diff options
Diffstat (limited to 'drivers/lguest')
| -rw-r--r-- | drivers/lguest/core.c | 18 | ||||
| -rw-r--r-- | drivers/lguest/hypercalls.c | 11 | ||||
| -rw-r--r-- | drivers/lguest/interrupts_and_traps.c | 7 | ||||
| -rw-r--r-- | drivers/lguest/lguest_device.c | 11 | ||||
| -rw-r--r-- | drivers/lguest/lguest_user.c | 30 | ||||
| -rw-r--r-- | drivers/lguest/page_tables.c | 32 | ||||
| -rw-r--r-- | drivers/lguest/x86/core.c | 33 | ||||
| -rw-r--r-- | drivers/lguest/x86/switcher_32.S | 8 |
8 files changed, 91 insertions, 59 deletions
diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c index c632c08cbbdc..5eea4356d703 100644 --- a/drivers/lguest/core.c +++ b/drivers/lguest/core.c @@ -1,8 +1,6 @@ /*P:400 This contains run_guest() which actually calls into the Host<->Guest * Switcher and analyzes the return, such as determining if the Guest wants the - * Host to do something. This file also contains useful helper routines, and a - * couple of non-obvious setup and teardown pieces which were implemented after - * days of debugging pain. :*/ + * Host to do something. This file also contains useful helper routines. :*/ #include <linux/module.h> #include <linux/stringify.h> #include <linux/stddef.h> @@ -49,8 +47,8 @@ static __init int map_switcher(void) * easy. */ - /* We allocate an array of "struct page"s. map_vm_area() wants the - * pages in this form, rather than just an array of pointers. */ + /* We allocate an array of struct page pointers. map_vm_area() wants + * this, rather than just an array of pages. */ switcher_page = kmalloc(sizeof(switcher_page[0])*TOTAL_SWITCHER_PAGES, GFP_KERNEL); if (!switcher_page) { @@ -172,7 +170,7 @@ void __lgread(struct lg_cpu *cpu, void *b, unsigned long addr, unsigned bytes) } } -/* This is the write (copy into guest) version. */ +/* This is the write (copy into Guest) version. */ void __lgwrite(struct lg_cpu *cpu, unsigned long addr, const void *b, unsigned bytes) { @@ -209,9 +207,9 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) if (cpu->break_out) return -EAGAIN; - /* Check if there are any interrupts which can be delivered - * now: if so, this sets up the hander to be executed when we - * next run the Guest. */ + /* Check if there are any interrupts which can be delivered now: + * if so, this sets up the hander to be executed when we next + * run the Guest. */ maybe_do_interrupt(cpu); /* All long-lived kernel loops need to check with this horrible @@ -246,8 +244,10 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user) lguest_arch_handle_trap(cpu); } + /* Special case: Guest is 'dead' but wants a reboot. */ if (cpu->lg->dead == ERR_PTR(-ERESTART)) return -ERESTART; + /* The Guest is dead => "No such file or directory" */ return -ENOENT; } diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c index 0f2cb4fd7c69..54d66f05fefa 100644 --- a/drivers/lguest/hypercalls.c +++ b/drivers/lguest/hypercalls.c @@ -29,7 +29,7 @@ #include "lg.h" /*H:120 This is the core hypercall routine: where the Guest gets what it wants. - * Or gets killed. Or, in the case of LHCALL_CRASH, both. */ + * Or gets killed. Or, in the case of LHCALL_SHUTDOWN, both. */ static void do_hcall(struct lg_cpu *cpu, struct hcall_args *args) { switch (args->arg0) { @@ -190,6 +190,13 @@ static void initialize(struct lg_cpu *cpu) * pagetable. */ guest_pagetable_clear_all(cpu); } +/*:*/ + +/*M:013 If a Guest reads from a page (so creates a mapping) that it has never + * written to, and then the Launcher writes to it (ie. the output of a virtual + * device), the Guest will still see the old page. In practice, this never + * happens: why would the Guest read a page which it has never written to? But + * a similar scenario might one day bite us, so it's worth mentioning. :*/ /*H:100 * Hypercalls @@ -227,7 +234,7 @@ void do_hypercalls(struct lg_cpu *cpu) * However, if we are signalled or the Guest sends I/O to the * Launcher, the run_guest() loop will exit without running the * Guest. When it comes back it would try to re-run the - * hypercall. */ + * hypercall. Finding that bug sucked. */ cpu->hcall = NULL; } } diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c index 32e97c1858e5..0414ddf87587 100644 --- a/drivers/lguest/interrupts_and_traps.c +++ b/drivers/lguest/interrupts_and_traps.c @@ -144,7 +144,6 @@ void maybe_do_interrupt(struct lg_cpu *cpu) if (copy_from_user(&blk, cpu->lg->lguest_data->blocked_interrupts, sizeof(blk))) return; - bitmap_andnot(blk, cpu->irqs_pending, blk, LGUEST_IRQS); /* Find the first interrupt. */ @@ -237,9 +236,9 @@ void free_interrupts(void) clear_bit(syscall_vector, used_vectors); } -/*H:220 Now we've got the routines to deliver interrupts, delivering traps - * like page fault is easy. The only trick is that Intel decided that some - * traps should have error codes: */ +/*H:220 Now we've got the routines to deliver interrupts, delivering traps like + * page fault is easy. The only trick is that Intel decided that some traps + * should have error codes: */ static int has_err(unsigned int trap) { return (trap == 8 || (trap >= 10 && trap <= 14) || trap == 17); diff --git a/drivers/lguest/lguest_device.c b/drivers/lguest/lguest_device.c index 1b2ec0bf5eb1..2bc9bf7e88e5 100644 --- a/drivers/lguest/lguest_device.c +++ b/drivers/lguest/lguest_device.c @@ -1,10 +1,10 @@ /*P:050 Lguest guests use a very simple method to describe devices. It's a - * series of device descriptors contained just above the top of normal + * series of device descriptors contained just above the top of normal Guest * memory. * * We use the standard "virtio" device infrastructure, which provides us with a * console, a network and a block driver. Each one expects some configuration - * information and a "virtqueue" mechanism to send and receive data. :*/ + * information and a "virtqueue" or two to send and receive data. :*/ #include <linux/init.h> #include <linux/bootmem.h> #include <linux/lguest_launcher.h> @@ -53,7 +53,7 @@ struct lguest_device { * Device configurations * * The configuration information for a device consists of one or more - * virtqueues, a feature bitmaks, and some configuration bytes. The + * virtqueues, a feature bitmap, and some configuration bytes. The * configuration bytes don't really matter to us: the Launcher sets them up, and * the driver will look at them during setup. * @@ -179,7 +179,7 @@ struct lguest_vq_info }; /* When the virtio_ring code wants to prod the Host, it calls us here and we - * make a hypercall. We hand the page number of the virtqueue so the Host + * make a hypercall. We hand the physical address of the virtqueue so the Host * knows which virtqueue we're talking about. */ static void lg_notify(struct virtqueue *vq) { @@ -199,7 +199,8 @@ static void lg_notify(struct virtqueue *vq) * allocate its own pages and tell the Host where they are, but for lguest it's * simpler for the Host to simply tell us where the pages are. * - * So we provide devices with a "find virtqueue and set it up" function. */ + * So we provide drivers with a "find the Nth virtqueue and set it up" + * function. */ static struct virtqueue *lg_find_vq(struct virtio_device *vdev, unsigned index, void (*callback)(struct virtqueue *vq)) diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c index 2221485b0773..564e425d71dd 100644 --- a/drivers/lguest/lguest_user.c +++ b/drivers/lguest/lguest_user.c @@ -73,7 +73,7 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) if (current != cpu->tsk) return -EPERM; - /* If the guest is already dead, we indicate why */ + /* If the Guest is already dead, we indicate why */ if (lg->dead) { size_t len; @@ -88,7 +88,7 @@ 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 notified, + /* If we returned from read() last time because the Guest sent I/O, * clear the flag. */ if (cpu->pending_notify) cpu->pending_notify = 0; @@ -97,14 +97,20 @@ static ssize_t read(struct file *file, char __user *user, size_t size,loff_t*o) return run_guest(cpu, (unsigned long __user *)user); } +/*L:025 This actually initializes a CPU. For the moment, a Guest is only + * uniprocessor, so "id" is always 0. */ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip) { + /* We have a limited number the number of CPUs in the