Subject: [PATCH v4 17/19] arm64: KVM: add SGI generation register emulation

From: [email-masked] (Christoffer Dall)
Date: Sun, 23 Nov 2014 16:08:52 +0100

On Fri, Nov 14, 2014 at 10:08:01AM +0000, Andre Przywara wrote:
> While the generation of a (virtual) inter-processor interrupt (SGI)
> on a GICv2 works by writing to a MMIO register, GICv3 uses the system
> register ICC_SGI1R_EL1 to trigger them.
> Trap that register on ARM64 hosts and handle it in a new handler
> function in the GICv3 emulation code.

Did you reorder something or does my previous comment still apply that
you're not enabling trapping yet, you're just adding the handler - those
are two different things.

You sort of left my question about access_gic_sgi() not checking if the
gicv3 is presetn hanging from the last thread, but I think I'm
understanding properly now, that as long as you're not setting the
ICC_SRE_EL2.Enable = 1, then we'll never get here, right?

> 
> Signed-off-by: Andre Przywara <[email-masked]>
> ---
> Changelog v3...v4:
> - moved addition of vgic_v3_dispatch_sgi() from earlier patch into here
> - move MPIDR comparison into extra function
> - use new ICC_SGI1R_ field names
> - improve readability of vgic_v3_dispatch_sgi()
> - add and refine comments
> 
>  arch/arm64/kvm/sys_regs.c   |   26 ++++++++++
>  include/kvm/arm_vgic.h      |    1 +
>  virt/kvm/arm/vgic-v3-emul.c |  113 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 140 insertions(+)
> 
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index fd3ffc3..e59369a 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -165,6 +165,27 @@ static bool access_sctlr(struct kvm_vcpu *vcpu,
>  	return true;
>  }
>  
> +/*
> + * Trap handler for the GICv3 SGI generation system register.
> + * Forward the request to the VGIC emulation.
> + * The cp15_64 code makes sure this automatically works
> + * for both AArch64 and AArch32 accesses.
> + */
> +static bool access_gic_sgi(struct kvm_vcpu *vcpu,
> +			   const struct sys_reg_params *p,
> +			   const struct sys_reg_desc *r)
> +{
> +	u64 val;
> +
> +	if (!p->is_write)
> +		return read_from_write_only(vcpu, p);
> +
> +	val = *vcpu_reg(vcpu, p->Rt);
> +	vgic_v3_dispatch_sgi(vcpu, val);
> +
> +	return true;
> +}
> +
>  static bool trap_raz_wi(struct kvm_vcpu *vcpu,
>  			const struct sys_reg_params *p,
>  			const struct sys_reg_desc *r)
> @@ -431,6 +452,9 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>  	/* VBAR_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b1100), CRm(0b0000), Op2(0b000),
>  	  NULL, reset_val, VBAR_EL1, 0 },
> +	/* ICC_SGI1R_EL1 */
> +	{ Op0(0b11), Op1(0b000), CRn(0b1100), CRm(0b1011), Op2(0b101),
> +	  access_gic_sgi },
>  	/* CONTEXTIDR_EL1 */
>  	{ Op0(0b11), Op1(0b000), CRn(0b1101), CRm(0b0000), Op2(0b001),
>  	  access_vm_reg, reset_val, CONTEXTIDR_EL1, 0 },
> @@ -659,6 +683,8 @@ static const struct sys_reg_desc cp14_64_regs[] = {
>   * register).
>   */
>  static const struct sys_reg_desc cp15_regs[] = {
> +	{ Op1( 0), CRn( 0), CRm(12), Op2( 0), access_gic_sgi },
> +
>  	{ Op1( 0), CRn( 1), CRm( 0), Op2( 0), access_sctlr, NULL, c1_SCTLR },
>  	{ Op1( 0), CRn( 2), CRm( 0), Op2( 0), access_vm_reg, NULL, c2_TTBR0 },
>  	{ Op1( 0), CRn( 2), CRm( 0), Op2( 1), access_vm_reg, NULL, c2_TTBR1 },
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index c1ef5a9..357a935 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -305,6 +305,7 @@ 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,
>  			bool level);
> +void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg);
>  int kvm_vgic_vcpu_pending_irq(struct kvm_vcpu *vcpu);
>  bool vgic_handle_mmio(struct kvm_vcpu *vcpu, struct kvm_run *run,
>  		      struct kvm_exit_mmio *mmio);
> diff --git a/virt/kvm/arm/vgic-v3-emul.c b/virt/kvm/arm/vgic-v3-emul.c
> index 97b5801..58d7457 100644
> --- a/virt/kvm/arm/vgic-v3-emul.c
> +++ b/virt/kvm/arm/vgic-v3-emul.c
> @@ -828,6 +828,119 @@ int vgic_v3_init_emulation(struct kvm *kvm)
>  	return 0;
>  }
>  
> +/*
> + * Compare a given affinity (level 1-3 and a level 0 mask, from the SGI
> + * generation register ICC_SGI1R_EL1) with a given VCPU.
> + * If the VCPU's MPIDR matches, return the level0 affinity, otherwise
> + * return -1.
> + */
> +static int match_mpidr(u64 sgi_aff, u16 sgi_cpu_mask, struct kvm_vcpu *vcpu)
> +{
> +	unsigned long affinity;
> +	int level0;
> +
> +	/*
> +	 * Split the current VCPU's MPIDR into affinity level 0 and the
> +	 * rest as this is what we have to compare against.
> +	 */
> +	affinity = kvm_vcpu_get_mpidr_aff(vcpu);
> +	level0 = MPIDR_AFFINITY_LEVEL(affinity, 0);
> +	affinity &= ~MPIDR_LEVEL_MASK;
> +
> +	/* bail out if the upper three levels don't match */
> +	if (sgi_aff != affinity)
> +		return -1;
> +
> +	/* Is this VCPU's bit set in the mask ? */
> +	if (!(sgi_cpu_mask & BIT(level0)))
> +		return -1;
> +
> +	return level0;
> +}
> +
> +#define SGI_AFFINITY_LEVEL(reg, level) \
> +	((((reg) & ICC_SGI1R_AFFINITY_## level ##_MASK) \
> +	>> ICC_SGI1R_AFFINITY_## level ##_SHIFT) << MPIDR_LEVEL_SHIFT(level))
> +
> +/**
> + * vgic_v3_dispatch_sgi - handle SGI requests from VCPUs
> + * @vcpu: The VCPU requesting a SGI
> + * @reg: The value written into the ICC_SGI1R_EL1 register by that VCPU
> + *
> + * With GICv3 (and ARE=1) CPUs trigger SGIs by writing to an architectural

