Subject: [RFC PATCH v3 1/5] arm/arm64: vgic-new: Implement support for userspace access

From: [email-masked] (Christoffer Dall)
Date: Tue, 30 Aug 2016 12:31:50 +0200

On Wed, Aug 24, 2016 at 04:50:05PM +0530, vijay.kilari at gmail.com wrote:
> From: Vijaya Kumar K <[email-masked]>
> 
> Read and write of some registers like ISPENDR and ICPENDR
> from userspace requires special handling when compared to
> guest access for these registers.
> 
> Refer to Documentation/virtual/kvm/devices/arm-vgic-its.txt

you mean arm-vgic-v3.txt right?

> for handling of ISPENDR, ICPENDR registers handling.
> 
> Add infrastructure to support guest and userspace read
> and write for the required registers
> 
> Signed-off-by: Vijaya Kumar K <[email-masked]>
> ---
>  virt/kvm/arm/vgic/vgic-mmio-v2.c |  5 ++-
>  virt/kvm/arm/vgic/vgic-mmio-v3.c | 40 ++++++++++++++----
>  virt/kvm/arm/vgic/vgic-mmio.c    | 87 ++++++++++++++++++++++++++++++++++++----
>  virt/kvm/arm/vgic/vgic-mmio.h    | 25 ++++++++++++
>  4 files changed, 139 insertions(+), 18 deletions(-)
> 
> diff --git a/virt/kvm/arm/vgic/vgic-mmio-v2.c b/virt/kvm/arm/vgic/vgic-mmio-v2.c
> index b44b359..cd37159 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio-v2.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio-v2.c
> @@ -421,9 +421,10 @@ static int vgic_uaccess(struct kvm_vcpu *vcpu, struct vgic_io_device *dev,
>  
>  	if (is_write) {
>  		vgic_data_host_to_mmio_bus(buf, len, *val);
> -		ret = kvm_io_gic_ops.write(vcpu, &dev->dev, offset, len, buf);
> +		ret = vgic_mmio_uaccess_write(vcpu, &dev->dev, offset,
> +					      len, buf);
>  	} else {
> -		ret = kvm_io_gic_ops.read(vcpu, &dev->dev, offset, len, buf);
> +		ret = vgic_mmio_uaccess_read(vcpu, &dev->dev, offset, len, buf);
>  		if (!ret)
>  			*val = vgic_data_mmio_bus_to_host(buf, len);
>  	}
> diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c
> index ff668e0..dd0d602 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio-v3.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c
> @@ -367,6 +367,26 @@ static void vgic_mmio_write_pendbase(struct kvm_vcpu *vcpu,
>  		.write = wr,						\
>  	}
>  
> +#define REGISTER_DESC_WITH_BITS_PER_IRQ_SHARED_UACCESS(off, rd, wr, ur, \
> +							uw, bpi, acc)	\
> +	{								\
> +		.reg_offset = off,					\
> +		.bits_per_irq = bpi,					\
> +		.len = (bpi * VGIC_NR_PRIVATE_IRQS) / 8,		\
> +		.access_flags = acc,					\
> +		.read = vgic_mmio_read_raz,				\
> +		.write = vgic_mmio_write_wi,				\
> +	}, {								\
> +		.reg_offset = off + (bpi * VGIC_NR_PRIVATE_IRQS) / 8,	\
> +		.bits_per_irq = bpi,					\
> +		.len = (bpi * (1024 - VGIC_NR_PRIVATE_IRQS)) / 8,	\
> +		.access_flags = acc,					\
> +		.read = rd,						\
> +		.write = wr,						\
> +		.uaccess_read = ur,					\
> +		.uaccess_write = uw,					\
> +	}
> +

that macro name is getting really long and complicated.

Could we consider simply modifying the existing macro to take two
additional parameters, and change the list of users of the macro to pass
NULL where these functions are not used?

