Re: [PATCH] kvm: remove in_range from kvm_io_device

Gregory Haskins
2009-06-23T15:22:18Z

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Michael S. Tsirkin wrote:
> Remove in_range from kvm_io_device and ask read/write callbacks, if
> supplied, to perform range checks internally. This allows aliasing
> (mostly for in-kernel virtio), as well as better error handling by
> making it possible to pass errors up to userspace. And it's enough to
> look at the diffstat to see that it's a better API anyway.
>
> While we are at it, document locking rules for kvm_io_device.
>

Sorry, not trying to be a PITA, but I liked your last suggestion better. :(

I am thinking forward to when we want to use something smarter than a
linear search (like rbtree/radix) for scaling the number of "devices"
(really, virtio-rings) that we support. The current device-count
target is 512, which we will begin to rapidly consume as the in-kernel
virtio work progresses. This proposed approach forces us into a
potential O(256) algorithm in the hotpath (all MMIO/PIO exits will hit
this, not just in-kernel users). How would you address this?

Regards,
-Greg

> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>
> This is a replacement for my patch extending in_range.
> This works for me, but please review carefully.
>
> arch/ia64/kvm/kvm-ia64.c | 28 ++++---------
> arch/x86/kvm/i8254.c | 49 ++++++++++++----------
> arch/x86/kvm/i8259.c | 22 ++++++----
> arch/x86/kvm/lapic.c | 48 ++++++++++------------
> arch/x86/kvm/x86.c | 100 +++++++++++++++------------------------------
> include/linux/kvm_host.h | 6 ++-
> virt/kvm/coalesced_mmio.c | 26 +++++-------
> virt/kvm/ioapic.c | 24 ++++++-----
> virt/kvm/iodev.h | 34 ++++++---------
> virt/kvm/kvm_main.c | 25 +++++++-----
> 10 files changed, 158 insertions(+), 204 deletions(-)
>
> diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
> index d20a5db..647ff91 100644
> --- a/arch/ia64/kvm/kvm-ia64.c
> +++ b/arch/ia64/kvm/kvm-ia64.c
> @@ -198,16 +198,6 @@ int kvm_dev_ioctl_check_extension(long ext)
>
> }
>
> -static struct kvm_io_device *vcpu_find_mmio_dev(struct kvm_vcpu *vcpu,
> - gpa_t addr, int len, int is_write)
> -{
> - struct kvm_io_device *dev;
> -
> - dev = kvm_io_bus_find_dev(&vcpu->kvm->mmio_bus, addr, len, is_write);
> -
> - return dev;
> -}
> -
> static int handle_vm_error(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> {
> kvm_run->exit_reason = KVM_EXIT_UNKNOWN;
> @@ -219,6 +209,7 @@ static int handle_mmio(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> {
> struct kvm_mmio_req *p;
> struct kvm_io_device *mmio_dev;
> + int r;
>
> p = kvm_get_vcpu_ioreq(vcpu);
>
> @@ -235,16 +226,13 @@ static int handle_mmio(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
> kvm_run->exit_reason = KVM_EXIT_MMIO;
> return 0;
> mmio:
> - mmio_dev = vcpu_find_mmio_dev(vcpu, p->addr, p->size, !p->dir);
> - if (mmio_dev) {
> - if (!p->dir)
> - kvm_iodevice_write(mmio_dev, p->addr, p->size,
> - &p->data);
> - else
> - kvm_iodevice_read(mmio_dev, p->addr, p->size,
> - &p->data);
> -
> - } else
> + if (p->dir)
> + r = kvm_io_bus_read(&vcpu->kvm->mmio_bus, p->addr, p->size,
> + &p->data);
> + else
> + r = kvm_io_bus_write(&vcpu->kvm->mmio_bus, p->addr, p->size,
> + &p->data);
> + if (r)
> printk(KERN_ERR"kvm: No iodevice found! addr:%lx\n", p->addr);
> p->state = STATE_IORESP_READY;
>
> diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
> index c13bb92..d5881a4 100644
> --- a/arch/x86/kvm/i8254.c
> +++ b/arch/x86/kvm/i8254.c
> @@ -336,8 +336,14 @@ void kvm_pit_load_count(struct kvm *kvm, int channel, u32 val)
> mutex_unlock(&kvm->arch.vpit->pit_state.lock);
> }
>
