8 files changed, 111 insertions, 41 deletions

diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c
index 60156dfdc608..4845fb3cf74b 100644
--- a/drivers/lguest/core.c
+++ b/drivers/lguest/core.c
@@ -152,8 +152,8 @@ static void unmap_switcher(void)
  * code.  We have to check that the range is below the pfn_limit the Launcher
  * gave us.  We have to make sure that addr + len doesn't give us a false
  * positive by overflowing, too. */
-int lguest_address_ok(const struct lguest *lg,
-                      unsigned long addr, unsigned long len)
+bool lguest_address_ok(const struct lguest *lg,
+                       unsigned long addr, unsigned long len)
 {
         return (addr+len) / PAGE_SIZE < lg->pfn_limit && (addr+len >= addr);
 }
diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c
index 415fab0125ac..6e99adbe1946 100644
--- a/drivers/lguest/interrupts_and_traps.c
+++ b/drivers/lguest/interrupts_and_traps.c
@@ -34,7 +34,7 @@ static int idt_type(u32 lo, u32 hi)
 }
 
 /* An IDT entry can't be used unless the "present" bit is set. */
-static int idt_present(u32 lo, u32 hi)
+static bool idt_present(u32 lo, u32 hi)
 {
         return (hi & 0x8000);
 }
@@ -60,7 +60,8 @@ static void push_guest_stack(struct lg_cpu *cpu, unsigned long *gstack, u32 val)
  * We set up the stack just like the CPU does for a real interrupt, so it's
  * identical for the Guest (and the standard "iret" instruction will undo
  * it). */
-static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi, int has_err)
+static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi,
+                                bool has_err)
 {
         unsigned long gstack, origstack;
         u32 eflags, ss, irq_enable;
@@ -184,7 +185,7 @@ void maybe_do_interrupt(struct lg_cpu *cpu)
                 /* set_guest_interrupt() takes the interrupt descriptor and a
                  * flag to say whether this interrupt pushes an error code onto
                  * the stack as well: virtual interrupts never do. */
-                set_guest_interrupt(cpu, idt->a, idt->b, 0);
+                set_guest_interrupt(cpu, idt->a, idt->b, false);
         }
 
         /* Every time we deliver an interrupt, we update the timestamp in the
@@ -244,26 +245,26 @@ void free_interrupts(void)
 /*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)
+static bool has_err(unsigned int trap)
 {
         return (trap == 8 || (trap >= 10 && trap <= 14) || trap == 17);
 }
 
 /* deliver_trap() returns true if it could deliver the trap. */
-int deliver_trap(struct lg_cpu *cpu, unsigned int num)
+bool deliver_trap(struct lg_cpu *cpu, unsigned int num)
 {
         /* Trap numbers are always 8 bit, but we set an impossible trap number
          * for traps inside the Switcher, so check that here. */
         if (num >= ARRAY_SIZE(cpu->arch.idt))
-                return 0;
+                return false;
 
         /* Early on the Guest hasn't set the IDT entries (or maybe it put a
          * bogus one in): if we fail here, the Guest will be killed. */
         if (!idt_present(cpu->arch.idt[num].a, cpu->arch.idt[num].b))
-                return 0;
+                return false;
         set_guest_interrupt(cpu, cpu->arch.idt[num].a,
                             cpu->arch.idt[num].b, has_err(num));
-        return 1;
+        return true;
 }
 
 /*H:250 Here's the hard part: returning to the Host every time a trap happens
@@ -279,18 +280,19 @@ int deliver_trap(struct lg_cpu *cpu, unsigned int num)
  *
  * This routine indicates if a particular trap number could be delivered
  * directly. */
-static int direct_trap(unsigned int num)
+static bool direct_trap(unsigned int num)
 {
         /* Hardware interrupts don't go to the Guest at all (except system
          * call). */
         if (num >= FIRST_EXTERNAL_VECTOR && !could_be_syscall(num))
-                return 0;
+                return false;
 
         /* The Host needs to see page faults (for shadow paging and to save the
          * fault address), general protection faults (in/out emulation) and
-         * device not available (TS handling), and of course, the hypercall
-         * trap. */
-        return num != 14 && num != 13 && num != 7 && num != LGUEST_TRAP_ENTRY;
+         * device not available (TS handling), invalid opcode fault (kvm hcall),
+         * and of course, the hypercall trap. */
+        return num != 14 && num != 13 && num != 7 &&
+                        num != 6 && num != LGUEST_TRAP_ENTRY;
 }
 /*:*/
 
diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h
index f2c641e0bdde..ac8a4a3741b8 100644
--- a/drivers/lguest/lg.h
+++ b/drivers/lguest/lg.h
@@ -109,8 +109,8 @@ struct lguest
 extern struct mutex lguest_lock;
 