lguest struct. */ if (id >= NR_CPUS) return -EINVAL; + /* Set up this CPU's id, and pointer back to the lguest struct. */ cpu->id = id; cpu->lg = container_of((cpu - id), struct lguest, cpus[0]); cpu->lg->nr_cpus++; + + /* Each CPU has a timer it can set. */ init_clockdev(cpu); /* We need a complete page for the Guest registers: they are accessible @@ -120,11 +126,11 @@ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip) * address. */ lguest_arch_setup_regs(cpu, start_ip); - /* Initialize the queue for the waker to wait on */ + /* Initialize the queue for the Waker to wait on */ init_waitqueue_head(&cpu->break_wq); /* We keep a pointer to the Launcher task (ie. current task) for when - * other Guests want to wake this one (inter-Guest I/O). */ + * other Guests want to wake this one (eg. console input). */ cpu->tsk = current; /* We need to keep a pointer to the Launcher's memory map, because if @@ -136,6 +142,7 @@ static int lg_cpu_start(struct lg_cpu *cpu, unsigned id, unsigned long start_ip) * when the same Guest runs on the same CPU twice. */ cpu->last_pages = NULL; + /* No error == success. */ return 0; } @@ -185,14 +192,13 @@ static int initialize(struct file *file, const unsigned long __user *input) lg->mem_base = (void __user *)(long)args[0]; lg->pfn_limit = args[1]; - /* This is the first cpu */ + /* This is the first cpu (cpu 0) and it will start booting at args[3] */ err = lg_cpu_start(&lg->cpus[0], 0, args[3]); if (err) goto release_guest; /* Initialize the Guest's shadow page tables, using the toplevel - * address the Launcher gave us. This allocates memory, so can - * fail. */ + * address the Launcher gave us. This allocates memory, so can fail. */ err = init_guest_pagetable(lg, args[2]); if (err) goto free_regs; @@ -218,11 +224,16 @@ unlock: /*L:010 The first operation the Launcher does must be a write. All writes * start with an unsigned long 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 send interrupts. */ + * writes of other values to send interrupts. + * + * Note that we overload the "offset" in the /dev/lguest file to indicate what + * CPU number we're dealing with. Currently this is always 0, since we only + * support uniprocessor Guests, but you can see the beginnings of SMP support + * here. */ static ssize_t write(struct file *file, const char __user *in, size_t size, loff_t *off) { - /* Once the guest is initialized, we hold the "struct lguest" in the + /* Once the Guest is initialized, we hold the "struct lguest" in the * file private data. */ struct lguest *lg = file->private_data; const unsigned long __user *input = (const unsigned long __user *)in; @@ -230,6 +241,7 @@ static ssize_t write(struct file *file, const char __user *in, struct lg_cpu *uninitialized_var(cpu); unsigned int cpu_id = *off; + /* The first value tells us what this request is. */ if (get_user(req, input) != 0) return -EFAULT; input++; diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c index a7f64a9d67e0..d93500f24fbb 100644 --- a/drivers/lguest/page_tables.c +++ b/drivers/lguest/page_tables.c @@ -2,8 +2,8 @@ * previous encounters. It's functional, and as neat as it can be in the * circumstances, but be wary, for these things are subtle and break easily. * The Guest provides a virtual to physical mapping, but we can neither trust - * it nor use it: we verify and convert it here to point the hardware to the - * actual Guest pages when running the Guest. :*/ + * it nor use it: we verify and convert it here then point the CPU to the + * converted Guest pages when running the Guest. :*/ /* Copyright (C) Rusty Russell IBM Corporation 2006. * GPL v2 and any later version */ @@ -106,6 +106,11 @@ static unsigned long gpte_addr(pgd_t gpgd, unsigned long vaddr) BUG_ON(!