> -static void pit_ioport_write(struct kvm_io_device *this,
> - gpa_t addr, int len, const void *data)
> +static inline int pit_in_range(gpa_t addr)
> +{
> + return ((addr >= KVM_PIT_BASE_ADDRESS) &&
> + (addr < KVM_PIT_BASE_ADDRESS + KVM_PIT_MEM_LENGTH));
> +}
> +
> +static int pit_ioport_write(struct kvm_io_device *this,
> + gpa_t addr, int len, const void *data)
> {
> struct kvm_pit *pit = (struct kvm_pit *)this->private;
> struct kvm_kpit_state *pit_state = &pit->pit_state;
> @@ -345,6 +351,8 @@ static void pit_ioport_write(struct kvm_io_device *this,
> int channel, access;
> struct kvm_kpit_channel_state *s;
> u32 val = *(u32 *) data;
> + if (!pit_in_range(addr))
> + return -EOPNOTSUPP;
>
> val &= 0xff;
> addr &= KVM_PIT_CHANNEL_MASK;
> @@ -407,16 +415,19 @@ static void pit_ioport_write(struct kvm_io_device *this,
> }
>
> mutex_unlock(&pit_state->lock);
> + return 0;
> }
>
> -static void pit_ioport_read(struct kvm_io_device *this,
> - gpa_t addr, int len, void *data)
> +static int pit_ioport_read(struct kvm_io_device *this,
> + gpa_t addr, int len, void *data)
> {
> struct kvm_pit *pit = (struct kvm_pit *)this->private;
> struct kvm_kpit_state *pit_state = &pit->pit_state;
> struct kvm *kvm = pit->kvm;
> int ret, count;
> struct kvm_kpit_channel_state *s;
> + if (!pit_in_range(addr))
> + return -EOPNOTSUPP;
>
> addr &= KVM_PIT_CHANNEL_MASK;
> s = &pit_state->channels[addr];
> @@ -471,37 +482,36 @@ static void pit_ioport_read(struct kvm_io_device *this,
> memcpy(data, (char *)&ret, len);
>
> mutex_unlock(&pit_state->lock);
> + return 0;
> }
>
> -static int pit_in_range(struct kvm_io_device *this, gpa_t addr,
> - int len, int is_write)
> -{
> - return ((addr >= KVM_PIT_BASE_ADDRESS) &&
> - (addr < KVM_PIT_BASE_ADDRESS + KVM_PIT_MEM_LENGTH));
> -}
> -
> -static void speaker_ioport_write(struct kvm_io_device *this,
> - gpa_t addr, int len, const void *data)
> +static int speaker_ioport_write(struct kvm_io_device *this,
> + gpa_t addr, int len, const void *data)
> {
> struct kvm_pit *pit = (struct kvm_pit *)this->private;
> struct kvm_kpit_state *pit_state = &pit->pit_state;
> struct kvm *kvm = pit->kvm;
> u32 val = *(u32 *) data;
> + if (addr != KVM_SPEAKER_BASE_ADDRESS)
> + return -EOPNOTSUPP;
>
> mutex_lock(&pit_state->lock);
> pit_state->speaker_data_on = (val >> 1) & 1;
> pit_set_gate(kvm, 2, val & 1);
> mutex_unlock(&pit_state->lock);
> + return 0;
> }
>
> -static void speaker_ioport_read(struct kvm_io_device *this,
> - gpa_t addr, int len, void *data)
> +static int speaker_ioport_read(struct kvm_io_device *this,
> + gpa_t addr, int len, void *data)
> {
> struct kvm_pit *pit = (struct kvm_pit *)this->private;
> struct kvm_kpit_state *pit_state = &pit->pit_state;
> struct kvm *kvm = pit->kvm;
> unsigned int refresh_clock;
> int ret;
> + if (addr != KVM_SPEAKER_BASE_ADDRESS)
> + return -EOPNOTSUPP;
>
> /* Refresh clock toggles at about 15us. We approximate as 2^14ns. */
> refresh_clock = ((unsigned int)ktime_to_ns(ktime_get()) >> 14) & 1;
> @@ -513,12 +523,7 @@ static void speaker_ioport_read(struct kvm_io_device *this,
> len = sizeof(ret);
> memcpy(data, (char *)&ret, len);
> mutex_unlock(&pit_state->lock);
> -}
> -
> -static int speaker_in_range(struct kvm_io_device *this, gpa_t addr,
> - int len, int is_write)
> -{
> - return (addr == KVM_SPEAKER_BASE_ADDRESS);
> + return 0;
> }
>
> void kvm_pit_reset(struct kvm_pit *pit)
> @@ -571,13 +576,11 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm)
> /* Initialize PIO device */
> pit->dev.read = pit_ioport_read;
> pit->dev.write = pit_ioport_write;
> - pit->dev.in_range = pit_in_range;
> pit->dev.private = pit;
> kvm_io_bus_register_dev(&kvm->pio_bus, &pit->dev);
>
