Re: [PATCH] Support for in-kernel mmio handlers

Gregory Haskins
2007-04-09T14:14:42Z

Hi Avi,

I believe I have incorporated all of the changes requested. Please find the result of that patch inline.

Note that I finally understand what you were getting at with the array of objects thing. I didn't change it yet for the same reason that you mentioned: reduction of churn. However, now that I understand it, I see why you wanted it. Perhaps I will send a follow-on to this patch that uses your idea. But for now...

---

KVM: Add support for in-kernel mmio handlers

There is a near-term need for moving some of the emulation from userspace to
the kernel (e.g. interrupt handling). This patch adds a construct for
registering in-kernel MMIO handlers. The consumers of this interface will
appear in a follow-on patch.

Signed-off-by: Gregory Haskins <ghaskins-Et1tbQHTxzrQT0dZR+AlfA@public.gmane.org>

---

drivers/kvm/kvm.h | 31 ++++++++++++++++++
drivers/kvm/kvm_main.c | 82 +++++++++++++++++++++++++++++++++++++++++-------
2 files changed, 101 insertions(+), 12 deletions(-)

diff --git a/drivers/kvm/kvm.h b/drivers/kvm/kvm.h
index fceeb84..181099f 100644
--- a/drivers/kvm/kvm.h
+++ b/drivers/kvm/kvm.h
@@ -236,6 +236,36 @@ struct kvm_pio_request {
int rep;
};

+struct kvm_io_device {
+ unsigned long (*read)(struct kvm_io_device *this,
+ gpa_t addr,
+ int length);
+ void (*write)(struct kvm_io_device *this,
+ gpa_t addr,
+ int length,
+ unsigned long val);
+ int (*in_range)(struct kvm_io_device *this, gpa_t addr);
+
+ void *private;
+};
+
+/*
+ * It would be nice to use something smarter than a linear search, TBD...
+ * Thankfully we dont expect many devices to register (famous last words :),
+ * so until then it will suffice. At least its abstracted so we can change
+ * in one place.
+ */
+struct kvm_io_bus {
+ int dev_count;
+#define NR_IOBUS_DEVS 6
+ struct kvm_io_device *devs[NR_IOBUS_DEVS];
+};
+
+void kvm_io_bus_init(struct kvm_io_bus *bus);
+struct kvm_io_device *kvm_io_bus_find_dev(struct kvm_io_bus *bus, gpa_t addr);
+void kvm_io_bus_register_dev(struct kvm_io_bus *bus,
+ struct kvm_io_device *dev);
+
struct kvm_vcpu {
struct kvm *kvm;
union {
@@ -345,6 +375,7 @@ struct kvm {
unsigned long rmap_overflow;
struct list_head vm_list;
struct file *filp;
+ struct kvm_io_bus mmio_bus;
};

struct kvm_stat {
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 4473174..c3c0059 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -294,6 +294,7 @@ static struct kvm *kvm_create_vm(void)

spin_lock_init(&kvm->lock);
INIT_LIST_HEAD(&kvm->active_mmu_pages);
+ kvm_io_bus_init(&kvm->mmio_bus);
for (i = 0; i < KVM_MAX_VCPUS; ++i) {
struct kvm_vcpu *vcpu = &kvm->vcpus[i];

@@ -1015,12 +1016,25 @@ static int emulator_write_std(unsigned long addr,
return X86EMUL_UNHANDLEABLE;
}

+static struct kvm_io_device *vcpu_find_mmio_dev(struct kvm_vcpu *vcpu,
+ gpa_t addr)
+{
+ /*
+ * Note that its important to have this wrapper function because
+ * in the very near future we will be checking for MMIOs against
+ * the LAPIC as well as the general MMIO bus
+ */
+ return kvm_io_bus_find_dev(&vcpu->kvm->mmio_bus, addr);
+}
+
static int emulator_read_emulated(unsigned long addr,
unsigned long *val,
unsigned int bytes,
struct x86_emulate_ctxt *ctxt)
{
- struct kvm_vcpu *vcpu = ctxt->vcpu;
+ struct kvm_vcpu *vcpu = ctxt->vcpu;
+ struct kvm_io_device *mmio_dev;
+ gpa_t gpa;

if (vcpu->mmio_read_completed) {
memcpy(val, vcpu->mmio_data, bytes);
@@ -1029,18 +1043,26 @@ static int emulator_read_emulated(unsigned long addr,
} else if (emulator_read_std(addr, val, bytes, ctxt)
== X86EMUL_CONTINUE)
return X86EMUL_CONTINUE;
- else {
- gpa_t gpa = vcpu->mmu.gva_to_gpa(vcpu, addr);