(pgd_flags(gpgd) & _PAGE_PRESENT)); return gpage + ((vaddr>>PAGE_SHIFT) % PTRS_PER_PTE) * sizeof(pte_t); } +/*:*/ + +/*M:014 get_pfn is slow; it takes the mmap sem and calls get_user_pages. We + * could probably try to grab batches of pages here as an optimization + * (ie. pre-faulting). :*/ /*H:350 This routine takes a page number given by the Guest and converts it to * an actual, physical page number. It can fail for several reasons: the @@ -113,8 +118,8 @@ static unsigned long gpte_addr(pgd_t gpgd, unsigned long vaddr) * and the page is read-only, or the write flag was set and the page was * shared so had to be copied, but we ran out of memory. * - * This holds a reference to the page, so release_pte() is careful to - * put that back. */ + * This holds a reference to the page, so release_pte() is careful to put that + * back. */ static unsigned long get_pfn(unsigned long virtpfn, int write) { struct page *page; @@ -532,13 +537,13 @@ static void do_set_pte(struct lg_cpu *cpu, int idx, * all processes. So when the page table above that address changes, we update * all the page tables, not just the current one. This is rare. * - * The benefit is that when we have to track a new page table, we can copy keep - * all the kernel mappings. This speeds up context switch immensely. */ + * The benefit is that when we have to track a new page table, we can keep all + * the kernel mappings. This speeds up context switch immensely. */ void guest_set_pte(struct lg_cpu *cpu, unsigned long gpgdir, unsigned long vaddr, pte_t gpte) { - /* Kernel mappings must be changed on all top levels. Slow, but - * doesn't happen often. */ + /* Kernel mappings must be changed on all top levels. Slow, but doesn't + * happen often. */ if (vaddr >= cpu->lg->kernel_address) { unsigned int i; for (i = 0; i < ARRAY_SIZE(cpu->lg->pgdirs); i++) @@ -704,12 +709,11 @@ static __init void populate_switcher_pte_page(unsigned int cpu, /* We've made it through the page table code. Perhaps our tired brains are * still processing the details, or perhaps we're simply glad it's over. * - * If nothing else, note that all this complexity in juggling shadow page - * tables in sync with the Guest's page tables is for one reason: for most - * Guests this page table dance determines how bad performance will be. This - * is why Xen uses exotic direct Guest pagetable manipulation, and why both - * Intel and AMD have implemented shadow page table support directly into - * hardware. + * If nothing else, note that all this complexity in juggling shadow page tables + * in sync with the Guest's page tables is for one reason: for most Guests this + * page table dance determines how bad performance will be. This is why Xen + * uses exotic direct Guest pagetable manipulation, and why both Intel and AMD + * have implemented shadow page table support directly into hardware. * * There is just one file remaining in the Host. */ diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c index 635187812d52..5126d5d9ea0e 100644 --- a/drivers/lguest/x86/core.c +++ b/drivers/lguest/x86/core.c @@ -17,6 +17,13 @@ * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ +/*P:450 This file contains the x86-specific lguest code. It used to be all + * mixed in with drivers/lguest/core.c but several foolhardy code slashers + * wrestled most of the dependencies out to here in preparation for porting + * lguest to other architectures (see what I mean by foolhardy?). + * + * This also contains a couple of non-obvious setup and teardown pieces which + * were implemented after days of debugging pain. :*/ #include <linux/kernel.h> #include <linux/start_kernel.h> #include <linux/string.h> @@ -157,6 +164,8 @@ static void run_guest_once(struct lg_cpu *cpu, struct lguest_pages *pages) * also simplify copy_in_guest_info(). Note that we'd still need to restore * things when we exit to Launcher userspace, but that's fairly easy. * + * We could also try using this hooks for PGE, but that might be too expensive. + * * The hooks were designed for KVM, but we can also put them to good use. :*/ /*H:040 This is the i386-specific code to setup and run the Guest. Interrupts @@ -182,7 +191,7 @@ void lguest_arch_run_guest(struct lg_cpu *cpu) * was doing. */ run_guest_once(cpu, lguest_pages(raw_smp_processor_id())); - /* Note that the "regs" pointer contains two extra entries which are + /* Note that the "regs" structure contains two extra entries which are * not really registers: a trap number