> pit->speaker_dev.read = speaker_ioport_read;
> pit->speaker_dev.write = speaker_ioport_write;
> - pit->speaker_dev.in_range = speaker_in_range;
> pit->speaker_dev.private = pit;
> kvm_io_bus_register_dev(&kvm->pio_bus, &pit->speaker_dev);
>
> diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
> index 1ccb50c..dc2d3a3 100644
> --- a/arch/x86/kvm/i8259.c
> +++ b/arch/x86/kvm/i8259.c
> @@ -428,8 +428,7 @@ static u32 elcr_ioport_read(void *opaque, u32 addr1)
> return s->elcr;
> }
>
> -static int picdev_in_range(struct kvm_io_device *this, gpa_t addr,
> - int len, int is_write)
> +static int picdev_in_range(gpa_t addr)
> {
> switch (addr) {
> case 0x20:
> @@ -444,16 +443,18 @@ static int picdev_in_range(struct kvm_io_device *this, gpa_t addr,
> }
> }
>
> -static void picdev_write(struct kvm_io_device *this,
> - gpa_t addr, int len, const void *val)
> +static int picdev_write(struct kvm_io_device *this,
> + gpa_t addr, int len, const void *val)
> {
> struct kvm_pic *s = this->private;
> unsigned char data = *(unsigned char *)val;
> + if (!picdev_in_range(addr))
> + return -EOPNOTSUPP;
>
> if (len != 1) {
> if (printk_ratelimit())
> printk(KERN_ERR "PIC: non byte write\n");
> - return;
> + return 0;
> }
> pic_lock(s);
> switch (addr) {
> @@ -469,18 +470,21 @@ static void picdev_write(struct kvm_io_device *this,
> break;
> }
> pic_unlock(s);
> + return 0;
> }
>
> -static void picdev_read(struct kvm_io_device *this,
> - gpa_t addr, int len, void *val)
> +static int picdev_read(struct kvm_io_device *this,
> + gpa_t addr, int len, void *val)
> {
> struct kvm_pic *s = this->private;
> unsigned char data = 0;
> + if (!picdev_in_range(addr))
> + return -EOPNOTSUPP;
>
> if (len != 1) {
> if (printk_ratelimit())
> printk(KERN_ERR "PIC: non byte read\n");
> - return;
> + return 0;
> }
> pic_lock(s);
> switch (addr) {
> @@ -497,6 +501,7 @@ static void picdev_read(struct kvm_io_device *this,
> }
> *(unsigned char *)val = data;
> pic_unlock(s);
> + return 0;
> }
>
> /*
> @@ -536,7 +541,6 @@ struct kvm_pic *kvm_create_pic(struct kvm *kvm)
> */
> s->dev.read = picdev_read;
> s->dev.write = picdev_write;
> - s->dev.in_range = picdev_in_range;
> s->dev.private = s;
> kvm_io_bus_register_dev(&kvm->pio_bus, &s->dev);
> return s;
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index f0b67f2..62e7e05 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -584,18 +584,27 @@ static u32 __apic_read(struct kvm_lapic *apic, unsigned int offset)
> return val;
> }
>
> -static void apic_mmio_read(struct kvm_io_device *this,
> - gpa_t address, int len, void *data)
> +static int apic_mmio_in_range(struct kvm_lapic *apic, gpa_t addr)
> {
> - struct kvm_lapic *apic = (struct kvm_lapic *)this->private;
> + return apic_hw_enabled(apic) &&
> + addr >= apic->base_address &&
> + addr < apic->base_address + LAPIC_MMIO_LENGTH;
> +}
> +
> +static int apic_mmio_read(struct kvm_io_device *this,
> + gpa_t address, int len, void *data)
> +{
> + struct kvm_lapic *apic = this->private;
> unsigned int offset = address - apic->base_address;
> unsigned char alignment = offset & 0xf;
> u32 result;
> + if (!apic_mmio_in_range(apic, address))
> + return -EOPNOTSUPP;
>
> if ((alignment + len) > 4) {
> printk(KERN_ERR "KVM_APIC_READ: alignment error %lx %d",
> (unsigned long)address, len);
> - return;
> + return 0;
> }
> result = __apic_read(apic, offset & ~0xf);
>
> @@ -610,6 +619,7 @@ static void apic_mmio_read(struct kvm_io_device *this,
> "should be 1,2, or 4 instead\n", len);
> break;
> }
> + return 0;
> }
>
> static void update_divide_count(struct kvm_lapic *apic)
> @@ -665,13 +675,15 @@ static void apic_manage_nmi_watchdog(struct kvm_lapic *apic, u32 lvt0_val)
> apic->vcpu->kvm->arch.vapics_in_nmi_mode--;
