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

Christoffer Dall
2014-09-11T22:36:31Z

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 <marc.zyngier@arm.com>
> ---
> 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