- if (gpa == UNMAPPED_GVA)
- return X86EMUL_PROPAGATE_FAULT;
- vcpu->mmio_needed = 1;
- vcpu->mmio_phys_addr = gpa;
- vcpu->mmio_size = bytes;
- vcpu->mmio_is_write = 0;
+ gpa = vcpu->mmu.gva_to_gpa(vcpu, addr);
+ if (gpa == UNMAPPED_GVA)
+ return X86EMUL_PROPAGATE_FAULT;

- return X86EMUL_UNHANDLEABLE;
+ /*
+ * Is this MMIO handled locally?
+ */
+ mmio_dev = vcpu_find_mmio_dev(vcpu, gpa);
+ if (mmio_dev) {
+ *val = mmio_dev->read(mmio_dev, gpa, bytes);
+ return X86EMUL_CONTINUE;
}
+
+ vcpu->mmio_needed = 1;
+ vcpu->mmio_phys_addr = gpa;
+ vcpu->mmio_size = bytes;
+ vcpu->mmio_is_write = 0;
+
+ return X86EMUL_UNHANDLEABLE;
}

static int emulator_write_phys(struct kvm_vcpu *vcpu, gpa_t gpa,
@@ -1068,8 +1090,9 @@ static int emulator_write_emulated(unsigned long addr,
unsigned int bytes,
struct x86_emulate_ctxt *ctxt)
{
- struct kvm_vcpu *vcpu = ctxt->vcpu;
- gpa_t gpa = vcpu->mmu.gva_to_gpa(vcpu, addr);
+ struct kvm_vcpu *vcpu = ctxt->vcpu;
+ struct kvm_io_device *mmio_dev;
+ gpa_t gpa = vcpu->mmu.gva_to_gpa(vcpu, addr);

if (gpa == UNMAPPED_GVA)
return X86EMUL_PROPAGATE_FAULT;
@@ -1077,6 +1100,15 @@ static int emulator_write_emulated(unsigned long addr,
if (emulator_write_phys(vcpu, gpa, val, bytes))
return X86EMUL_CONTINUE;

+ /*
+ * Is this MMIO handled locally?
+ */
+ mmio_dev = vcpu_find_mmio_dev(vcpu, gpa);
+ if (mmio_dev) {
+ mmio_dev->write(mmio_dev, gpa, bytes, val);
+ return X86EMUL_CONTINUE;
+ }
+
vcpu->mmio_needed = 1;
vcpu->mmio_phys_addr = gpa;
vcpu->mmio_size = bytes;
@@ -2911,6 +2943,32 @@ static int kvm_cpu_hotplug(struct notifier_block *notifier, unsigned long val,
return NOTIFY_OK;
}

+void kvm_io_bus_init(struct kvm_io_bus *bus)
+{
+ memset(bus, 0, sizeof(*bus));
+}
+
+struct kvm_io_device *kvm_io_bus_find_dev(struct kvm_io_bus *bus, gpa_t addr)
+{
+ int i;
+
+ for (i = 0; i < bus->dev_count; i++) {
+ struct kvm_io_device *pos = bus->devs[i];
+
+ if (pos->in_range(pos, addr))
+ return pos;
+ }
+
+ return NULL;
+}
+
+void kvm_io_bus_register_dev(struct kvm_io_bus *bus, struct kvm_io_device *dev)
+{
+ BUG_ON(bus->dev_count >= (NR_IOBUS_DEVS-1));
+
+ bus->devs[bus->dev_count++] = dev;
+}
+
static struct notifier_block kvm_cpu_notifier = {
.notifier_call = kvm_cpu_hotplug,
.priority = 20, /* must be > scheduler priority */