>  static const struct vgic_register_region vgic_v3_dist_registers[] = {
>  	REGISTER_DESC_WITH_LENGTH(GICD_CTLR,
>  		vgic_mmio_read_v3_misc, vgic_mmio_write_v3_misc, 16,
> @@ -380,11 +400,13 @@ static const struct vgic_register_region vgic_v3_dist_registers[] = {
>  	REGISTER_DESC_WITH_BITS_PER_IRQ_SHARED(GICD_ICENABLER,
>  		vgic_mmio_read_enable, vgic_mmio_write_cenable, 1,
>  		VGIC_ACCESS_32bit),
> -	REGISTER_DESC_WITH_BITS_PER_IRQ_SHARED(GICD_ISPENDR,
> -		vgic_mmio_read_pending, vgic_mmio_write_spending, 1,
> +	REGISTER_DESC_WITH_BITS_PER_IRQ_SHARED_UACCESS(GICD_ISPENDR,
> +		vgic_mmio_read_pending, vgic_mmio_write_spending,
> +		vgic_mmio_read_soft_pending, vgic_mmio_write_spending, 1,

You need a uaccess for the write part as well to provide raw access to
the latch state, without imposing any ordering requirements for the
restore part of userspace.  For example, you cannot rely on userspace
having restored the configuration state of the IRQs before the pending
state, unless we modify the API to require this.

I think you need a function that looks very similar tot he
write_spending function, but which always sets the soft_pending state,
regardless of the configuration of the IRQ.

We need to tweak the vgic_mmio_write_config function to queue interrupts
that become pending when changed to LEVEL to go along with this.  I can
send a patch with this separately.

>  		VGIC_ACCESS_32bit),
> -	REGISTER_DESC_WITH_BITS_PER_IRQ_SHARED(GICD_ICPENDR,
> -		vgic_mmio_read_pending, vgic_mmio_write_cpending, 1,
> +	REGISTER_DESC_WITH_BITS_PER_IRQ_SHARED_UACCESS(GICD_ICPENDR,
> +		vgic_mmio_read_pending, vgic_mmio_write_cpending,
> +		vgic_mmio_read_soft_pending, vgic_mmio_write_cpending, 1,
>  		VGIC_ACCESS_32bit),
>  	REGISTER_DESC_WITH_BITS_PER_IRQ_SHARED(GICD_ISACTIVER,
>  		vgic_mmio_read_active, vgic_mmio_write_sactive, 1,
> @@ -443,11 +465,13 @@ static const struct vgic_register_region vgic_v3_sgibase_registers[] = {
>  	REGISTER_DESC_WITH_LENGTH(GICR_ICENABLER0,
>  		vgic_mmio_read_enable, vgic_mmio_write_cenable, 4,
>  		VGIC_ACCESS_32bit),
> -	REGISTER_DESC_WITH_LENGTH(GICR_ISPENDR0,
> -		vgic_mmio_read_pending, vgic_mmio_write_spending, 4,
> +	REGISTER_DESC_WITH_LENGTH_UACCESS(GICR_ISPENDR0,
> +		vgic_mmio_read_pending, vgic_mmio_write_spending,
> +		vgic_mmio_read_soft_pending, vgic_mmio_write_spending, 4,
>  		VGIC_ACCESS_32bit),
> -	REGISTER_DESC_WITH_LENGTH(GICR_ICPENDR0,
> -		vgic_mmio_read_pending, vgic_mmio_write_cpending, 4,
> +	REGISTER_DESC_WITH_LENGTH_UACCESS(GICR_ICPENDR0,
> +		vgic_mmio_read_pending, vgic_mmio_write_cpending,
> +		vgic_mmio_read_soft_pending, vgic_mmio_write_cpending, 4,
>  		VGIC_ACCESS_32bit),
>  	REGISTER_DESC_WITH_LENGTH(GICR_ISACTIVER0,
>  		vgic_mmio_read_active, vgic_mmio_write_sactive, 4,
> diff --git a/virt/kvm/arm/vgic/vgic-mmio.c b/virt/kvm/arm/vgic/vgic-mmio.c
> index 3bad3c5..dcf5d25 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio.c
> +++ b/virt/kvm/arm/vgic/vgic-mmio.c
> @@ -100,6 +100,26 @@ void vgic_mmio_write_cenable(struct kvm_vcpu *vcpu,
>  	}
>  }
>  
> +unsigned long vgic_mmio_read_soft_pending(struct kvm_vcpu *vcpu,
> +					  gpa_t addr, unsigned int len)

since this is only reading the soft_pending state for level triggered
interrupts, I don't appreciate this name.