> }
>
> -static void apic_mmio_write(struct kvm_io_device *this,
> - gpa_t address, int len, const void *data)
> +static int apic_mmio_write(struct kvm_io_device *this,
> + gpa_t address, int len, const void *data)
> {
> - struct kvm_lapic *apic = (struct kvm_lapic *)this->private;
> + struct kvm_lapic *apic = this->private;
> unsigned int offset = address - apic->base_address;
> unsigned char alignment = offset & 0xf;
> u32 val;
> + if (!apic_mmio_in_range(apic, address))
> + return -EOPNOTSUPP;
>
> /*
> * APIC register must be aligned on 128-bits boundary.
> @@ -682,7 +694,7 @@ static void apic_mmio_write(struct kvm_io_device *this,
> /* Don't shout loud, $infamous_os would cause only noise. */
> apic_debug("apic write: bad size=%d %lx\n",
> len, (long)address);
> - return;
> + return 0;
> }
>
> val = *(u32 *) data;
> @@ -765,7 +777,7 @@ static void apic_mmio_write(struct kvm_io_device *this,
> hrtimer_cancel(&apic->timer.dev);
> apic_set_reg(apic, APIC_TMICT, val);
> start_apic_timer(apic);
> - return;
> + return 0;
>
> case APIC_TDCR:
> if (val & 4)
> @@ -779,22 +791,7 @@ static void apic_mmio_write(struct kvm_io_device *this,
> offset);
> break;
> }
> -
> -}
> -
> -static int apic_mmio_range(struct kvm_io_device *this, gpa_t addr,
> - int len, int size)
> -{
> - struct kvm_lapic *apic = (struct kvm_lapic *)this->private;
> - int ret = 0;
> -
> -
> - if (apic_hw_enabled(apic) &&
> - (addr >= apic->base_address) &&
> - (addr < (apic->base_address + LAPIC_MMIO_LENGTH)))
> - ret = 1;
> -
> - return ret;
> + return 0;
> }
>
> void kvm_free_lapic(struct kvm_vcpu *vcpu)
> @@ -1032,7 +1029,6 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu)
> kvm_lapic_reset(vcpu);
> apic->dev.read = apic_mmio_read;
> apic->dev.write = apic_mmio_write;
> - apic->dev.in_range = apic_mmio_range;
> apic->dev.private = apic;
>
> return 0;
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 3944e91..b6465c4 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -2016,35 +2016,23 @@ static void kvm_init_msr_list(void)
> num_msrs_to_save = j;
> }
>
> -/*
> - * Only apic need an MMIO device hook, so shortcut now..
> - */
> -static struct kvm_io_device *vcpu_find_pervcpu_dev(struct kvm_vcpu *vcpu,
> - gpa_t addr, int len,
> - int is_write)
> +static int vcpu_mmio_write(struct kvm_vcpu *vcpu, gpa_t addr, int len,
> + const void *val)
> {
> - struct kvm_io_device *dev;
> + if (vcpu->arch.apic &&
> + !kvm_iodevice_write(&vcpu->arch.apic->dev, addr, len, val))
> + return 0;
>
> - if (vcpu->arch.apic) {
> - dev = &vcpu->arch.apic->dev;
> - if (dev->in_range(dev, addr, len, is_write))
> - return dev;
> - }
> - return NULL;
> + return kvm_io_bus_write(&vcpu->kvm->mmio_bus, addr, len, val);
> }
>
> -
> -static struct kvm_io_device *vcpu_find_mmio_dev(struct kvm_vcpu *vcpu,
> - gpa_t addr, int len,
> - int is_write)
> +static int vcpu_mmio_read(struct kvm_vcpu *vcpu, gpa_t addr, int len, void *val)
> {
> - struct kvm_io_device *dev;
> + if (vcpu->arch.apic &&
> + !kvm_iodevice_read(&vcpu->arch.apic->dev, addr, len, val))
> + return 0;
>
> - dev = vcpu_find_pervcpu_dev(vcpu, addr, len, is_write);
> - if (dev == NULL)
> - dev = kvm_io_bus_find_dev(&vcpu->kvm->mmio_bus, addr, len,
> - is_write);
> - return dev;
> + return kvm_io_bus_read(&vcpu->kvm->mmio_bus, addr, len, val);
> }
>
> static int kvm_read_guest_virt(gva_t addr, void *val, unsigned int bytes,
> @@ -2113,7 +2101,6 @@ static int emulator_read_emulated(unsigned long addr,
> unsigned int bytes,
> struct kvm_vcpu *vcpu)
> {
> - struct kvm_io_device *mmio_dev;
> gpa_t gpa;
>
> if (vcpu->mmio_read_completed) {
> @@ -2139,9 +2126,7 @@ mmio:
> * Is this MMIO handled locally?
