lguest: the guest code

lguest is a simple hypervisor for Linux on Linux.  Unlike kvm it doesn't need
VT/SVM hardware.  Unlike Xen it's simply "modprobe and go".  Unlike both, it's
5000 lines and self-contained.

Performance is ok, but not great (-30% on kernel compile).  But given its
hackability, I expect this to improve, along with the paravirt_ops code which
it supplies a complete example for.  There's also a 64-bit version being
worked on and other craziness.

But most of all, lguest is awesome fun!  Too much of the kernel is a big ball
of hair.  lguest is simple enough to dive into and hack, plus has some warts
which scream "fork me!".

This patch:

This is the code and headers required to make an i386 kernel an lguest guest.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Andi Kleen <ak@suse.de>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 544 insertions, 0 deletions

diff --git a/drivers/lguest/lguest.c b/drivers/lguest/lguest.c
new file mode 100644
index 000000000000..b3a72bd8d6f5
--- /dev/null
+++ b/drivers/lguest/lguest.c
@@ -0,0 +1,544 @@
+/*
+ * Lguest specific paravirt-ops implementation
+ *
+ * Copyright (C) 2006, Rusty Russell <rusty@rustcorp.com.au> 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, GOOD TITLE or
+ * NON INFRINGEMENT.  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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+#include <linux/kernel.h>
+#include <linux/start_kernel.h>
+#include <linux/string.h>
+#include <linux/console.h>
+#include <linux/screen_info.h>
+#include <linux/irq.h>
+#include <linux/interrupt.h>
+#include <linux/lguest.h>
+#include <linux/lguest_launcher.h>
+#include <linux/lguest_bus.h>
+#include <asm/paravirt.h>
+#include <asm/param.h>
+#include <asm/page.h>
+#include <asm/pgtable.h>
+#include <asm/desc.h>
+#include <asm/setup.h>
+#include <asm/e820.h>
+#include <asm/mce.h>
+#include <asm/io.h>
+
+/* Declarations for definitions in lguest_guest.S */
+extern char lguest_noirq_start[], lguest_noirq_end[];
+extern const char lgstart_cli[], lgend_cli[];
+extern const char lgstart_sti[], lgend_sti[];
+extern const char lgstart_popf[], lgend_popf[];
+extern const char lgstart_pushf[], lgend_pushf[];
+extern const char lgstart_iret[], lgend_iret[];
+extern void lguest_iret(void);
+
+struct lguest_data lguest_data = {
+        .hcall_status = { [0 ... LHCALL_RING_SIZE-1] = 0xFF },
+        .noirq_start = (u32)lguest_noirq_start,
+        .noirq_end = (u32)lguest_noirq_end,
+        .blocked_interrupts = { 1 }, /* Block timer interrupts */
+};
+struct lguest_device_desc *lguest_devices;
+static __initdata const struct lguest_boot_info *boot = __va(0);
+
+static enum paravirt_lazy_mode lazy_mode;
+static void lguest_lazy_mode(enum paravirt_lazy_mode mode)
+{
+        if (mode == PARAVIRT_LAZY_FLUSH) {
+                if (unlikely(lazy_mode != PARAVIRT_LAZY_NONE))
+                        hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0);
+        } else {
+                lazy_mode = mode;
+                if (mode == PARAVIRT_LAZY_NONE)
+                        hcall(LHCALL_FLUSH_ASYNC, 0, 0, 0);
+        }
+}
+
+static void lazy_hcall(unsigned long call,
+                       unsigned long arg1,
+                       unsigned long arg2,
+                       unsigned long arg3)
+{
+        if (lazy_mode == PARAVIRT_LAZY_NONE)
+                hcall(call, arg1, arg2, arg3);
+        else
+                async_hcall(call, arg1, arg2, arg3);
+}
+
+void async_hcall(unsigned long call,