How about vgic_uaccess_read_pending ?

> +{
> +	u32 intid = VGIC_ADDR_TO_INTID(addr, 1);
> +	u32 value = 0;
> +	int i;
> +
> +	/* Loop over all IRQs affected by this read */
> +	for (i = 0; i < len * 8; i++) {
> +		struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, intid + i);
> +

Add a comment with a reference to the logic defined in the
arm-vgic-v3.txt for this implementation here.

> +		if (irq->config == VGIC_CONFIG_LEVEL && irq->soft_pending)
> +			value |= (1U << i);
> +		if (irq->config != VGIC_CONFIG_LEVEL && irq->pending)

please change the latter to irq->config == VGIC_CONFIG_EDGE.

> +			value |= (1U << i);
> +	}
> +
> +	return value;
> +}
> +
>  unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
>  				     gpa_t addr, unsigned int len)
>  {
> @@ -468,6 +488,62 @@ static bool check_region(const struct vgic_register_region *region,
>  	return false;
>  }
>  
> +static const struct vgic_register_region *
> +	vgic_get_mmio_region(struct vgic_io_device *iodev, gpa_t addr, int len)
> +{
> +	const struct vgic_register_region *region;
> +
> +	region = vgic_find_mmio_region(iodev->regions, iodev->nr_regions,
> +				       addr - iodev->base_addr);
> +	if (!region || !check_region(region, addr, len))
> +		return NULL;
> +
> +	return region;
> +}
> +
> +int vgic_mmio_uaccess_read(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
> +			   gpa_t addr, int len, void *val)

I would probably rename these two functions to be
vgic_uaccess_read/write, that is get rid of the 'mmio' part.

