Re: [PATCH kvmtool v2 04/22] mmio: Extend handling to include ioport emulation

[Andre Przywara <andre.przywara@arm.com>]

On Wed, 3 Mar 2021 17:58:29 +0000
Alexandru Elisei <alexandru.elisei@arm.com> wrote:

Hi Alex,

> On 2/25/21 12:58 AM, Andre Przywara wrote:
> > In their core functionality MMIO and I/O port traps are not really
> > different, yet we still have two totally separate code paths for
> > handling them. Devices need to decide on one conduit or need to provide
> > different handler functions for each of them.
> >
> > Extend the existing MMIO emulation to also cover ioport handlers.
> > This just adds another RB tree root for holding the I/O port handlers,
> > but otherwise uses the same tree population and lookup code.
> > "ioport" or "mmio" just become a flag in the registration function.
> > Provide wrappers to not break existing users, and allow an easy
> > transition for the existing ioport handlers.
> >
> > This also means that ioport handlers now can use the same emulation
> > callback prototype as MMIO handlers, which means we have to migrate them
> > over. To allow a smooth transition, we hook up the new I/O emulate
> > function to the end of the existing ioport emulation code.
> >
> > Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> > ---
> >  include/kvm/kvm.h | 49 ++++++++++++++++++++++++++++++++---
> >  ioport.c          |  4 +--
> >  mmio.c            | 65 +++++++++++++++++++++++++++++++++++++++--------
> >  3 files changed, 102 insertions(+), 16 deletions(-)
> >
> > diff --git a/include/kvm/kvm.h b/include/kvm/kvm.h
> > index f1f0afd7..306b258a 100644
> > --- a/include/kvm/kvm.h
> > +++ b/include/kvm/kvm.h
> > @@ -27,10 +27,23 @@
> >  #define PAGE_SIZE (sysconf(_SC_PAGE_SIZE))
> >  #endif
> >  
> > +/*
> > + * We are reusing the existing DEVICE_BUS_MMIO and DEVICE_BUS_IOPORT constants
> > + * from kvm/devices.h to differentiate between registering an I/O port and an
> > + * MMIO region.
> > + * To avoid collisions with future additions of more bus types, we reserve
> > + * a generous 4 bits for the bus mask here.
> > + */
> > +#define IOTRAP_BUS_MASK		0xf
> > +#define IOTRAP_COALESCE		(1U << 4)
> > +
> >  #define DEFINE_KVM_EXT(ext)		\
> >  	.name = #ext,			\
> >  	.code = ext
> >  
> > +struct kvm_cpu;
> > +typedef void (*mmio_handler_fn)(struct kvm_cpu *vcpu, u64 addr, u8 *data,
> > +				u32 len, u8 is_write, void *ptr);
> >  typedef void (*fdt_irq_fn)(void *fdt, u8 irq, enum irq_type irq_type);
> >  
> >  enum {
> > @@ -113,6 +126,8 @@ void kvm__irq_line(struct kvm *kvm, int irq, int level);
> >  void kvm__irq_trigger(struct kvm *kvm, int irq);
> >  bool kvm__emulate_io(struct kvm_cpu *vcpu, u16 port, void *data, int direction, int size, u32 count);
> >  bool kvm__emulate_mmio(struct kvm_cpu *vcpu, u64 phys_addr, u8 *data, u32 len, u8 is_write);
> > +bool kvm__emulate_pio(struct kvm_cpu *vcpu, u16 port, void *data,
> > +		      int direction, int size, u32 count);
> >  int kvm__destroy_mem(struct kvm *kvm, u64 guest_phys, u64 size, void *userspace_addr);
> >  int kvm__register_mem(struct kvm *kvm, u64 guest_phys, u64 size, void *userspace_addr,
> >  		      enum kvm_mem_type type);
> > @@ -136,10 +151,36 @@ static inline int kvm__reserve_mem(struct kvm *kvm, u64 guest_phys, u64 size)
> >  				 KVM_MEM_TYPE_RESERVED);
> >  }
> >  
> > -int __must_check kvm__register_mmio(struct kvm *kvm, u64 phys_addr, u64 phys_addr_len, bool coalesce,
> > -				    void (*mmio_fn)(struct kvm_cpu *vcpu, u64 addr, u8 *data, u32 len, u8 is_write, void *ptr),
> > -				    void *ptr);
> > -bool kvm__deregister_mmio(struct kvm *kvm, u64 phys_addr);
> > +int __must_check kvm__register_iotrap(struct kvm *kvm, u64 phys_addr, u64 len,
> > +				      mmio_handler_fn mmio_fn, void *ptr,
> > +				      unsigned int flags);
> > +
> > +static inline
> > +int __must_check kvm__register_mmio(struct kvm *kvm, u64 phys_addr,
> > +				    u64 phys_addr_len, bool coalesce,
> > +				    mmio_handler_fn mmio_fn, void *ptr)
> > +{
> > +	return kvm__register_iotrap(kvm, phys_addr, phys_addr_len, mmio_fn, ptr,
