Subject: [PATCH v4 2/8] arm/arm64: KVM: vgic: switch to dynamic allocation

From: [email-masked] (Christoffer Dall)
Date: Thu, 11 Sep 2014 15:36:29 -0700

On Thu, Sep 11, 2014 at 12:09:09PM +0100, Marc Zyngier wrote:
> So far, all the VGIC data structures are statically defined by the
> *maximum* number of vcpus and interrupts it supports. It means that
> we always have to oversize it to cater for the worse case.
> 
> Start by changing the data structures to be dynamically sizeable,
> and allocate them at runtime.
> 
> The sizes are still very static though.
> 
> Signed-off-by: Marc Zyngier <[email-masked]>
> ---
>  arch/arm/kvm/arm.c     |   3 +
>  include/kvm/arm_vgic.h |  76 ++++++++++++----
>  virt/kvm/arm/vgic.c    | 237 ++++++++++++++++++++++++++++++++++++++++++-------
>  3 files changed, 267 insertions(+), 49 deletions(-)
> 
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index a99e0cd..923a01d 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -172,6 +172,8 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
>  			kvm->vcpus[i] = NULL;
>  		}
>  	}
> +
> +	kvm_vgic_destroy(kvm);
>  }
>  
>  int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> @@ -253,6 +255,7 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
>  {
>  	kvm_mmu_free_memory_caches(vcpu);
>  	kvm_timer_vcpu_terminate(vcpu);
> +	kvm_vgic_vcpu_destroy(vcpu);
>  	kmem_cache_free(kvm_vcpu_cache, vcpu);
>  }
>  
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index f074539..bdaac57 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -54,19 +54,33 @@
>   * - a bunch of shared interrupts (SPI)
>   */
>  struct vgic_bitmap {
> -	union {
> -		u32 reg[VGIC_NR_PRIVATE_IRQS / 32];
> -		DECLARE_BITMAP(reg_ul, VGIC_NR_PRIVATE_IRQS);
> -	} percpu[VGIC_MAX_CPUS];
> -	union {
> -		u32 reg[VGIC_NR_SHARED_IRQS / 32];
> -		DECLARE_BITMAP(reg_ul, VGIC_NR_SHARED_IRQS);
> -	} shared;
> +	/*
> +	 * - One UL per VCPU for private interrupts (assumes UL is at
> +	 *   least 32 bits)
> +	 * - As many UL as necessary for shared interrupts.
> +	 *
> +	 * The private interrupts are accessed via the "private"
> +	 * field, one UL per vcpu (the state for vcpu n is in
> +	 * private[n]). The shared interrupts are accessed via the
> +	 * "shared" pointer (IRQn state is at bit n-32 in the bitmap).
> +	 */
> +	unsigned long *private;
> +	unsigned long *shared;

the comment above the define for REG_OFFSET_SWIZZLE still talks about
the unions in struct vgic_bitmap, which is no longer true.  Mind
updating that comment?

>  };
>  
>  struct vgic_bytemap {
> -	u32 percpu[VGIC_MAX_CPUS][VGIC_NR_PRIVATE_IRQS / 4];
> -	u32 shared[VGIC_NR_SHARED_IRQS  / 4];
> +	/*
> +	 * - 8 u32 per VCPU for private interrupts
> +	 * - As many u32 as necessary for shared interrupts.
> +	 *
> +	 * The private interrupts are accessed via the "private"
> +	 * field, (the state for vcpu n is in private[n*8] to
> +	 * private[n*8 + 7]). The shared interrupts are accessed via
> +	 * the "shared" pointer (IRQn state is at byte (n-32)%4 of the
> +	 * shared[(n-32)/4] word).
> +	 */
> +	u32 *private;
> +	u32 *shared;
>  };
>  
>  struct kvm_vcpu;
> @@ -127,6 +141,9 @@ struct vgic_dist {
>  	bool			in_kernel;
>  	bool			ready;
>  
> +	int			nr_cpus;
> +	int			nr_irqs;
> +
>  	/* Virtual control interface mapping */
>  	void __iomem		*vctrl_base;
>  
> @@ -166,15 +183,36 @@ struct vgic_dist {
>  	/* Level/edge triggered */
>  	struct vgic_bitmap	irq_cfg;
>  
> -	/* Source CPU per SGI and target CPU */
> -	u8			irq_sgi_sources[VGIC_MAX_CPUS][VGIC_NR_SGIS];
> +	/*
> +	 * Source CPU per SGI and target CPU:
> +	 *
> +	 * Each byte represent a SGI observable on a VCPU, each bit of
> +	 * this byte indicating if the corresponding VCPU has
> +	 * generated this interrupt. This is a GICv2 feature only.
> +	 *
> +	 * For VCPUn (n < 8), irq_sgi_sources[n*16] to [n*16 + 15] are
> +	 * the SGIs observable on VCPUn.
> +	 */
> +	u8			*irq_sgi_sources;
>  
> -	/* Target CPU for each IRQ */
> -	u8			irq_spi_cpu[VGIC_NR_SHARED_IRQS];
> -	struct vgic_bitmap	irq_spi_target[VGIC_MAX_CPUS];
> +	/*
> +	 * Target CPU for each SPI:
> +	 *
> +	 * Array of available SPI, each byte indicating the target
> +	 * VCPU for SPI. IRQn (n >=32) is at irq_spi_cpu[n-32].
> +	 */
> +	u8			*irq_spi_cpu;
> +
> +	/*
> +	 * Reverse lookup of irq_spi_cpu for faster compute pending:
> +	 *
> +	 * Array of bitmaps, one per VCPU, describing is IRQn is