> +{
> +	struct vgic_io_device *iodev = kvm_to_vgic_iodev(dev);
> +	const struct vgic_register_region *region;
> +	struct kvm_vcpu *r_vcpu;
> +	unsigned long data;
> +
> +	region = vgic_get_mmio_region(iodev, addr, len);
> +	if (!region) {
> +		memset(val, 0, len);
> +		return 0;
> +	}
> +
> +	r_vcpu = iodev->redist_vcpu ? iodev->redist_vcpu : vcpu;
> +	if (region->uaccess_read != NULL)
> +		data = region->uaccess_read(r_vcpu, addr, len);
> +	else
> +		data = region->read(r_vcpu, addr, len);
> +	vgic_data_host_to_mmio_bus(val, len, data);
> +	return 0;
> +}
> +
> +int vgic_mmio_uaccess_write(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
> +			    gpa_t addr, int len, const void *val)
> +{
> +	struct vgic_io_device *iodev = kvm_to_vgic_iodev(dev);
> +	const struct vgic_register_region *region;
> +	struct kvm_vcpu *r_vcpu;
> +	unsigned long data = vgic_data_mmio_bus_to_host(val, len);
> +
> +	region = vgic_get_mmio_region(iodev, addr, len);
> +	if (!region)
> +		return 0;
> +
> +	r_vcpu = iodev->redist_vcpu ? iodev->redist_vcpu : vcpu;
> +	if (region->uaccess_write != NULL)
> +		region->uaccess_write(r_vcpu, addr, len, data);
> +	else
> +		region->write(r_vcpu, addr, len, data);
> +	return 0;
> +}
> +
>  static int dispatch_mmio_read(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
>  			      gpa_t addr, int len, void *val)
>  {
> @@ -475,9 +551,8 @@ static int dispatch_mmio_read(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
>  	const struct vgic_register_region *region;
>  	unsigned long data = 0;
>  
> -	region = vgic_find_mmio_region(iodev->regions, iodev->nr_regions,
> -				       addr - iodev->base_addr);
> -	if (!region || !check_region(region, addr, len)) {
> +	region = vgic_get_mmio_region(iodev, addr, len);
> +	if (!region) {
>  		memset(val, 0, len);
>  		return 0;
>  	}
> @@ -508,14 +583,10 @@ static int dispatch_mmio_write(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
>  	const struct vgic_register_region *region;
>  	unsigned long data = vgic_data_mmio_bus_to_host(val, len);
>  
> -	region = vgic_find_mmio_region(iodev->regions, iodev->nr_regions,
> -				       addr - iodev->base_addr);
> +	region = vgic_get_mmio_region(iodev, addr, len);
>  	if (!region)
>  		return 0;
>  
> -	if (!check_region(region, addr, len))
> -		return 0;
> -
>  	switch (iodev->iodev_type) {
>  	case IODEV_CPUIF:
>  		region->write(vcpu, addr, len, data);
> diff --git a/virt/kvm/arm/vgic/vgic-mmio.h b/virt/kvm/arm/vgic/vgic-mmio.h
> index 0b3ecf9..b97a97b 100644
> --- a/virt/kvm/arm/vgic/vgic-mmio.h
> +++ b/virt/kvm/arm/vgic/vgic-mmio.h
> @@ -34,6 +34,10 @@ struct vgic_register_region {
>  				  gpa_t addr, unsigned int len,
>  				  unsigned long val);
>  	};
> +	unsigned long (*uaccess_read)(struct kvm_vcpu *vcpu, gpa_t addr,
> +				      unsigned int len);
> +	void (*uaccess_write)(struct kvm_vcpu *vcpu, gpa_t addr,
> +			      unsigned int len, unsigned long val);
>  };
>  
>  extern struct kvm_io_device_ops kvm_io_gic_ops;
> @@ -86,6 +90,18 @@ extern struct kvm_io_device_ops kvm_io_gic_ops;
>  		.write = wr,						\
>  	}
>  
> +#define REGISTER_DESC_WITH_LENGTH_UACCESS(off, rd, wr, urd, uwr, length, acc) \
> +	{								\
> +		.reg_offset = off,					\
> +		.bits_per_irq = 0,					\
> +		.len = length,						\
> +		.access_flags = acc,					\
> +		.read = rd,						\
> +		.write = wr,						\
> +		.uaccess_read = urd,					\
> +		.uaccess_write = uwr,					\
> +	}
> +
>  int kvm_vgic_register_mmio_region(struct kvm *kvm, struct kvm_vcpu *vcpu,
>  				  struct vgic_register_region *reg_desc,
>  				  struct vgic_io_device *region,
> @@ -122,6 +138,9 @@ void vgic_mmio_write_cenable(struct kvm_vcpu *vcpu,
>  			     gpa_t addr, unsigned int len,
>  			     unsigned long val);
>  
> +unsigned long vgic_mmio_read_soft_pending(struct kvm_vcpu *vcpu,
> +					  gpa_t addr, unsigned int len);
> +
>  unsigned long vgic_mmio_read_pending(struct kvm_vcpu *vcpu,
>  				     gpa_t addr, unsigned int len);
>  
> @@ -158,6 +177,12 @@ void vgic_mmio_write_config(struct kvm_vcpu *vcpu,
>  			    gpa_t addr, unsigned int len,
>  			    unsigned long val);
>  
> +int vgic_mmio_uaccess_read(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
> +			   gpa_t addr, int len, void *val);
> +
> +int vgic_mmio_uaccess_write(struct kvm_vcpu *vcpu, struct kvm_io_device *dev,
> +			    gpa_t addr, int len, const void *val);
> +
>  unsigned int vgic_v2_init_dist_iodev(struct vgic_io_device *dev);
>  
>  unsigned int vgic_v3_init_dist_iodev(struct vgic_io_device *dev);
> -- 
> 1.9.1
>