+                 unsigned long arg1, unsigned long arg2, unsigned long arg3)
+{
+        /* Note: This code assumes we're uniprocessor. */
+        static unsigned int next_call;
+        unsigned long flags;
+
+        local_irq_save(flags);
+        if (lguest_data.hcall_status[next_call] != 0xFF) {
+                /* Table full, so do normal hcall which will flush table. */
+                hcall(call, arg1, arg2, arg3);
+        } else {
+                lguest_data.hcalls[next_call].eax = call;
+                lguest_data.hcalls[next_call].edx = arg1;
+                lguest_data.hcalls[next_call].ebx = arg2;
+                lguest_data.hcalls[next_call].ecx = arg3;
+                /* Make sure host sees arguments before "valid" flag. */
+                wmb();
+                lguest_data.hcall_status[next_call] = 0;
+                if (++next_call == LHCALL_RING_SIZE)
+                        next_call = 0;
+        }
+        local_irq_restore(flags);
+}
+
+void lguest_send_dma(unsigned long key, struct lguest_dma *dma)
+{
+        dma->used_len = 0;
+        hcall(LHCALL_SEND_DMA, key, __pa(dma), 0);
+}
+
+int lguest_bind_dma(unsigned long key, struct lguest_dma *dmas,
+                    unsigned int num, u8 irq)
+{
+        if (!hcall(LHCALL_BIND_DMA, key, __pa(dmas), (num << 8) | irq))
+                return -ENOMEM;
+        return 0;
+}
+
+void lguest_unbind_dma(unsigned long key, struct lguest_dma *dmas)
+{
+        hcall(LHCALL_BIND_DMA, key, __pa(dmas), 0);
+}
+
+/* For guests, device memory can be used as normal memory, so we cast away the
+ * __iomem to quieten sparse. */
+void *lguest_map(unsigned long phys_addr, unsigned long pages)
+{
+        return (__force void *)ioremap(phys_addr, PAGE_SIZE*pages);
+}
+
+void lguest_unmap(void *addr)
+{
+        iounmap((__force void __iomem *)addr);
+}
+
+static unsigned long save_fl(void)
+{
+        return lguest_data.irq_enabled;
+}
+
+static void restore_fl(unsigned long flags)
+{
+        /* FIXME: Check if interrupt pending... */
+        lguest_data.irq_enabled = flags;
+}
+
+static void irq_disable(void)
+{
+        lguest_data.irq_enabled = 0;
+}
+
+static void irq_enable(void)
+{
+        /* FIXME: Check if interrupt pending... */
+        lguest_data.irq_enabled = X86_EFLAGS_IF;
+}
+
+static void lguest_write_idt_entry(struct desc_struct *dt,
+                                   int entrynum, u32 low, u32 high)
+{
+        write_dt_entry(dt, entrynum, low, high);
+        hcall(LHCALL_LOAD_IDT_ENTRY, entrynum, low, high);
+}
+
+static void lguest_load_idt(const struct Xgt_desc_struct *desc)
+{
+        unsigned int i;
+        struct desc_struct *idt = (void *)desc->address;
+
+        for (i = 0; i < (desc->size+1)/8; i++)
+                hcall(LHCALL_LOAD_IDT_ENTRY, i, idt[i].a, idt[i].b);
+}
+
+static void lguest_load_gdt(const struct Xgt_desc_struct *desc)
+{
+        BUG_ON((desc->size+1)/8 != GDT_ENTRIES);
+        hcall(LHCALL_LOAD_GDT, __pa(desc->address), GDT_ENTRIES, 0);
+}
+
+static void lguest_write_gdt_entry(struct desc_struct *dt,
+                                   int entrynum, u32 low, u32 high)
+{
+        write_dt_entry(dt, entrynum, low, high);
+        hcall(LHCALL_LOAD_GDT, __pa(dt), GDT_ENTRIES, 0);
+}
+
+static void lguest_load_tls(struct thread_struct *t, unsigned int cpu)
+{
+        lazy_hcall(LHCALL_LOAD_TLS, __pa(&t->tls_array), cpu, 0);
+}
+
+static void lguest_set_ldt(const void *addr, unsigned entries)
+{
+}
+
+static void lguest_load_tr_desc(void)
+{
+}