> */
> mutex_lock(&vcpu->kvm->lock);
> - mmio_dev = vcpu_find_mmio_dev(vcpu, gpa, bytes, 0);
> - if (mmio_dev) {
> - kvm_iodevice_read(mmio_dev, gpa, bytes, val);
> + if (!vcpu_mmio_read(vcpu, gpa, bytes, val)) {
> mutex_unlock(&vcpu->kvm->lock);
> return X86EMUL_CONTINUE;
> }
> @@ -2172,7 +2157,6 @@ static int emulator_write_emulated_onepage(unsigned long addr,
> unsigned int bytes,
> struct kvm_vcpu *vcpu)
> {
> - struct kvm_io_device *mmio_dev;
> gpa_t gpa;
>
> gpa = vcpu->arch.mmu.gva_to_gpa(vcpu, addr);
> @@ -2194,9 +2178,7 @@ mmio:
> * Is this MMIO handled locally?
> */
> mutex_lock(&vcpu->kvm->lock);
> - mmio_dev = vcpu_find_mmio_dev(vcpu, gpa, bytes, 1);
> - if (mmio_dev) {
> - kvm_iodevice_write(mmio_dev, gpa, bytes, val);
> + if (!vcpu_mmio_write(vcpu, gpa, bytes, val)) {
> mutex_unlock(&vcpu->kvm->lock);
> return X86EMUL_CONTINUE;
> }
> @@ -2508,52 +2490,45 @@ int complete_pio(struct kvm_vcpu *vcpu)
> return 0;
> }
>
> -static void kernel_pio(struct kvm_io_device *pio_dev,
> - struct kvm_vcpu *vcpu,
> - void *pd)
> +static int kernel_pio(struct kvm_vcpu *vcpu, void *pd)
> {
> /* TODO: String I/O for in kernel device */
> + int r;
>
> mutex_lock(&vcpu->kvm->lock);
> if (vcpu->arch.pio.in)
> - kvm_iodevice_read(pio_dev, vcpu->arch.pio.port,
> - vcpu->arch.pio.size,
> - pd);
> + r = kvm_io_bus_read(&vcpu->kvm->pio_bus, vcpu->arch.pio.port,
> + vcpu->arch.pio.size, pd);
> else
> - kvm_iodevice_write(pio_dev, vcpu->arch.pio.port,
> - vcpu->arch.pio.size,
> - pd);
> + r = kvm_io_bus_write(&vcpu->kvm->pio_bus, vcpu->arch.pio.port,
> + vcpu->arch.pio.size, pd);
> mutex_unlock(&vcpu->kvm->lock);
> + return r;
> }
>
> -static void pio_string_write(struct kvm_io_device *pio_dev,
> - struct kvm_vcpu *vcpu)
> +static int pio_string_write(struct kvm_vcpu *vcpu)
> {
> struct kvm_pio_request *io = &vcpu->arch.pio;
> void *pd = vcpu->arch.pio_data;
> - int i;
> + int i, r = 0;
>
> mutex_lock(&vcpu->kvm->lock);
> for (i = 0; i < io->cur_count; i++) {
> - kvm_iodevice_write(pio_dev, io->port,
> - io->size,
> - pd);
> + if (kvm_io_bus_write(&vcpu->kvm->pio_bus, io->port,
> + io->size,
> + pd)) {
> + r = -EOPNOTSUPP;
> + break;
> + }
> pd += io->size;
> }
> mutex_unlock(&vcpu->kvm->lock);
> -}
> -
> -static struct kvm_io_device *vcpu_find_pio_dev(struct kvm_vcpu *vcpu,
> - gpa_t addr, int len,
> - int is_write)
> -{
> - return kvm_io_bus_find_dev(&vcpu->kvm->pio_bus, addr, len, is_write);
> + return r;
> }
>
> int kvm_emulate_pio(struct kvm_vcpu *vcpu, struct kvm_run *run, int in,
> int size, unsigned port)
> {
> - struct kvm_io_device *pio_dev;
> unsigned long val;
>
> vcpu->run->exit_reason = KVM_EXIT_IO;
> @@ -2577,9 +2552,7 @@ int kvm_emulate_pio(struct kvm_vcpu *vcpu, struct kvm_run *run, int in,
> val = kvm_register_read(vcpu, VCPU_REGS_RAX);
> memcpy(vcpu->arch.pio_data, &val, 4);
>
> - pio_dev = vcpu_find_pio_dev(vcpu, port, size, !in);
> - if (pio_dev) {
> - kernel_pio(pio_dev, vcpu, vcpu->arch.pio_data);
> + if (!kernel_pio(vcpu, vcpu->arch.pio_data)) {
> complete_pio(vcpu);
> return 1;
> }
> @@ -2593,7 +2566,6 @@ int kvm_emulate_pio_string(struct kvm_vcpu *vcpu, struct kvm_run *run, int in,
> {
> unsigned now, in_page;
> int ret = 0;
> - struct kvm_io_device *pio_dev;
>
> vcpu->run->exit_reason = KVM_EXIT_IO;