ah, describing *if* ?

> +	 * routed to a particular VCPU.
> +	 */
> +	struct vgic_bitmap	*irq_spi_target;
>  
>  	/* Bitmap indicating which CPU has something pending */
> -	unsigned long		irq_pending_on_cpu;
> +	unsigned long		*irq_pending_on_cpu;
>  #endif
>  };
>  
> @@ -204,11 +242,11 @@ struct vgic_v3_cpu_if {
>  struct vgic_cpu {
>  #ifdef CONFIG_KVM_ARM_VGIC
>  	/* per IRQ to LR mapping */
> -	u8		vgic_irq_lr_map[VGIC_NR_IRQS];
> +	u8		*vgic_irq_lr_map;
>  
>  	/* Pending interrupts on this VCPU */
>  	DECLARE_BITMAP(	pending_percpu, VGIC_NR_PRIVATE_IRQS);
> -	DECLARE_BITMAP(	pending_shared, VGIC_NR_SHARED_IRQS);
> +	unsigned long	*pending_shared;
>  
>  	/* Bitmap of used/free list registers */
>  	DECLARE_BITMAP(	lr_used, VGIC_V2_MAX_LRS);
> @@ -239,7 +277,9 @@ int kvm_vgic_addr(struct kvm *kvm, unsigned long type, u64 *addr, bool write);
>  int kvm_vgic_hyp_init(void);
>  int kvm_vgic_init(struct kvm *kvm);
>  int kvm_vgic_create(struct kvm *kvm);
> +void kvm_vgic_destroy(struct kvm *kvm);
>  int kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu);
> +void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu);
>  void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu);
>  void kvm_vgic_sync_hwstate(struct kvm_vcpu *vcpu);
>  int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int irq_num,
> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
> index d3299d4..92c086e 100644
> --- a/virt/kvm/arm/vgic.c
> +++ b/virt/kvm/arm/vgic.c
> @@ -95,6 +95,7 @@ static void vgic_retire_disabled_irqs(struct kvm_vcpu *vcpu);
>  static void vgic_retire_lr(int lr_nr, int irq, struct kvm_vcpu *vcpu);
>  static void vgic_update_state(struct kvm *kvm);
>  static void vgic_kick_vcpus(struct kvm *kvm);
> +static u8 *vgic_get_sgi_sources(struct vgic_dist *dist, int vcpu_id, int sgi);
>  static void vgic_dispatch_sgi(struct kvm_vcpu *vcpu, u32 reg);
>  static struct vgic_lr vgic_get_lr(const struct kvm_vcpu *vcpu, int lr);
>  static void vgic_set_lr(struct kvm_vcpu *vcpu, int lr, struct vgic_lr lr_desc);
> @@ -124,23 +125,45 @@ static const struct vgic_params *vgic;
>  #define REG_OFFSET_SWIZZLE	0
>  #endif
>  
> +static int vgic_init_bitmap(struct vgic_bitmap *b, int nr_cpus, int nr_irqs)
> +{
> +	int nr_longs;
> +
> +	nr_longs = nr_cpus + BITS_TO_LONGS(nr_irqs - VGIC_NR_PRIVATE_IRQS);
> +
> +	b->private = kzalloc(sizeof(unsigned long) * nr_longs, GFP_KERNEL);
> +	if (!b->private)
> +		return -ENOMEM;
> +
> +	b->shared = b->private + nr_cpus;
> +
> +	return 0;
> +}
> +
> +static void vgic_free_bitmap(struct vgic_bitmap *b)
> +{
> +	kfree(b->private);
> +	b->private = NULL;
> +	b->shared = NULL;
> +}
> +
>  static u32 *vgic_bitmap_get_reg(struct vgic_bitmap *x,
>  				int cpuid, u32 offset)
>  {