+
+static void lguest_cpuid(unsigned int *eax, unsigned int *ebx,
+                         unsigned int *ecx, unsigned int *edx)
+{
+        int function = *eax;
+
+        native_cpuid(eax, ebx, ecx, edx);
+        switch (function) {
+        case 1: /* Basic feature request. */
+                /* We only allow kernel to see SSE3, CMPXCHG16B and SSSE3 */
+                *ecx &= 0x00002201;
+                /* Similarly: SSE, SSE2, FXSR, MMX, CMOV, CMPXCHG8B, FPU. */
+                *edx &= 0x07808101;
+                /* Host wants to know when we flush kernel pages: set PGE. */
+                *edx |= 0x00002000;
+                break;
+        case 0x80000000:
+                /* Futureproof this a little: if they ask how much extended
+                 * processor information, limit it to known fields. */
+                if (*eax > 0x80000008)
+                        *eax = 0x80000008;
+                break;
+        }
+}
+
+static unsigned long current_cr0, current_cr3;
+static void lguest_write_cr0(unsigned long val)
+{
+        lazy_hcall(LHCALL_TS, val & 8, 0, 0);
+        current_cr0 = val;
+}
+
+static unsigned long lguest_read_cr0(void)
+{
+        return current_cr0;
+}
+
+static void lguest_clts(void)
+{
+        lazy_hcall(LHCALL_TS, 0, 0, 0);
+        current_cr0 &= ~8U;
+}
+
+static unsigned long lguest_read_cr2(void)
+{
+        return lguest_data.cr2;
+}
+
+static void lguest_write_cr3(unsigned long cr3)
+{
+        lazy_hcall(LHCALL_NEW_PGTABLE, cr3, 0, 0);
+        current_cr3 = cr3;
+}
+
+static unsigned long lguest_read_cr3(void)
+{
+        return current_cr3;
+}
+
+/* Used to enable/disable PGE, but we don't care. */
+static unsigned long lguest_read_cr4(void)
+{
+        return 0;
+}
+
+static void lguest_write_cr4(unsigned long val)
+{
+}
+
+static void lguest_set_pte_at(struct mm_struct *mm, unsigned long addr,
+                              pte_t *ptep, pte_t pteval)
+{
+        *ptep = pteval;
+        lazy_hcall(LHCALL_SET_PTE, __pa(mm->pgd), addr, pteval.pte_low);
+}
+
+/* We only support two-level pagetables at the moment. */
+static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval)
+{
+        *pmdp = pmdval;
+        lazy_hcall(LHCALL_SET_PMD, __pa(pmdp)&PAGE_MASK,
+                   (__pa(pmdp)&(PAGE_SIZE-1))/4, 0);
+}
+
+/* FIXME: Eliminate all callers of this. */
+static void lguest_set_pte(pte_t *ptep, pte_t pteval)
+{
+        *ptep = pteval;
+        /* Don't bother with hypercall before initial setup. */
+        if (current_cr3)
+                lazy_hcall(LHCALL_FLUSH_TLB, 1, 0, 0);
+}
+
+static void lguest_flush_tlb_single(unsigned long addr)
+{
+        /* Simply set it to zero, and it will fault back in. */
+        lazy_hcall(LHCALL_SET_PTE, current_cr3, addr, 0);
+}
+
+static void lguest_flush_tlb_user(void)
+{
+        lazy_hcall(LHCALL_FLUSH_TLB, 0, 0, 0);
+}
+
+static void lguest_flush_tlb_kernel(void)
+{
+        lazy_hcall(LHCALL_FLUSH_TLB, 1, 0, 0);
+}
+
+static void disable_lguest_irq(unsigned int irq)
+{
+        set_bit(irq, lguest_data.blocked_interrupts);
+}
+
+static void enable_lguest_irq(unsigned int irq)
+{
+        clear_bit(irq, lguest_data.blocked_interrupts);
+        /* FIXME: If it's pending? */
+}
+
+static struct irq_chip lguest_irq_controller = {
+        .name           = "lguest",
+        .mask           = disable_lguest_irq,
+        .mask_ack       = disable_lguest_irq,
+        .unmask         = enable_lguest_irq,
+};
+
+static void __init lguest_init_IRQ(void)
+{