> vcpu->run->io.direction = in ? KVM_EXIT_IO_IN : KVM_EXIT_IO_OUT;
> @@ -2641,9 +2613,6 @@ int kvm_emulate_pio_string(struct kvm_vcpu *vcpu, struct kvm_run *run, int in,
>
> vcpu->arch.pio.guest_gva = address;
>
> - pio_dev = vcpu_find_pio_dev(vcpu, port,
> - vcpu->arch.pio.cur_count,
> - !vcpu->arch.pio.in);
> if (!vcpu->arch.pio.in) {
> /* string PIO write */
> ret = pio_copy_data(vcpu);
> @@ -2651,16 +2620,13 @@ int kvm_emulate_pio_string(struct kvm_vcpu *vcpu, struct kvm_run *run, int in,
> kvm_inject_gp(vcpu, 0);
> return 1;
> }
> - if (ret == 0 && pio_dev) {
> - pio_string_write(pio_dev, vcpu);
> + if (ret == 0 && !pio_string_write(vcpu)) {
> complete_pio(vcpu);
> if (vcpu->arch.pio.count == 0)
> ret = 1;
> }
> - } else if (pio_dev)
> - pr_unimpl(vcpu, "no string pio read support yet, "
> - "port %x size %d count %ld\n",
> - port, size, count);
> + }
> + /* no string PIO read support yet */
>
> return ret;
> }
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 894a56e..2b9069f 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -58,8 +58,10 @@ struct kvm_io_bus {
>
> void kvm_io_bus_init(struct kvm_io_bus *bus);
> void kvm_io_bus_destroy(struct kvm_io_bus *bus);
> -struct kvm_io_device *kvm_io_bus_find_dev(struct kvm_io_bus *bus,
> - gpa_t addr, int len, int is_write);
> +int kvm_io_bus_write(struct kvm_io_bus *bus, gpa_t addr, int len,
> + const void *val);
> +int kvm_io_bus_read(struct kvm_io_bus *bus, gpa_t addr, int len,
> + void *val);
> void kvm_io_bus_register_dev(struct kvm_io_bus *bus,
> struct kvm_io_device *dev);
>
> diff --git a/virt/kvm/coalesced_mmio.c b/virt/kvm/coalesced_mmio.c
> index 5ae620d..d57b5ad 100644
> --- a/virt/kvm/coalesced_mmio.c
> +++ b/virt/kvm/coalesced_mmio.c
> @@ -14,21 +14,14 @@
>
> #include "coalesced_mmio.h"
>
> -static int coalesced_mmio_in_range(struct kvm_io_device *this,
> - gpa_t addr, int len, int is_write)
> +static int coalesced_mmio_in_range(struct kvm_coalesced_mmio_dev *dev,
> + gpa_t addr, int len)
> {
> - struct kvm_coalesced_mmio_dev *dev =
> - (struct kvm_coalesced_mmio_dev*)this->private;
> struct kvm_coalesced_mmio_zone *zone;
> int next;
> int i;
>
> - if (!is_write)
> - return 0;
> -
> - /* kvm->lock is taken by the caller and must be not released before
> - * dev.read/write
> - */
> + /* kvm->lock is taken by the caller */
>
> /* Are we able to batch it ? */
>
> @@ -60,14 +53,15 @@ static int coalesced_mmio_in_range(struct kvm_io_device *this,
> return 0;
> }
>
> -static void coalesced_mmio_write(struct kvm_io_device *this,
> - gpa_t addr, int len, const void *val)
> +static int coalesced_mmio_write(struct kvm_io_device *this,
> + gpa_t addr, int len, const void *val)
> {
> - struct kvm_coalesced_mmio_dev *dev =
> - (struct kvm_coalesced_mmio_dev*)this->private;
> + struct kvm_coalesced_mmio_dev *dev = this->private;
> struct kvm_coalesced_mmio_ring *ring = dev->kvm->coalesced_mmio_ring;
> + if (!coalesced_mmio_in_range(dev, addr, len))
> + return -EOPNOTSUPP;
>
> - /* kvm->lock must be taken by caller before call to in_range()*/
> + /* kvm->lock must be taken by caller */
>
> /* copy data in first free entry of the ring */
>
> @@ -76,6 +70,7 @@ static void coalesced_mmio_write(struct kvm_io_device *this,
