = 0; - lg->dma[i].key = key; - lg->dma[i].owner = lg; - lg->dma[i].interrupt = interrupt; - - /* Now we add it to the hash table: the position - * depends on the futex key that we got. */ - list_add(&lg->dma[i].list, &dma_hash[hash(&key)]); - /* Success! */ - ret = 1; - goto unlock; - } - } - /* If we didn't find a slot to put the key in, drop the reference - * again. */ - drop_futex_key_refs(&key); -unlock: - /* Unlock and out. */ - up_read(fshared); - mutex_unlock(&lguest_lock); - return ret; -} - -/*L:385 Note that our routines to access a different Guest's memory are called - * lgread_other() and lgwrite_other(): these names emphasize that they are only - * used when the Guest is *not* the current Guest. - * - * The interface for copying from another process's memory is called - * access_process_vm(), with a final argument of 0 for a read, and 1 for a - * write. - * - * We need lgread_other() to read the destination Guest's "struct lguest_dma" - * array. */ -static int lgread_other(struct lguest *lg, - void *buf, u32 addr, unsigned bytes) -{ - if (!lguest_address_ok(lg, addr, bytes) - || access_process_vm(lg->tsk, (unsigned long)lg->mem_base + addr, - buf, bytes, 0) != bytes) { - memset(buf, 0, bytes); - kill_guest(lg, "bad address in registered DMA struct"); - return 0; - } - return 1; -} - -/* "lgwrite()" to another Guest: used to update the destination "used_len" once - * we've transferred data into the buffer. */ -static int lgwrite_other(struct lguest *lg, u32 addr, - const void *buf, unsigned bytes) -{ - if (!lguest_address_ok(lg, addr, bytes) - || access_process_vm(lg->tsk, (unsigned long)lg->mem_base + addr, - (void *)buf, bytes, 1) != bytes) { - kill_guest(lg, "bad address writing to registered DMA"); - return 0; - } - return 1; -} - -/*L:400 This is the generic engine which copies from a source "struct - * lguest_dma" from this Guest into another Guest's "struct lguest_dma". The - * destination Guest's pages have already been mapped, as contained in the - * pages array. - * - * If you're wondering if there's a nice "copy from one process to another" - * routine, so was I. But Linux isn't really set up to copy between two - * unrelated processes, so we have to write it ourselves. - */ -static u32 copy_data(struct lguest *srclg, - const struct lguest_dma *src, - const struct lguest_dma *dst, - struct page *pages[]) -{ - unsigned int totlen, si, di, srcoff, dstoff; - void *maddr = NULL; - - /* We return the total length transferred. */ - totlen = 0; - - /* We keep indexes into the source and destination "struct lguest_dma", - * and an offset within each region. */ - si = di = 0; - srcoff = dstoff = 0; - - /* We loop until the source or destination is exhausted. */ - while (si < LGUEST_MAX_DMA_SECTIONS && src->len[si] - && di < LGUEST_MAX_DMA_SECTIONS && dst->len[di]) { - /* We can only transfer the rest of the src buffer, or as much - * as will fit into the destination buffer. */ - u32 len = min(src->len[si] - srcoff, dst->len[di] - dstoff); - - /* For systems using "highmem" we need to use kmap() to access - * the page we want. We often use the same page over and over, - * so rather than kmap() it on every loop, we set the maddr - * pointer to NULL when we need to move to the next - * destination page. */ - if (!maddr) - maddr = kmap(pages[di]); - - /* Copy directly from (this Guest's) source address to the - * destination Guest's kmap()ed buffer. Note that maddr points - * to the start of the page: we need to add the offset of the - * destination address and offset within the buffer. */ - - /* FIXME: This is not completely portable. I looked at - * copy_to_user_page(), and some arch's seem to need special - * flushes. x86 is fine. */ - if (copy_from_user(maddr + (dst->addr[di] + dstoff)%PAGE_SIZE, - srclg->mem_base+src->addr[si], len) != 0) { - /* If a copy failed, it's the source's fault. */ - kill_guest(srclg, "bad address in sending DMA"); - totlen = 0; - break; - } - - /* Increment the total and src & dst offsets */ - totlen += len; - srcoff += len; - dstoff += len; - - /* Presumably we reached the end of the src or dest buffers: */ - if (srcoff == src->len[si]) { - /* Move to the next buffer at offset 0 */ - si++; - srcoff = 0; - } - if (dstoff == dst->len[di]) { - /* We need to unmap that destination page and reset - * maddr ready for the next one. */ - kunmap(pages[di]); - maddr = NULL; - di++; - dstoff = 0; - } - } - - /* If we still had a page mapped at the end, unmap now. */ - if (maddr) - kunmap(pages[di]); - - return totlen; -} - -/*L:390 This is how we transfer a "struct lguest_dma" from