+        unsigned int i;
+
+        for (i = 0; i < LGUEST_IRQS; i++) {
+                int vector = FIRST_EXTERNAL_VECTOR + i;
+                if (vector != SYSCALL_VECTOR) {
+                        set_intr_gate(vector, interrupt[i]);
+                        set_irq_chip_and_handler(i, &lguest_irq_controller,
+                                                 handle_level_irq);
+                }
+        }
+        irq_ctx_init(smp_processor_id());
+}
+
+static unsigned long lguest_get_wallclock(void)
+{
+        return hcall(LHCALL_GET_WALLCLOCK, 0, 0, 0);
+}
+
+static void lguest_time_irq(unsigned int irq, struct irq_desc *desc)
+{
+        do_timer(hcall(LHCALL_TIMER_READ, 0, 0, 0));
+        update_process_times(user_mode_vm(get_irq_regs()));
+}
+
+static u64 sched_clock_base;
+static void lguest_time_init(void)
+{
+        set_irq_handler(0, lguest_time_irq);
+        hcall(LHCALL_TIMER_READ, 0, 0, 0);
+        sched_clock_base = jiffies_64;
+        enable_lguest_irq(0);
+}
+
+static unsigned long long lguest_sched_clock(void)
+{
+        return (jiffies_64 - sched_clock_base) * (1000000000 / HZ);
+}
+
+static void lguest_load_esp0(struct tss_struct *tss,
+                                     struct thread_struct *thread)
+{
+        lazy_hcall(LHCALL_SET_STACK, __KERNEL_DS|0x1, thread->esp0,
+                   THREAD_SIZE/PAGE_SIZE);
+}
+
+static void lguest_set_debugreg(int regno, unsigned long value)
+{
+        /* FIXME: Implement */
+}
+
+static void lguest_wbinvd(void)
+{
+}
+
+#ifdef CONFIG_X86_LOCAL_APIC
+static void lguest_apic_write(unsigned long reg, unsigned long v)
+{
+}
+
+static unsigned long lguest_apic_read(unsigned long reg)
+{
+        return 0;
+}
+#endif
+
+static void lguest_safe_halt(void)
+{
+        hcall(LHCALL_HALT, 0, 0, 0);
+}
+
+static void lguest_power_off(void)
+{
+        hcall(LHCALL_CRASH, __pa("Power down"), 0, 0);
+}
+
+static int lguest_panic(struct notifier_block *nb, unsigned long l, void *p)
+{
+        hcall(LHCALL_CRASH, __pa(p), 0, 0);
+        return NOTIFY_DONE;
+}
+
+static struct notifier_block paniced = {
+        .notifier_call = lguest_panic
+};
+
+static __init char *lguest_memory_setup(void)
+{
+        /* We do this here because lockcheck barfs if before start_kernel */
+        atomic_notifier_chain_register(&panic_notifier_list, &paniced);
+
+        e820.nr_map = 0;
+        add_memory_region(0, PFN_PHYS(boot->max_pfn), E820_RAM);
+        return "LGUEST";
+}
+
+static const struct lguest_insns
+{
+        const char *start, *end;
+} lguest_insns[] = {
+        [PARAVIRT_PATCH(irq_disable)] = { lgstart_cli, lgend_cli },
+        [PARAVIRT_PATCH(irq_enable)] = { lgstart_sti, lgend_sti },
+        [PARAVIRT_PATCH(restore_fl)] = { lgstart_popf, lgend_popf },
+        [PARAVIRT_PATCH(save_fl)] = { lgstart_pushf, lgend_pushf },
+};
+static unsigned lguest_patch(u8 type, u16 clobber, void *insns, unsigned len)
+{
+        unsigned int insn_len;
+
+        /* Don't touch it if we don't have a replacement */
+        if (type >= ARRAY_SIZE(lguest_insns) || !lguest_insns[type].start)
+                return paravirt_patch_default(type, clobber, insns, len);
+
+        insn_len = lguest_insns[type].end - lguest_insns[type].start;
+
+        /* Similarly if we can't fit replacement. */
+        if (len < insn_len)
+                return paravirt_patch_default(type, clobber, insns, len);
+
+        memcpy(insns, lguest_insns[type].start, insn_len);
+        return insn_len;
+}
+
+__init void lguest_init(void)