what's a non-architectural system register?

> + * system register. This will trap in sys_regs.c and call this function.
> + * This ICC_SGI1R_EL1 register contains the upper three affinity levels of the
> + * target processors as well as a bitmask of 16 Aff0 CPUs.
> + * If the interrupt routing mode bit is not set, we iterate over all VCPUs to
> + * check for matching ones. If this bit is set, we signal all, but not the
> + * calling VCPU.
> + */
> +void vgic_v3_dispatch_sgi(struct kvm_vcpu *vcpu, u64 reg)
> +{
> +	struct kvm *kvm = vcpu->kvm;
> +	struct kvm_vcpu *c_vcpu;
> +	struct vgic_dist *dist = &kvm->arch.vgic;
> +	u16 target_cpus;
> +	u64 mpidr;
> +	int sgi, c, vcpu_id;
> +	bool broadcast;
> +	int updated = 0;
> +
> +	vcpu_id = vcpu->vcpu_id;
> +
> +	sgi = (reg & ICC_SGI1R_SGI_ID_MASK) >> ICC_SGI1R_SGI_ID_SHIFT;
> +	broadcast = reg & BIT(ICC_SGI1R_IRQ_ROUTING_MODE_BIT);
> +	target_cpus = (reg & ICC_SGI1R_TARGET_LIST_MASK) >> ICC_SGI1R_TARGET_LIST_SHIFT;
> +	mpidr = SGI_AFFINITY_LEVEL(reg, 3);
> +	mpidr |= SGI_AFFINITY_LEVEL(reg, 2);
> +	mpidr |= SGI_AFFINITY_LEVEL(reg, 1);
> +	mpidr &= ~MPIDR_LEVEL_MASK;

do you need this last mask?  It should be 0 already, right?

> +
> +	/*
> +	 * We take the dist lock here, because we come from the sysregs
> +	 * code path and not from the MMIO one (which already takes the lock).
> +	 */
> +	spin_lock(&dist->lock);
> +
> +	/*
> +	 * We iterate over all VCPUs to find the MPIDRs matching the request.
> +	 * If we have handled one CPU, we clear it's bit to detect early
> +	 * if we are already finished. This avoids iterating through all
> +	 * VCPUs when most of the times we just signal a single VCPU.
> +	 */
> +	kvm_for_each_vcpu(c, c_vcpu, kvm) {
> +
> +		/* Exit early if we have dealt with all requested CPUs */
> +		if (!broadcast && target_cpus == 0)
> +			break;
> +
> +		 /* Don't signal the calling VCPU */
> +		if (broadcast && c == vcpu_id)
> +			continue;
> +
> +		if (!broadcast) {
> +			int level0;
> +
> +			level0 = match_mpidr(mpidr, target_cpus, c_vcpu);
> +			if (level0 == -1)
> +				continue;
> +
> +			/* remove this matching VCPU from the mask */
> +			target_cpus &= ~BIT(level0);
> +		}
> +
> +		/* Flag the SGI as pending */
> +		vgic_dist_irq_set_pending(c_vcpu, sgi);
> +		updated = 1;
> +		kvm_debug("SGI%d from CPU%d to CPU%d\n", sgi, vcpu_id, c);
> +	}
> +	if (updated)
> +		vgic_update_state(vcpu->kvm);
> +	spin_unlock(&dist->lock);
> +	if (updated)
> +		vgic_kick_vcpus(vcpu->kvm);
> +}
> +
>  static int vgic_v3_create(struct kvm_device *dev, u32 type)
>  {
>  	return kvm_vgic_create(dev->kvm, type);
> -- 
> 1.7.9.5
> 

Assuming you'll address the commit message stuff above:

Reviewed-by: Christoffer Dall <[email-masked]>