>  	offset >>= 2;
>  	if (!offset)
> -		return x->percpu[cpuid].reg + (offset ^ REG_OFFSET_SWIZZLE);
> +		return (u32 *)(x->private + cpuid) + REG_OFFSET_SWIZZLE;
>  	else
> -		return x->shared.reg + ((offset - 1) ^ REG_OFFSET_SWIZZLE);
> +		return (u32 *)(x->shared) + ((offset - 1) ^ REG_OFFSET_SWIZZLE);
>  }
>  
>  static int vgic_bitmap_get_irq_val(struct vgic_bitmap *x,
>  				   int cpuid, int irq)
>  {
>  	if (irq < VGIC_NR_PRIVATE_IRQS)
> -		return test_bit(irq, x->percpu[cpuid].reg_ul);
> +		return test_bit(irq, x->private + cpuid);
>  
> -	return test_bit(irq - VGIC_NR_PRIVATE_IRQS, x->shared.reg_ul);
> +	return test_bit(irq - VGIC_NR_PRIVATE_IRQS, x->shared);
>  }
>  
>  static void vgic_bitmap_set_irq_val(struct vgic_bitmap *x, int cpuid,
> @@ -149,9 +172,9 @@ static void vgic_bitmap_set_irq_val(struct vgic_bitmap *x, int cpuid,
>  	unsigned long *reg;
>  
>  	if (irq < VGIC_NR_PRIVATE_IRQS) {
> -		reg = x->percpu[cpuid].reg_ul;
> +		reg = x->private + cpuid;
>  	} else {
> -		reg =  x->shared.reg_ul;
> +		reg = x->shared;
>  		irq -= VGIC_NR_PRIVATE_IRQS;
>  	}
>  
> @@ -163,24 +186,49 @@ static void vgic_bitmap_set_irq_val(struct vgic_bitmap *x, int cpuid,
>  
>  static unsigned long *vgic_bitmap_get_cpu_map(struct vgic_bitmap *x, int cpuid)
>  {
> -	if (unlikely(cpuid >= VGIC_MAX_CPUS))
> -		return NULL;
> -	return x->percpu[cpuid].reg_ul;
> +	return x->private + cpuid;
>  }
>  
>  static unsigned long *vgic_bitmap_get_shared_map(struct vgic_bitmap *x)
>  {
> -	return x->shared.reg_ul;
> +	return x->shared;
> +}
> +
> +static int vgic_init_bytemap(struct vgic_bytemap *x, int nr_cpus, int nr_irqs)
> +{
> +	int size;
> +
> +	size  = nr_cpus * VGIC_NR_PRIVATE_IRQS;
> +	size += nr_irqs - VGIC_NR_PRIVATE_IRQS;
> +
> +	x->private = kzalloc(size, GFP_KERNEL);
> +	if (!x->private)
> +		return -ENOMEM;
> +
> +	x->shared = x->private + nr_cpus * VGIC_NR_PRIVATE_IRQS / sizeof(u32);
> +	return 0;
> +}
> +
> +static void vgic_free_bytemap(struct vgic_bytemap *b)
> +{
> +	kfree(b->private);
> +	b->private = NULL;
> +	b->shared = NULL;
>  }
>  
>  static u32 *vgic_bytemap_get_reg(struct vgic_bytemap *x, int cpuid, u32 offset)
>  {
> -	offset >>= 2;
> -	BUG_ON(offset > (VGIC_NR_IRQS / 4));
> -	if (offset < 8)
> -		return x->percpu[cpuid] + offset;
> -	else
> -		return x->shared + offset - 8;
> +	u32 *reg;
> +
> +	if (offset < VGIC_NR_PRIVATE_IRQS) {
> +		reg = x->private;
> +		offset += cpuid * VGIC_NR_PRIVATE_IRQS;
> +	} else {
> +		reg = x->shared;
> +		offset -= VGIC_NR_PRIVATE_IRQS;
> +	}
> +
> +	return reg + (offset / sizeof(u32));
>  }
>  
>  #define VGIC_CFG_LEVEL	0
> @@ -739,7 +787,7 @@ static void vgic_unqueue_irqs(struct kvm_vcpu *vcpu)
>  		 */
>  		vgic_dist_irq_set_pending(vcpu, lr.irq);