the source Guest - * (the current Guest which called SEND_DMA) to another Guest. */ -static u32 do_dma(struct lguest *srclg, const struct lguest_dma *src, - struct lguest *dstlg, const struct lguest_dma *dst) -{ - int i; - u32 ret; - struct page *pages[LGUEST_MAX_DMA_SECTIONS]; - - /* We check that both source and destination "struct lguest_dma"s are - * within the bounds of the source and destination Guests */ - if (!check_dma_list(dstlg, dst) || !check_dma_list(srclg, src)) - return 0; - - /* We need to map the pages which correspond to each parts of - * destination buffer. */ - for (i = 0; i < LGUEST_MAX_DMA_SECTIONS; i++) { - if (dst->len[i] == 0) - break; - /* get_user_pages() is a complicated function, especially since - * we only want a single page. But it works, and returns the - * number of pages. Note that we're holding the destination's - * mmap_sem, as get_user_pages() requires. */ - if (get_user_pages(dstlg->tsk, dstlg->mm, - (unsigned long)dstlg->mem_base+dst->addr[i], - 1, 1, 1, pages+i, NULL) - != 1) { - /* This means the destination gave us a bogus buffer */ - kill_guest(dstlg, "Error mapping DMA pages"); - ret = 0; - goto drop_pages; - } - } - - /* Now copy the data until we run out of src or dst. */ - ret = copy_data(srclg, src, dst, pages); - -drop_pages: - while (--i >= 0) - put_page(pages[i]); - return ret; -} - -/*L:380 Transferring data from one Guest to another is not as simple as I'd - * like. We've found the "struct lguest_dma_info" bound to the same address as - * the send, we need to copy into it. - * - * This function returns true if the destination array was empty. */ -static int dma_transfer(struct lguest *srclg, - unsigned long udma, - struct lguest_dma_info *dst) -{ - struct lguest_dma dst_dma, src_dma; - struct lguest *dstlg; - u32 i, dma = 0; - - /* From the "struct lguest_dma_info" we found in the hash, grab the - * Guest. */ - dstlg = dst->owner; - /* Read in the source "struct lguest_dma" handed to SEND_DMA. */ - lgread(srclg, &src_dma, udma, sizeof(src_dma)); - - /* We need the destination's mmap_sem, and we already hold the source's - * mmap_sem for the futex key lookup. Normally this would suggest that - * we could deadlock if the destination Guest was trying to send to - * this source Guest at the same time, which is another reason that all - * I/O is done under the big lguest_lock. */ - down_read(&dstlg->mm->mmap_sem); - - /* Look through the destination DMA array for an available buffer. */ - for (i = 0; i < dst->num_dmas; i++) { - /* We keep a "next_dma" pointer which often helps us avoid - * looking at lots of previously-filled entries. */ - dma = (dst->next_dma + i) % dst->num_dmas; - if (!lgread_other(dstlg, &dst_dma, - dst->dmas + dma * sizeof(struct lguest_dma), - sizeof(dst_dma))) { - goto fail; - } - if (!dst_dma.used_len) - break; - } - - /* If we found a buffer, we do the actual data copy. */ - if (i != dst->num_dmas) { - unsigned long used_lenp; - unsigned int ret; - - ret = do_dma(srclg, &src_dma, dstlg, &dst_dma); - /* Put used length in the source "struct lguest_dma"'s used_len - * field. It's a little tricky to figure out where that is, - * though. */ - lgwrite_u32(srclg, - udma+offsetof(struct lguest_dma, used_len), ret); - /* Tranferring 0 bytes is OK if the source buffer was empty. */ - if (ret == 0 && src_dma.len[0] != 0) - goto fail; - - /* The destination Guest might be running on a different CPU: - * we have to make sure that it will see the "used_len" field - * change to non-zero *after* it sees the data we copied into - * the buffer. Hence a write memory barrier. */ - wmb(); - /* Figuring out where the destination's used_len field for this - * "struct lguest_dma" in the array is also a little ugly. */ - used_lenp = dst->dmas - + dma * sizeof(struct lguest_dma) - + offsetof(struct lguest_dma, used_len); - lgwrite_other(dstlg, used_lenp, &ret, sizeof(ret)); - /* Move the cursor for next time. */ - dst->next_dma++; - } - up_read(&dstlg->mm->mmap_sem); - - /* We trigger the destination interrupt, even if the destination was - * empty and we didn't transfer anything: this gives them a chance to - * wake up and refill. */ - set_bit(dst->interrupt, dstlg->irqs_pending); - /* Wake up the destination process. */ - wake_up_process(dstlg->tsk); - /* If we passed the last "struct lguest_dma", the receive had no - * buffers left. */ - return i == dst->num_dmas; - -fail: - up_read(&dstlg->mm->mmap_sem); - return 0; -} - -/*L:370 This is the counter-side to the BIND_DMA hypercall; the SEND_DMA - * hypercall. We find out who's listening, and send to them. */ -void