 /* core.c: */
-int lguest_address_ok(const struct lguest *lg,
-                      unsigned long addr, unsigned long len);
+bool lguest_address_ok(const struct lguest *lg,
+                       unsigned long addr, unsigned long len);
 void __lgread(struct lg_cpu *, void *, unsigned long, unsigned);
 void __lgwrite(struct lg_cpu *, unsigned long, const void *, unsigned);
 
@@ -140,7 +140,7 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user);
 
 /* interrupts_and_traps.c: */
 void maybe_do_interrupt(struct lg_cpu *cpu);
-int deliver_trap(struct lg_cpu *cpu, unsigned int num);
+bool deliver_trap(struct lg_cpu *cpu, unsigned int num);
 void load_guest_idt_entry(struct lg_cpu *cpu, unsigned int i,
                           u32 low, u32 hi);
 void guest_set_stack(struct lg_cpu *cpu, u32 seg, u32 esp, unsigned int pages);
@@ -173,7 +173,7 @@ void guest_pagetable_flush_user(struct lg_cpu *cpu);
 void guest_set_pte(struct lg_cpu *cpu, unsigned long gpgdir,
                    unsigned long vaddr, pte_t val);
 void map_switcher_in_guest(struct lg_cpu *cpu, struct lguest_pages *pages);
-int demand_page(struct lg_cpu *cpu, unsigned long cr2, int errcode);
+bool demand_page(struct lg_cpu *cpu, unsigned long cr2, int errcode);
 void pin_page(struct lg_cpu *cpu, unsigned long vaddr);
 unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr);
 void page_table_guest_data_init(struct lg_cpu *cpu);
diff --git a/drivers/lguest/lguest_device.c b/drivers/lguest/lguest_device.c
index 8132533d71f9..df44d962626d 100644
--- a/drivers/lguest/lguest_device.c
+++ b/drivers/lguest/lguest_device.c
@@ -161,7 +161,7 @@ static void set_status(struct virtio_device *vdev, u8 status)
 
         /* We set the status. */
         to_lgdev(vdev)->desc->status = status;
-        hcall(LHCALL_NOTIFY, (max_pfn<<PAGE_SHIFT) + offset, 0, 0);
+        kvm_hypercall1(LHCALL_NOTIFY, (max_pfn << PAGE_SHIFT) + offset);
 }
 
 static void lg_set_status(struct virtio_device *vdev, u8 status)
@@ -209,7 +209,7 @@ static void lg_notify(struct virtqueue *vq)
          * virtqueue structure. */
         struct lguest_vq_info *lvq = vq->priv;
 
-        hcall(LHCALL_NOTIFY, lvq->config.pfn << PAGE_SHIFT, 0, 0);
+        kvm_hypercall1(LHCALL_NOTIFY, lvq->config.pfn << PAGE_SHIFT);
 }
 
 /* An extern declaration inside a C file is bad form.  Don't do it. */
diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c
index 576a8318221c..a059cf9980f7 100644
--- a/drivers/lguest/page_tables.c
+++ b/drivers/lguest/page_tables.c
@@ -199,7 +199,7 @@ static void check_gpgd(struct lg_cpu *cpu, pgd_t gpgd)
  *
  * If we fixed up the fault (ie. we mapped the address), this routine returns
  * true.  Otherwise, it was a real fault and we need to tell the Guest. */
-int demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
+bool demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
 {
         pgd_t gpgd;
         pgd_t *spgd;
@@ -211,7 +211,7 @@ int demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
         gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t);
         /* Toplevel not present?  We can't map it in. */
         if (!(pgd_flags(gpgd) & _PAGE_PRESENT))
-                return 0;
+                return false;
 
         /* Now look at the matching shadow entry. */
         spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr);
@@ -222,7 +222,7 @@ int demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
                  * simple for this corner case. */
                 if (!ptepage) {
                         kill_guest(cpu, "out of memory allocating pte page");
-                        return 0;
+                        return false;
                 }
                 /* We check that the Guest pgd is OK. */
                 check_gpgd(cpu, gpgd);
@@ -238,16 +238,16 @@ int demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
 
         /* If this page isn't in the Guest page tables, we can't page it in. */
         if (!(pte_flags(gpte) & _PAGE_PRESENT))
-                return 0;
+                return false;
 