> > +			DEVICE_BUS_MMIO | (coalesce ? IOTRAP_COALESCE : 0));
> > +}
> > +static inline
> > +int __must_check kvm__register_pio(struct kvm *kvm, u16 port, u16 len,
> > +				   mmio_handler_fn mmio_fn, void *ptr)
> > +{
> > +	return kvm__register_iotrap(kvm, port, len, mmio_fn, ptr,
> > +				    DEVICE_BUS_IOPORT);
> > +}
> > +
> > +bool kvm__deregister_iotrap(struct kvm *kvm, u64 phys_addr, unsigned int flags);
> > +static inline bool kvm__deregister_mmio(struct kvm *kvm, u64 phys_addr)
> > +{
> > +	return kvm__deregister_iotrap(kvm, phys_addr, DEVICE_BUS_MMIO);
> > +}
> > +static inline bool kvm__deregister_pio(struct kvm *kvm, u16 port)
> > +{
> > +	return kvm__deregister_iotrap(kvm, port, DEVICE_BUS_IOPORT);
> > +}
> > +
> >  void kvm__reboot(struct kvm *kvm);
> >  void kvm__pause(struct kvm *kvm);
> >  void kvm__continue(struct kvm *kvm);
> > diff --git a/ioport.c b/ioport.c
> > index e0123f27..ce29e7e7 100644
> > --- a/ioport.c
> > +++ b/ioport.c
> > @@ -162,7 +162,8 @@ bool kvm__emulate_io(struct kvm_cpu *vcpu, u16 port, void *data, int direction,
> >  
> >  	entry = ioport_get(&ioport_tree, port);
> >  	if (!entry)
> > -		goto out;
> > +		return kvm__emulate_pio(vcpu, port, data, direction,
> > +					size, count);
> >  
> >  	ops	= entry->ops;
> >  
> > @@ -177,7 +178,6 @@ bool kvm__emulate_io(struct kvm_cpu *vcpu, u16 port, void *data, int direction,
> >  
> >  	ioport_put(&ioport_tree, entry);
> >  
> > -out:
> >  	if (ret)
> >  		return true;
> >  
> > diff --git a/mmio.c b/mmio.c
> > index cd141cd3..75de04ad 100644
> > --- a/mmio.c
> > +++ b/mmio.c
> > @@ -19,13 +19,14 @@ static DEFINE_MUTEX(mmio_lock);
> >  
> >  struct mmio_mapping {
> >  	struct rb_int_node	node;
> > -	void			(*mmio_fn)(struct kvm_cpu *vcpu, u64 addr, u8 *data, u32 len, u8 is_write, void *ptr);
> > +	mmio_handler_fn		mmio_fn;
> >  	void			*ptr;
> >  	u32			refcount;
> >  	bool			remove;
> >  };
> >  
> >  static struct rb_root mmio_tree = RB_ROOT;
> > +static struct rb_root pio_tree = RB_ROOT;
> >  
> >  static struct mmio_mapping *mmio_search(struct rb_root *root, u64 addr, u64 len)
> >  {
> > @@ -103,9 +104,14 @@ static void mmio_put(struct kvm *kvm, struct rb_root *root, struct mmio_mapping
> >  	mutex_unlock(&mmio_lock);
> >  }
> >  
> > -int kvm__register_mmio(struct kvm *kvm, u64 phys_addr, u64 phys_addr_len, bool coalesce,
> > -		       void (*mmio_fn)(struct kvm_cpu *vcpu, u64 addr, u8 *data, u32 len, u8 is_write, void *ptr),
> > -			void *ptr)
> > +static bool trap_is_mmio(unsigned int flags)
> > +{
> > +	return (flags & IOTRAP_BUS_MASK) == DEVICE_BUS_MMIO;
> > +}
> > +
> > +int kvm__register_iotrap(struct kvm *kvm, u64 phys_addr, u64 phys_addr_len,
> > +			 mmio_handler_fn mmio_fn, void *ptr,
> > +			 unsigned int flags)
> >  {
> >  	struct mmio_mapping *mmio;
> >  	struct kvm_coalesced_mmio_zone zone;
> > @@ -127,7 +133,7 @@ int kvm__register_mmio(struct kvm *kvm, u64 phys_addr, u64 phys_addr_len, bool c
> >  		.remove		= false,
> >  	};
> >  
> > -	if (coalesce) {
> > +	if (trap_is_mmio(flags) && (flags & IOTRAP_COALESCE)) {
> >  		zone = (struct kvm_coalesced_mmio_zone) {
> >  			.addr	= phys_addr,
> >  			.size	= phys_addr_len,
> > @@ -138,19 +144,29 @@ int kvm__register_mmio(struct kvm *kvm, u64 phys_addr, u64 phys_addr_len, bool c
> >  			return -errno;
> >  		}
> >  	}
> > +
> >  	mutex_lock(&mmio_lock);
> > -	ret = mmio_insert(&mmio_tree, mmio);
> > +	if (trap_is_mmio(flags))
> > +		ret = mmio_insert(&mmio_tree, mmio);
> > +	else
> > +		ret = mmio_insert(&pio_tree, mmio);
> >  	mutex_unlock(&mmio_lock);
> >  
> >  	return ret;
> >  }
> >  
> > -bool kvm__deregister_mmio(struct kvm *kvm, u64 phys_addr)
> > +bool kvm__deregister_iotrap(struct kvm *kvm, u64 phys_addr, unsigned int flags)
> >  {
> >  	struct mmio_mapping *mmio;
> > +	struct rb_root *tree;
> > +
> > +	if ((flags & IOTRAP_BUS_MASK) == DEVICE_BUS_IOPORT)
> > +		tree = &pio_tree;
> > +	else
> > +		tree = &mmio_tree;  
> 
> We could swap the conditional branches and use trap_is_mmio(flags) like we do above.