send_dma(struct lguest *lg, unsigned long ukey, unsigned long udma) -{ - union futex_key key; - int empty = 0; - struct rw_semaphore *fshared = ¤t->mm->mmap_sem; - -again: - mutex_lock(&lguest_lock); - down_read(fshared); - /* Get the futex key for the key the Guest gave us */ - if (get_futex_key(lg->mem_base + ukey, fshared, &key) != 0) { - kill_guest(lg, "bad sending DMA key"); - goto unlock; - } - /* Since the key must be a multiple of 4, the futex key uses the lower - * bit of the "offset" field (which would always be 0) to indicate a - * mapping which is shared with other processes (ie. Guests). */ - if (key.shared.offset & 1) { - struct lguest_dma_info *i; - /* Look through the hash for other Guests. */ - list_for_each_entry(i, &dma_hash[hash(&key)], list) { - /* Don't send to ourselves (would deadlock). */ - if (i->owner->mm == lg->mm) - continue; - if (!key_eq(&key, &i->key)) - continue; - - /* If dma_transfer() tells us the destination has no - * available buffers, we increment "empty". */ - empty += dma_transfer(lg, udma, i); - break; - } - /* If the destination is empty, we release our locks and - * give the destination Guest a brief chance to restock. */ - if (empty == 1) { - /* Give any recipients one chance to restock. */ - up_read(¤t->mm->mmap_sem); - mutex_unlock(&lguest_lock); - /* Next time, we won't try again. */ - empty++; - goto again; - } - } else { - /* Private mapping: Guest is sending to its Launcher. We set - * the "dma_is_pending" flag so that the main loop will exit - * and the Launcher's read() from /dev/lguest will return. */ - lg->dma_is_pending = 1; - lg->pending_dma = udma; - lg->pending_key = ukey; - } -unlock: - up_read(fshared); - mutex_unlock(&lguest_lock); -} -/*:*/ - -void release_all_dma(struct lguest *lg) -{ - unsigned int i; - - BUG_ON(!mutex_is_locked(&lguest_lock)); - - down_read(&lg->mm->mmap_sem); - for (i = 0; i < LGUEST_MAX_DMA; i++) { - if (lg->dma[i].interrupt) - unlink_dma(&lg->dma[i]); - } - up_read(&lg->mm->mmap_sem); -} - -/*M:007 We only return a single DMA buffer to the Launcher, but it would be - * more efficient to return a pointer to the entire array of DMA buffers, which - * it can cache and choose one whenever it wants. - * - * Currently the Launcher uses a write to /dev/lguest, and the return value is - * the address of the DMA structure with the interrupt number placed in - * dma->used_len. If we wanted to return the entire array, we need to return - * the address, array size and interrupt number: this seems to require an - * ioctl(). :*/ - -/*L:320 This routine looks for a DMA buffer registered by the Guest on the - * given key (using the BIND_DMA hypercall). */ -unsigned long get_dma_buffer(struct lguest *lg, - unsigned long ukey, unsigned long *interrupt) -{ - unsigned long ret = 0; - union futex_key key; - struct lguest_dma_info *i; - struct rw_semaphore *fshared = ¤t->mm->mmap_sem; - - /* Take the Big Lguest Lock to stop other Guests sending this Guest DMA - * at the same time. */ - mutex_lock(&lguest_lock); - /* To match between Guests sharing the same underlying memory we steal - * code from the futex infrastructure. This requires that we hold the - * "mmap_sem" for our process (the Launcher), and pass it to the futex - * code. */ - down_read(fshared); - - /* This can fail if it's not a valid address, or if the address is not - * divisible by 4 (the futex code needs that, we don't really). */ - if (get_futex_key(lg->mem_base + ukey, fshared, &key) != 0) { - kill_guest(lg, "bad registered DMA buffer"); - goto unlock; - } - /* Search the hash table for matching entries (the Launcher can only - * send to its own Guest for the moment, so the entry must be for this - * Guest) */ - list_for_each_entry(i, &dma_hash[hash(&key)], list) { - if (key_eq(&key, &i->key) && i->owner == lg) { - unsigned int j; - /* Look through the registered DMA array for an - * available buffer. */ - for (j = 0; j < i->num_dmas; j++) { - struct lguest_dma dma; - - ret = i->dmas + j * sizeof(struct lguest_dma); - lgread(lg, &dma, ret, sizeof(dma)); - if (dma.used_len == 0) - break; - } - /* Store the interrupt the Guest wants when the buffer - * is used. */ - *interrupt = i->interrupt; - break; - } - } -unlock: - up_read(fshared); - mutex_unlock(&lguest_lock); - return ret; -} -/*:*/ - -/*L:410 This really has completed the Launcher. Not only have we now finished - * the longest chapter in our journey, but this also means we are over halfway - * through! - * - * Enough prevaricating around the bush: it is time for us to dive into the - * core of the Host, in "make Host". - */ |