> memcpy(ring->coalesced_mmio[ring->last].data, val, len);
> smp_wmb();
> ring->last = (ring->last + 1) % KVM_COALESCED_MMIO_MAX;
> + return 0;
> }
>
> static void coalesced_mmio_destructor(struct kvm_io_device *this)
> @@ -91,7 +86,6 @@ int kvm_coalesced_mmio_init(struct kvm *kvm)
> if (!dev)
> return -ENOMEM;
> dev->dev.write = coalesced_mmio_write;
> - dev->dev.in_range = coalesced_mmio_in_range;
> dev->dev.destructor = coalesced_mmio_destructor;
> dev->dev.private = dev;
> dev->kvm = kvm;
> diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
> index c3b99de..172e044 100644
> --- a/virt/kvm/ioapic.c
> +++ b/virt/kvm/ioapic.c
> @@ -329,20 +329,19 @@ void kvm_ioapic_update_eoi(struct kvm *kvm, int vector, int trigger_mode)
> __kvm_ioapic_update_eoi(ioapic, i, trigger_mode);
> }
>
> -static int ioapic_in_range(struct kvm_io_device *this, gpa_t addr,
> - int len, int is_write)
> +static inline int ioapic_in_range(struct kvm_ioapic *ioapic, gpa_t addr)
> {
> - struct kvm_ioapic *ioapic = (struct kvm_ioapic *)this->private;
> -
> return ((addr >= ioapic->base_address &&
> (addr < ioapic->base_address + IOAPIC_MEM_LENGTH)));
> }
>
> -static void ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
> - void *val)
> +static int ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
> + void *val)
> {
> - struct kvm_ioapic *ioapic = (struct kvm_ioapic *)this->private;
> + struct kvm_ioapic *ioapic = this->private;
> u32 result;
> + if (!ioapic_in_range(ioapic, addr))
> + return -ENOTSUPP;
>
> ioapic_debug("addr %lx\n", (unsigned long)addr);
> ASSERT(!(addr & 0xf)); /* check alignment */
> @@ -373,13 +372,16 @@ static void ioapic_mmio_read(struct kvm_io_device *this, gpa_t addr, int len,
> default:
> printk(KERN_WARNING "ioapic: wrong length %d\n", len);
> }
> + return 0;
> }
>
> -static void ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
> - const void *val)
> +static int ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
> + const void *val)
> {
> struct kvm_ioapic *ioapic = (struct kvm_ioapic *)this->private;
> u32 data;
> + if (!ioapic_in_range(ioapic, addr))
> + return -ENOTSUPP;
>
> ioapic_debug("ioapic_mmio_write addr=%p len=%d val=%p\n",
> (void*)addr, len, val);
> @@ -388,7 +390,7 @@ static void ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
> data = *(u32 *) val;
> else {
> printk(KERN_WARNING "ioapic: Unsupported size %d\n", len);
> - return;
> + return 0;
> }
>
> addr &= 0xff;
> @@ -409,6 +411,7 @@ static void ioapic_mmio_write(struct kvm_io_device *this, gpa_t addr, int len,
> default:
> break;
> }
> + return 0;
> }
>
> void kvm_ioapic_reset(struct kvm_ioapic *ioapic)
> @@ -434,7 +437,6 @@ int kvm_ioapic_init(struct kvm *kvm)
> kvm_ioapic_reset(ioapic);
> ioapic->dev.read = ioapic_mmio_read;
> ioapic->dev.write = ioapic_mmio_write;
> - ioapic->dev.in_range = ioapic_in_range;
> ioapic->dev.private = ioapic;
> ioapic->kvm = kvm;
> kvm_io_bus_register_dev(&kvm->mmio_bus, &ioapic->dev);
> diff --git a/virt/kvm/iodev.h b/virt/kvm/iodev.h
> index 55e8846..f891501 100644
> --- a/virt/kvm/iodev.h
> +++ b/virt/kvm/iodev.h
> @@ -17,43 +17,37 @@
> #define __KVM_IODEV_H__
>
> #include <linux/kvm_types.h>
> +#include <asm/errno.h>
>
> +/**
> + * read and write handlers are called under kvm_lock.
