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authorLinus Torvalds <torvalds@linux-foundation.org>2015-04-22 10:55:06 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-22 10:55:06 -0700
commitb9bb6fb73b3e112d241a5edd146740be9a0c3cc0 (patch)
treed65072d0371468d685b7464dc6b38f920c0c9666 /drivers/lguest
parent15ce2658ddbd3db20dfba3622f3d224f01837fdc (diff)
parent9abbfb486f5c254805bb6a3f263bc14d989eb90b (diff)
Merge tag 'virtio-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux
Pull virtio updates from Rusty Russell: "Some virtio internal cleanups, a new virtio device "virtio input", and a change to allow the legacy virtio balloon. Most excitingly, some lguest work! No seriously, I got some cleanup patches" * tag 'virtio-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux: virtio: drop virtio_device_is_legacy_only virtio_pci: support non-legacy balloon devices virtio_mmio: support non-legacy balloon devices virtio_ccw: support non-legacy balloon devices virtio: balloon might not be a legacy device virtio_balloon: transitional interface virtio_ring: Update weak barriers to use dma_wmb/rmb virtio_pci_modern: switch to type-safe io accessors virtio_pci_modern: type-safe io accessors lguest: handle traps on the "interrupt suppressed" iret instruction. virtio: drop a useless config read virtio_config: reorder functions Add virtio-input driver. lguest: suppress interrupts for single insn, not range. lguest: simplify lguest_iret lguest: rename i386_head.S in the comments lguest: explicitly set miscdevice's private_data NULL lguest: fix pending interrupt test.
Diffstat (limited to 'drivers/lguest')
-rw-r--r--drivers/lguest/hypercalls.c5
-rw-r--r--drivers/lguest/interrupts_and_traps.c105
-rw-r--r--drivers/lguest/lg.h2
-rw-r--r--drivers/lguest/lguest_user.c8
4 files changed, 86 insertions, 34 deletions
diff --git a/drivers/lguest/hypercalls.c b/drivers/lguest/hypercalls.c
index 1219af493c0f..19a32280731d 100644
--- a/drivers/lguest/hypercalls.c
+++ b/drivers/lguest/hypercalls.c
@@ -211,10 +211,9 @@ static void initialize(struct lg_cpu *cpu)
/*
* The Guest tells us where we're not to deliver interrupts by putting
- * the range of addresses into "struct lguest_data".
+ * the instruction address into "struct lguest_data".
*/
- if (get_user(cpu->lg->noirq_start, &cpu->lg->lguest_data->noirq_start)
- || get_user(cpu->lg->noirq_end, &cpu->lg->lguest_data->noirq_end))
+ if (get_user(cpu->lg->noirq_iret, &cpu->lg->lguest_data->noirq_iret))
kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
/*
diff --git a/drivers/lguest/interrupts_and_traps.c b/drivers/lguest/interrupts_and_traps.c
index 70dfcdc29f1f..5e7559be222a 100644
--- a/drivers/lguest/interrupts_and_traps.c
+++ b/drivers/lguest/interrupts_and_traps.c
@@ -56,21 +56,16 @@ static void push_guest_stack(struct lg_cpu *cpu, unsigned long *gstack, u32 val)
}
/*H:210
- * The set_guest_interrupt() routine actually delivers the interrupt or
- * trap. The mechanics of delivering traps and interrupts to the Guest are the
- * same, except some traps have an "error code" which gets pushed onto the
- * stack as well: the caller tells us if this is one.
- *
- * "lo" and "hi" are the two parts of the Interrupt Descriptor Table for this
- * interrupt or trap. It's split into two parts for traditional reasons: gcc
- * on i386 used to be frightened by 64 bit numbers.
+ * The push_guest_interrupt_stack() routine saves Guest state on the stack for
+ * an interrupt or trap. The mechanics of delivering traps and interrupts to
+ * the Guest are the same, except some traps have an "error code" which gets
+ * pushed onto the stack as well: the caller tells us if this is one.
*
* 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,
- bool has_err)
+static void push_guest_interrupt_stack(struct lg_cpu *cpu, bool has_err)
{
unsigned long gstack, origstack;
u32 eflags, ss, irq_enable;
@@ -130,12 +125,28 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi,
if (has_err)
push_guest_stack(cpu, &gstack, cpu->regs->errcode);
- /*
- * Now we've pushed all the old state, we change the stack, the code
- * segment and the address to execute.
- */
+ /* Adjust the stack pointer and stack segment. */
cpu->regs->ss = ss;
cpu->regs->esp = virtstack + (gstack - origstack);
+}
+
+/*
+ * This actually makes the Guest start executing the given interrupt/trap
+ * handler.
+ *
+ * "lo" and "hi" are the two parts of the Interrupt Descriptor Table for this
+ * interrupt or trap. It's split into two parts for traditional reasons: gcc
+ * on i386 used to be frightened by 64 bit numbers.
+ */
+static void guest_run_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi)
+{
+ /* If we're already in the kernel, we don't change stacks. */
+ if ((cpu->regs->ss&0x3) != GUEST_PL)
+ cpu->regs->ss = cpu->esp1;
+
+ /*
+ * Set the code segment and the address to execute.