         /* Check they're not trying to write to a page the Guest wants
          * read-only (bit 2 of errcode == write). */
         if ((errcode & 2) && !(pte_flags(gpte) & _PAGE_RW))
-                return 0;
+                return false;
 
         /* User access to a kernel-only page? (bit 3 == user access) */
         if ((errcode & 4) && !(pte_flags(gpte) & _PAGE_USER))
-                return 0;
+                return false;
 
         /* Check that the Guest PTE flags are OK, and the page number is below
          * the pfn_limit (ie. not mapping the Launcher binary). */
@@ -283,7 +283,7 @@ int demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
          * manipulated, the result returned and the code complete.  A small
          * delay and a trace of alliteration are the only indications the Guest
          * has that a page fault occurred at all. */
-        return 1;
+        return true;
 }
 
 /*H:360
@@ -296,7 +296,7 @@ int demand_page(struct lg_cpu *cpu, unsigned long vaddr, int errcode)
  *
  * This is a quick version which answers the question: is this virtual address
  * mapped by the shadow page tables, and is it writable? */
-static int page_writable(struct lg_cpu *cpu, unsigned long vaddr)
+static bool page_writable(struct lg_cpu *cpu, unsigned long vaddr)
 {
         pgd_t *spgd;
         unsigned long flags;
@@ -304,7 +304,7 @@ static int page_writable(struct lg_cpu *cpu, unsigned long vaddr)
         /* Look at the current top level entry: is it present? */
         spgd = spgd_addr(cpu, cpu->cpu_pgd, vaddr);
         if (!(pgd_flags(*spgd) & _PAGE_PRESENT))
-                return 0;
+                return false;
 
         /* Check the flags on the pte entry itself: it must be present and
          * writable. */
@@ -373,8 +373,10 @@ unsigned long guest_pa(struct lg_cpu *cpu, unsigned long vaddr)
         /* First step: get the top-level Guest page table entry. */
         gpgd = lgread(cpu, gpgd_addr(cpu, vaddr), pgd_t);
         /* Toplevel not present?  We can't map it in. */
-        if (!(pgd_flags(gpgd) & _PAGE_PRESENT))
+        if (!(pgd_flags(gpgd) & _PAGE_PRESENT)) {
                 kill_guest(cpu, "Bad address %#lx", vaddr);
+                return -1UL;
+        }
 
         gpte = lgread(cpu, gpte_addr(gpgd, vaddr), pte_t);
         if (!(pte_flags(gpte) & _PAGE_PRESENT))
diff --git a/drivers/lguest/segments.c b/drivers/lguest/segments.c
index ec6aa3f1c36b..4f15439b7f12 100644
--- a/drivers/lguest/segments.c
+++ b/drivers/lguest/segments.c
@@ -45,7 +45,7 @@
  * "Task State Segment" which controls all kinds of delicate things.  The
  * LGUEST_CS and LGUEST_DS entries are reserved for the Switcher, and the
  * the Guest can't be trusted to deal with double faults. */
-static int ignored_gdt(unsigned int num)
+static bool ignored_gdt(unsigned int num)
 {
         return (num == GDT_ENTRY_TSS
                 || num == GDT_ENTRY_LGUEST_CS
diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c
index bf7942327bda..a6b717644be0 100644
--- a/drivers/lguest/x86/core.c
+++ b/drivers/lguest/x86/core.c
@@ -290,6 +290,57 @@ static int emulate_insn(struct lg_cpu *cpu)
         return 1;
 }
 