>  		if (lr.irq < VGIC_NR_SGIS)
> -			dist->irq_sgi_sources[vcpu_id][lr.irq] |= 1 << lr.source;
> +			*vgic_get_sgi_sources(dist, vcpu_id, lr.irq) |= 1 << lr.source;
>  		lr.state &= ~LR_STATE_PENDING;
>  		vgic_set_lr(vcpu, i, lr);
>  
> @@ -773,7 +821,7 @@ static bool read_set_clear_sgi_pend_reg(struct kvm_vcpu *vcpu,
>  	/* Copy source SGIs from distributor side */
>  	for (sgi = min_sgi; sgi <= max_sgi; sgi++) {
>  		int shift = 8 * (sgi - min_sgi);
> -		reg |= (u32)dist->irq_sgi_sources[vcpu_id][sgi] << shift;
> +		reg |= ((u32)*vgic_get_sgi_sources(dist, vcpu_id, sgi)) << shift;
>  	}
>  
>  	mmio_data_write(mmio, ~0, reg);
> @@ -797,14 +845,15 @@ static bool write_set_clear_sgi_pend_reg(struct kvm_vcpu *vcpu,
>  	/* Clear pending SGIs on the distributor */
>  	for (sgi = min_sgi; sgi <= max_sgi; sgi++) {
>  		u8 mask = reg >> (8 * (sgi - min_sgi));
> +		u8 *src = vgic_get_sgi_sources(dist, vcpu_id, sgi);
>  		if (set) {
> -			if ((dist->irq_sgi_sources[vcpu_id][sgi] & mask) != mask)
> +			if ((*src & mask) != mask)
>  				updated = true;
> -			dist->irq_sgi_sources[vcpu_id][sgi] |= mask;
> +			*src |= mask;
>  		} else {
> -			if (dist->irq_sgi_sources[vcpu_id][sgi] & mask)
> +			if (*src & mask)
>  				updated = true;
> -			dist->irq_sgi_sources[vcpu_id][sgi] &= ~mask;
> +			*src &= ~mask;
>  		}
>  	}
>  
> @@ -988,6 +1037,11 @@ bool vgic_handle_mmio(struct kvm_vcpu *vcpu, struct kvm_run *run,
>  	return true;
>  }
>  
> +static u8 *vgic_get_sgi_sources(struct vgic_dist *dist, int vcpu_id, int sgi)
> +{
> +	return dist->irq_sgi_sources + vcpu_id * VGIC_NR_SGIS + sgi;
> +}
> +
>  static void vgic_dispatch_sgi(struct kvm_vcpu *vcpu, u32 reg)
>  {
>  	struct kvm *kvm = vcpu->kvm;
> @@ -1021,7 +1075,7 @@ static void vgic_dispatch_sgi(struct kvm_vcpu *vcpu, u32 reg)
>  		if (target_cpus & 1) {
>  			/* Flag the SGI as pending */
>  			vgic_dist_irq_set_pending(vcpu, sgi);
> -			dist->irq_sgi_sources[c][sgi] |= 1 << vcpu_id;
> +			*vgic_get_sgi_sources(dist, c, sgi) |= 1 << vcpu_id;
>  			kvm_debug("SGI%d from CPU%d to CPU%d\n", sgi, vcpu_id, c);
>  		}
>  
> @@ -1068,14 +1122,14 @@ static void vgic_update_state(struct kvm *kvm)
>  	int c;
>  
>  	if (!dist->enabled) {
> -		set_bit(0, &dist->irq_pending_on_cpu);
> +		set_bit(0, dist->irq_pending_on_cpu);
>  		return;
>  	}
>  
>  	kvm_for_each_vcpu(c, vcpu, kvm) {
>  		if (compute_pending_for_cpu(vcpu)) {
>  			pr_debug("CPU%d has pending interrupts\n", c);
> -			set_bit(c, &dist->irq_pending_on_cpu);
> +			set_bit(c, dist->irq_pending_on_cpu);
>  		}
>  	}
>  }
> @@ -1232,14 +1286,14 @@ static bool vgic_queue_sgi(struct kvm_vcpu *vcpu, int irq)
>  	int vcpu_id = vcpu->vcpu_id;
>  	int c;
>  
> -	sources = dist->irq_sgi_sources[vcpu_id][irq];