+{
+        paravirt_ops.name = "lguest";
+        paravirt_ops.paravirt_enabled = 1;
+        paravirt_ops.kernel_rpl = 1;
+
+        paravirt_ops.save_fl = save_fl;
+        paravirt_ops.restore_fl = restore_fl;
+        paravirt_ops.irq_disable = irq_disable;
+        paravirt_ops.irq_enable = irq_enable;
+        paravirt_ops.load_gdt = lguest_load_gdt;
+        paravirt_ops.memory_setup = lguest_memory_setup;
+        paravirt_ops.cpuid = lguest_cpuid;
+        paravirt_ops.write_cr3 = lguest_write_cr3;
+        paravirt_ops.flush_tlb_user = lguest_flush_tlb_user;
+        paravirt_ops.flush_tlb_single = lguest_flush_tlb_single;
+        paravirt_ops.flush_tlb_kernel = lguest_flush_tlb_kernel;
+        paravirt_ops.set_pte = lguest_set_pte;
+        paravirt_ops.set_pte_at = lguest_set_pte_at;
+        paravirt_ops.set_pmd = lguest_set_pmd;
+#ifdef CONFIG_X86_LOCAL_APIC
+        paravirt_ops.apic_write = lguest_apic_write;
+        paravirt_ops.apic_write_atomic = lguest_apic_write;
+        paravirt_ops.apic_read = lguest_apic_read;
+#endif
+        paravirt_ops.load_idt = lguest_load_idt;
+        paravirt_ops.iret = lguest_iret;
+        paravirt_ops.load_esp0 = lguest_load_esp0;
+        paravirt_ops.load_tr_desc = lguest_load_tr_desc;
+        paravirt_ops.set_ldt = lguest_set_ldt;
+        paravirt_ops.load_tls = lguest_load_tls;
+        paravirt_ops.set_debugreg = lguest_set_debugreg;
+        paravirt_ops.clts = lguest_clts;
+        paravirt_ops.read_cr0 = lguest_read_cr0;
+        paravirt_ops.write_cr0 = lguest_write_cr0;
+        paravirt_ops.init_IRQ = lguest_init_IRQ;
+        paravirt_ops.read_cr2 = lguest_read_cr2;
+        paravirt_ops.read_cr3 = lguest_read_cr3;
+        paravirt_ops.read_cr4 = lguest_read_cr4;
+        paravirt_ops.write_cr4 = lguest_write_cr4;
+        paravirt_ops.write_gdt_entry = lguest_write_gdt_entry;
+        paravirt_ops.write_idt_entry = lguest_write_idt_entry;
+        paravirt_ops.patch = lguest_patch;
+        paravirt_ops.safe_halt = lguest_safe_halt;
+        paravirt_ops.get_wallclock = lguest_get_wallclock;
+        paravirt_ops.time_init = lguest_time_init;
+        paravirt_ops.set_lazy_mode = lguest_lazy_mode;
+        paravirt_ops.wbinvd = lguest_wbinvd;
+        paravirt_ops.sched_clock = lguest_sched_clock;
+
+        hcall(LHCALL_LGUEST_INIT, __pa(&lguest_data), 0, 0);
+        strncpy(boot_command_line, boot->cmdline, COMMAND_LINE_SIZE);
+
+        /* We use top of mem for initial pagetables. */
+        init_pg_tables_end = __pa(pg0);
+
+        asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_DS) : "memory");
+
+        reserve_top_address(lguest_data.reserve_mem);
+
+        lockdep_init();
+
+        paravirt_disable_iospace();
+
+        cpu_detect(&new_cpu_data);
+        /* head.S usually sets up the first capability word, so do it here. */
+        new_cpu_data.x86_capability[0] = cpuid_edx(1);
+
+        /* Math is always hard! */
+        new_cpu_data.hard_math = 1;
+
+#ifdef CONFIG_X86_MCE
+        mce_disabled = 1;
+#endif
+
+#ifdef CONFIG_ACPI
+        acpi_disabled = 1;
+        acpi_ht = 0;
+#endif
+
+        add_preferred_console("hvc", 0, NULL);
+
+        if (boot->initrd_size) {
+                /* We stash this at top of memory. */
+                INITRD_START = boot->max_pfn*PAGE_SIZE - boot->initrd_size;
+                INITRD_SIZE = boot->initrd_size;
+                LOADER_TYPE = 0xFF;
+        }
+
+        pm_power_off = lguest_power_off;
+        start_kernel();
+}