+/* Our hypercalls mechanism used to be based on direct software interrupts.
+ * After Anthony's "Refactor hypercall infrastructure" kvm patch, we decided to
+ * change over to using kvm hypercalls.
+ *
+ * KVM_HYPERCALL is actually a "vmcall" instruction, which generates an invalid
+ * opcode fault (fault 6) on non-VT cpus, so the easiest solution seemed to be
+ * an *emulation approach*: if the fault was really produced by an hypercall
+ * (is_hypercall() does exactly this check), we can just call the corresponding
+ * hypercall host implementation function.
+ *
+ * But these invalid opcode faults are notably slower than software interrupts.
+ * So we implemented the *patching (or rewriting) approach*: every time we hit
+ * the KVM_HYPERCALL opcode in Guest code, we patch it to the old "int 0x1f"
+ * opcode, so next time the Guest calls this hypercall it will use the
+ * faster trap mechanism.
+ *
+ * Matias even benchmarked it to convince you: this shows the average cycle
+ * cost of a hypercall.  For each alternative solution mentioned above we've
+ * made 5 runs of the benchmark:
+ *
+ * 1) direct software interrupt: 2915, 2789, 2764, 2721, 2898
+ * 2) emulation technique: 3410, 3681, 3466, 3392, 3780
+ * 3) patching (rewrite) technique: 2977, 2975, 2891, 2637, 2884
+ *
+ * One two-line function is worth a 20% hypercall speed boost!
+ */
+static void rewrite_hypercall(struct lg_cpu *cpu)
+{
+        /* This are the opcodes we use to patch the Guest.  The opcode for "int
+         * $0x1f" is "0xcd 0x1f" but vmcall instruction is 3 bytes long, so we
+         * complete the sequence with a NOP (0x90). */
+        u8 insn[3] = {0xcd, 0x1f, 0x90};
+
+        __lgwrite(cpu, guest_pa(cpu, cpu->regs->eip), insn, sizeof(insn));
+}
+
+static bool is_hypercall(struct lg_cpu *cpu)
+{
+        u8 insn[3];
+
+        /* This must be the Guest kernel trying to do something.
+         * The bottom two bits of the CS segment register are the privilege
+         * level. */
+        if ((cpu->regs->cs & 3) != GUEST_PL)
+                return false;
+
+        /* Is it a vmcall? */
+        __lgread(cpu, insn, guest_pa(cpu, cpu->regs->eip), sizeof(insn));
+        return insn[0] == 0x0f && insn[1] == 0x01 && insn[2] == 0xc1;
+}
+
 /*H:050 Once we've re-enabled interrupts, we look at why the Guest exited. */
 void lguest_arch_handle_trap(struct lg_cpu *cpu)
 {
@@ -337,7 +388,7 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
                 break;
         case 32 ... 255:
                 /* These values mean a real interrupt occurred, in which case
-                 * the Host handler has already been run.  We just do a
+                 * the Host handler has already been run. We just do a
                  * friendly check if another process should now be run, then
                  * return to run the Guest again */
                 cond_resched();
@@ -347,6 +398,15 @@ void lguest_arch_handle_trap(struct lg_cpu *cpu)
                  * up the pointer now to indicate a hypercall is pending. */
                 cpu->hcall = (struct hcall_args *)cpu->regs;
                 return;
+        case 6:
+                /* kvm hypercalls trigger an invalid opcode fault (6).
+                 * We need to check if ring == GUEST_PL and
+                 * faulting instruction == vmcall. */
+                if (is_hypercall(cpu)) {
+                        rewrite_hypercall(cpu);
+                        return;
+                }
+                break;
         }
 
         /* We didn't handle the trap, so it needs to go to the Guest. */
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 5777196bf6c9..5c52369ab9bb 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -23,15 +23,21 @@
 
 #ifdef DEBUG
 /* For development, we want to crash whenever the ring is screwed. */
-#define BAD_RING(vq, fmt...)                    \
-        do { dev_err(&vq->vq.vdev->dev, fmt); BUG(); } while(0)
-#define START_USE(vq) \
-        do { if ((vq)->in_use) panic("in_use = %i\n", (vq)->in_use); (vq)->in_use = __LINE__; mb(); } while(0)
-#define END_USE(vq) \
-        do { BUG_ON(!(vq)->in_use); (vq)->in_use = 0; mb(); } while(0)
+#define BAD_RING(_vq, fmt...)                   \
+        do { dev_err(&(_vq)->vq.vdev->dev, fmt); BUG(); } while(0)
+/* Caller is supposed to guarantee no reentry. */
+#define START_USE(_vq)                                          \
+        do {                                                    \
+                if ((_vq)->in_use)                              \
+                        panic("in_use = %i\n", (_vq)->in_use);  \
+                (_vq)->in_use = __LINE__;                       \
+                mb();                                           \
+        } while(0)
+#define END_USE(_vq) \
+        do { BUG_ON(!(_vq)->in_use); (_vq)->in_use = 0; mb(); } while(0)
 #else
-#define BAD_RING(vq, fmt...)                    \
-        do { dev_err(&vq->vq.vdev->dev, fmt); (vq)->broken = true; } while(0)
+#define BAD_RING(_vq, fmt...)                   \
+        do { dev_err(&_vq->vq.vdev->dev, fmt); (_vq)->broken = true; } while(0)
 #define START_USE(vq)
 #define END_USE(vq)
 #endif