+ */
cpu->regs->cs = (__KERNEL_CS|GUEST_PL);
cpu->regs->eip = idt_address(lo, hi);
@@ -158,6 +169,24 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi,
kill_guest(cpu, "Disabling interrupts");
}
+/* This restores the eflags word which was pushed on the stack by a trap */
+static void restore_eflags(struct lg_cpu *cpu)
+{
+ /* This is the physical address of the stack. */
+ unsigned long stack_pa = guest_pa(cpu, cpu->regs->esp);
+
+ /*
+ * Stack looks like this:
+ * Address Contents
+ * esp EIP
+ * esp + 4 CS
+ * esp + 8 EFLAGS
+ */
+ cpu->regs->eflags = lgread(cpu, stack_pa + 8, u32);
+ cpu->regs->eflags &=
+ ~(X86_EFLAGS_TF|X86_EFLAGS_VM|X86_EFLAGS_RF|X86_EFLAGS_NT);
+}
+
/*H:205
* Virtual Interrupts.
*
@@ -200,14 +229,6 @@ void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more)
BUG_ON(irq >= LGUEST_IRQS);
- /*
- * They may be in the middle of an iret, where they asked us never to
- * deliver interrupts.
- */
- if (cpu->regs->eip >= cpu->lg->noirq_start &&
- (cpu->regs->eip < cpu->lg->noirq_end))
- return;
-
/* If they're halted, interrupts restart them. */
if (cpu->halted) {
/* Re-enable interrupts. */
@@ -237,12 +258,34 @@ void try_deliver_interrupt(struct lg_cpu *cpu, unsigned int irq, bool more)
if (idt_present(idt->a, idt->b)) {
/* OK, mark it no longer pending and deliver it. */
clear_bit(irq, cpu->irqs_pending);
+
/*
- * 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.
+ * They may be about to iret, where they asked us never to
+ * deliver interrupts. In this case, we can emulate that iret
+ * then immediately deliver the interrupt. This is basically
+ * a noop: the iret would pop the interrupt frame and restore
+ * eflags, and then we'd set it up again. So just restore the
+ * eflags word and jump straight to the handler in this case.
+ *
+ * Denys Vlasenko points out that this isn't quite right: if
+ * the iret was returning to userspace, then that interrupt
+ * would reset the stack pointer (which the Guest told us
+ * about via LHCALL_SET_STACK). But unless the Guest is being
+ * *really* weird, that will be the same as the current stack
+ * anyway.
*/
- set_guest_interrupt(cpu, idt->a, idt->b, false);
+ if (cpu->regs->eip == cpu->lg->noirq_iret) {
+ restore_eflags(cpu);
+ } else {
+ /*
+ * set_guest_interrupt() takes a flag to say whether
+ * this interrupt pushes an error code onto the stack
+ * as well: virtual interrupts never do.
+ */
+ push_guest_interrupt_stack(cpu, false);
+ }
+ /* Actually make Guest cpu jump to handler. */
+ guest_run_interrupt(cpu, idt->a, idt->b);
}
/*
@@ -353,8 +396,9 @@ bool deliver_trap(struct lg_cpu *cpu, unsigned int num)
*/
if (!idt_present(cpu->arch.idt[num].a, cpu->arch.idt[num].b))
return false;
- set_guest_interrupt(cpu, cpu->arch.idt[num].a,
- cpu->arch.idt[num].b, has_err(num));
+ push_guest_interrupt_stack(cpu, has_err(num));
+ guest_run_interrupt(cpu, cpu->arch.idt[num].a,
+ cpu->arch.idt[num].b);
return true;
}
@@ -395,8 +439,9 @@ static bool direct_trap(unsigned int num)
* The Guest has the ability to turn its interrupt gates into trap gates,
* if it is careful. The Host will let trap gates can go directly to the
* Guest, but the Guest needs the interrupts atomically disabled for an
- * interrupt gate. It can do this by pointing the trap gate at instructions
- * within noirq_start and noirq_end, where it can safely disable interrupts.
+ * interrupt gate. The Host could provide a mechanism to register more
+ * "no-interrupt" regions, and the Guest could point the trap gate at
+ * instructions within that region, where it can safely disable interrupts.
*/
/*M:006
diff --git a/drivers/lguest/lg.h b/drivers/lguest/lg.h
index 307e8b39e7d1..ac8ad0461e80 100644
--- a/drivers/lguest/lg.h
+++ b/drivers/lguest/lg.h
@@ -102,7 +102,7 @@ struct lguest {
struct pgdir pgdirs[4];
- unsigned long noirq_start, noirq_end;
+ unsigned long noirq_iret;
unsigned int stack_pages;
u32 tsc_khz;
diff --git a/drivers/lguest/lguest_user.c b/drivers/lguest/lguest_user.c
index c4c6113eb9a6..30c60687d277 100644
--- a/drivers/lguest/lguest_user.c
+++ b/drivers/lguest/lguest_user.c
@@ -339,6 +339,13 @@ static ssize_t write(struct file *file, const char __user *in,
}
}
+static int open(struct inode *inode, struct file *file)
+{
+ file->private_data = NULL;
+
+ return 0;
+}
+
/*L:060
* The final piece of interface code is the close() routine. It reverses
* everything done in initialize(). This is usually called because the
@@ -409,6 +416,7 @@ static int close(struct inode *inode, struct file *file)
*/
static const struct file_operations lguest_fops = {
.owner = THIS_MODULE,
+ .open = open,
.release = close,
.write = write,
.read = read,