> +	sources = *vgic_get_sgi_sources(dist, vcpu_id, irq);
>  
>  	for_each_set_bit(c, &sources, VGIC_MAX_CPUS) {
>  		if (vgic_queue_irq(vcpu, c, irq))
>  			clear_bit(c, &sources);
>  	}
>  
> -	dist->irq_sgi_sources[vcpu_id][irq] = sources;
> +	*vgic_get_sgi_sources(dist, vcpu_id, irq) = sources;
>  
>  	/*
>  	 * If the sources bitmap has been cleared it means that we
> @@ -1327,7 +1381,7 @@ epilog:
>  		 * us. Claim we don't have anything pending. We'll
>  		 * adjust that if needed while exiting.
>  		 */
> -		clear_bit(vcpu_id, &dist->irq_pending_on_cpu);
> +		clear_bit(vcpu_id, dist->irq_pending_on_cpu);
>  	}
>  }
>  
> @@ -1429,7 +1483,7 @@ static void __kvm_vgic_sync_hwstate(struct kvm_vcpu *vcpu)
>  	/* Check if we still have something up our sleeve... */
>  	pending = find_first_zero_bit(elrsr_ptr, vgic->nr_lr);
>  	if (level_pending || pending < vgic->nr_lr)
> -		set_bit(vcpu->vcpu_id, &dist->irq_pending_on_cpu);
> +		set_bit(vcpu->vcpu_id, dist->irq_pending_on_cpu);
>  }
>  
>  void kvm_vgic_flush_hwstate(struct kvm_vcpu *vcpu)
> @@ -1463,7 +1517,7 @@ int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu)
>  	if (!irqchip_in_kernel(vcpu->kvm))
>  		return 0;
>  
> -	return test_bit(vcpu->vcpu_id, &dist->irq_pending_on_cpu);
> +	return test_bit(vcpu->vcpu_id, dist->irq_pending_on_cpu);
>  }
>  
>  static void vgic_kick_vcpus(struct kvm *kvm)
> @@ -1558,7 +1612,7 @@ static bool vgic_update_irq_pending(struct kvm *kvm, int cpuid,
>  
>  	if (level) {
>  		vgic_cpu_irq_set(vcpu, irq_num);
> -		set_bit(cpuid, &dist->irq_pending_on_cpu);
> +		set_bit(cpuid, dist->irq_pending_on_cpu);
>  	}
>  
>  out:
> @@ -1602,6 +1656,32 @@ static irqreturn_t vgic_maintenance_handler(int irq, void *data)
>  	return IRQ_HANDLED;
>  }
>  
> +void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu)
> +{
> +	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
> +
> +	kfree(vgic_cpu->pending_shared);
> +	kfree(vgic_cpu->vgic_irq_lr_map);
> +	vgic_cpu->pending_shared = NULL;
> +	vgic_cpu->vgic_irq_lr_map = NULL;
> +}
> +
> +static int vgic_vcpu_init_maps(struct kvm_vcpu *vcpu, int nr_irqs)
> +{
> +	struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
> +
> +	int sz = (nr_irqs - VGIC_NR_PRIVATE_IRQS) / 8;

[copying question from last review round, apologies if I'm being stupid]

are we guaranteed that the numerator is always a multiple of 8? if not,
won't you end up allocating one less byte than needed?

> +	vgic_cpu->pending_shared = kzalloc(sz, GFP_KERNEL);
> +	vgic_cpu->vgic_irq_lr_map = kzalloc(nr_irqs, GFP_KERNEL);
> +
> +	if (!vgic_cpu->pending_shared || !vgic_cpu->vgic_irq_lr_map) {
> +		kvm_vgic_vcpu_destroy(vcpu);
> +		return -ENOMEM;
> +	}
> +
> +	return 0;
> +}
> +
[...]

Thanks,
-Christoffer