> + * They return 0 if the transaction has been handled,
> + * or non-zero to have it passed to the next device.
> + **/
> struct kvm_io_device {
> - void (*read)(struct kvm_io_device *this,
> + int (*read)(struct kvm_io_device *this,
> gpa_t addr,
> int len,
> void *val);
> - void (*write)(struct kvm_io_device *this,
> + int (*write)(struct kvm_io_device *this,
> gpa_t addr,
> int len,
> const void *val);
> - int (*in_range)(struct kvm_io_device *this, gpa_t addr, int len,
> - int is_write);
> void (*destructor)(struct kvm_io_device *this);
>
> void *private;
> };
>
> -static inline void kvm_iodevice_read(struct kvm_io_device *dev,
> - gpa_t addr,
> - int len,
> - void *val)
> +static inline int kvm_iodevice_read(struct kvm_io_device *dev,
> + gpa_t addr, int len, void *val)
> {
> - dev->read(dev, addr, len, val);
> + return dev->read ? dev->read(dev, addr, len, val) : -EOPNOTSUPP;
> }
>
> -static inline void kvm_iodevice_write(struct kvm_io_device *dev,
> - gpa_t addr,
> - int len,
> - const void *val)
> +static inline int kvm_iodevice_write(struct kvm_io_device *dev,
> + gpa_t addr, int len, const void *val)
> {
> - dev->write(dev, addr, len, val);
> -}
> -
> -static inline int kvm_iodevice_inrange(struct kvm_io_device *dev,
> - gpa_t addr, int len, int is_write)
> -{
> - return dev->in_range(dev, addr, len, is_write);
> + return dev->write ? dev->write(dev, addr, len, val) : -EOPNOTSUPP;
> }
>
> static inline void kvm_iodevice_destructor(struct kvm_io_device *dev)
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 4d0dd39..ed9e420 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -2145,19 +2145,24 @@ void kvm_io_bus_destroy(struct kvm_io_bus *bus)
> }
> }
>
> -struct kvm_io_device *kvm_io_bus_find_dev(struct kvm_io_bus *bus,
> - gpa_t addr, int len, int is_write)
> +int kvm_io_bus_write(struct kvm_io_bus *bus, gpa_t addr, int len,
> + const void *val)
> {
> int i;
> + for (i = 0; i < bus->dev_count; i++)
> + if (!kvm_iodevice_write(bus->devs[i], addr, len, val))
> + return 0;
> + return -ENOTSUPP;
> +}
>
> - for (i = 0; i < bus->dev_count; i++) {
> - struct kvm_io_device *pos = bus->devs[i];
> -
> - if (pos->in_range(pos, addr, len, is_write))
> - return pos;
> - }
> -
> - return NULL;
> +int kvm_io_bus_read(struct kvm_io_bus *bus, gpa_t addr, int len,
> + void *val)
> +{
> + int i;
> + for (i = 0; i < bus->dev_count; i++)
> + if (!kvm_iodevice_read(bus->devs[i], addr, len, val))
> + return 0;
> + return -ENOTSUPP;
> }
>
> void kvm_io_bus_register_dev(struct kvm_io_bus *bus, struct kvm_io_device *dev)