which says what interrupt or * trap made the switcher code come back, and an error code which some * traps set. */ @@ -293,11 +302,10 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu) break; case 14: /* We've intercepted a Page Fault. */ /* The Guest accessed a virtual address that wasn't mapped. - * This happens a lot: we don't actually set up most of the - * page tables for the Guest at all when we start: as it runs - * it asks for more and more, and we set them up as - * required. In this case, we don't even tell the Guest that - * the fault happened. + * This happens a lot: we don't actually set up most of the page + * tables for the Guest at all when we start: as it runs it asks + * for more and more, and we set them up as required. In this + * case, we don't even tell the Guest that the fault happened. * * The errcode tells whether this was a read or a write, and * whether kernel or userspace code. */ @@ -342,7 +350,7 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu) if (!deliver_trap(cpu, cpu->regs->trapnum)) /* If the Guest doesn't have a handler (either it hasn't * registered any yet, or it's one of the faults we don't let - * it handle), it dies with a cryptic error message. */ + * it handle), it dies with this cryptic error message. */ kill_guest(cpu, "unhandled trap %li at %#lx (%#lx)", cpu->regs->trapnum, cpu->regs->eip, cpu->regs->trapnum == 14 ? cpu->arch.last_pagefault @@ -375,8 +383,8 @@ void __init lguest_arch_host_init(void) * The only exception is the interrupt handlers in switcher.S: their * addresses are placed in a table (default_idt_entries), so we need to * update the table with the new addresses. switcher_offset() is a - * convenience function which returns the distance between the builtin - * switcher code and the high-mapped copy we just made. */ + * convenience function which returns the distance between the + * compiled-in switcher code and the high-mapped copy we just made. */ for (i = 0; i < IDT_ENTRIES; i++) default_idt_entries[i] += switcher_offset(); @@ -416,7 +424,7 @@ void __init lguest_arch_host_init(void) state->guest_gdt_desc.address = (long)&state->guest_gdt; /* We know where we want the stack to be when the Guest enters - * the switcher: in pages->regs. The stack grows upwards, so + * the Switcher: in pages->regs. The stack grows upwards, so * we start it at the end of that structure. */ state->guest_tss.sp0 = (long)(&pages->regs + 1); /* And this is the GDT entry to use for the stack: we keep a @@ -513,8 +521,8 @@ int lguest_arch_init_hypercalls(struct lg_cpu *cpu) { u32 tsc_speed; - /* The pointer to the Guest's "struct lguest_data" is the only - * argument. We check that address now. */ + /* The pointer to the Guest's "struct lguest_data" is the only argument. + * We check that address now. */ if (!lguest_address_ok(cpu->lg, cpu->hcall->arg1, sizeof(*cpu->lg->lguest_data))) return -EFAULT; @@ -546,6 +554,7 @@ int lguest_arch_init_hypercalls(struct lg_cpu *cpu) return 0; } +/*:*/ /*L:030 lguest_arch_setup_regs() * diff --git a/drivers/lguest/x86/switcher_32.S b/drivers/lguest/x86/switcher_32.S index 0af8baaa0d4a..3fc15318a80f 100644 --- a/drivers/lguest/x86/switcher_32.S +++ b/drivers/lguest/x86/switcher_32.S @@ -1,6 +1,6 @@ -/*P:900 This is the Switcher: code which sits at 0xFFC00000 to do the low-level - * Guest<->Host switch. It is as simple as it can be made, but it's naturally - * very specific to x86. +/*P:900 This is the Switcher: code which sits at 0xFFC00000 astride both the + * Host and Guest to do the low-level Guest<->Host switch. It is as simple as + * it can be made, but it's naturally very specific to x86. * * You have now completed Preparation. If this has whet your appetite; if you * are feeling invigorated and refreshed then the next, more challenging stage @@ -189,7 +189,7 @@ ENTRY(switch_to_guest) // Interrupts are turned back on: we are Guest. iret -// We treat two paths to switch back to the Host +// We tread two paths to switch back to the Host // Yet both must save Guest state and restore Host // So we put the routine in a macro. #define SWITCH_TO_HOST \ |