Of course! Fixed that.

> Regardless, the patch looks really good:
> 
> Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>

Thanks!
Andre

> >  
> >  	mutex_lock(&mmio_lock);
> > -	mmio = mmio_search_single(&mmio_tree, phys_addr);
> > +	mmio = mmio_search_single(tree, phys_addr);
> >  	if (mmio == NULL) {
> >  		mutex_unlock(&mmio_lock);
> >  		return false;
> > @@ -167,7 +183,7 @@ bool kvm__deregister_mmio(struct kvm *kvm, u64 phys_addr)
> >  	 * called mmio_put(). This will trigger use-after-free errors on VCPU0.
> >  	 */
> >  	if (mmio->refcount == 0)
> > -		mmio_deregister(kvm, &mmio_tree, mmio);
> > +		mmio_deregister(kvm, tree, mmio);
> >  	else
> >  		mmio->remove = true;
> >  	mutex_unlock(&mmio_lock);
> > @@ -175,7 +191,8 @@ bool kvm__deregister_mmio(struct kvm *kvm, u64 phys_addr)
> >  	return true;
> >  }
> >  
> > -bool kvm__emulate_mmio(struct kvm_cpu *vcpu, u64 phys_addr, u8 *data, u32 len, u8 is_write)
> > +bool kvm__emulate_mmio(struct kvm_cpu *vcpu, u64 phys_addr, u8 *data,
> > +		       u32 len, u8 is_write)
> >  {
> >  	struct mmio_mapping *mmio;
> >  
> > @@ -194,3 +211,31 @@ bool kvm__emulate_mmio(struct kvm_cpu *vcpu, u64 phys_addr, u8 *data, u32 len, u
> >  out:
> >  	return true;
> >  }
> > +
> > +bool kvm__emulate_pio(struct kvm_cpu *vcpu, u16 port, void *data,
> > +		     int direction, int size, u32 count)
> > +{
> > +	struct mmio_mapping *mmio;
> > +	bool is_write = direction == KVM_EXIT_IO_OUT;
> > +
> > +	mmio = mmio_get(&pio_tree, port, size);
> > +	if (!mmio) {
> > +		if (vcpu->kvm->cfg.ioport_debug) {
> > +			fprintf(stderr, "IO error: %s port=%x, size=%d, count=%u\n",
> > +				to_direction(direction), port, size, count);
> > +
> > +			return false;
> > +		}
> > +		return true;
> > +	}
> > +
> > +	while (count--) {
> > +		mmio->mmio_fn(vcpu, port, data, size, is_write, mmio->ptr);
> > +
> > +		data += size;
> > +	}
> > +
> > +	mmio_put(vcpu->kvm, &pio_tree, mmio);
> > +
> > +	return true;
> > +}