Subject: Re: [PATCH v2 04/16] KVM: PPC: Book3S HV: XIVE: add a control to initialize a source

From: David Gibson <[email-masked]>
Date: Mon, 25 Feb 2019 13:10:12 +1100

On Fri, Feb 22, 2019 at 12:28:28PM +0100, Cédric Le Goater wrote:
> The associated HW interrupt source is simply allocated at the OPAL/HW
> level and then MASKED. KVM only needs to know about its type: LSI or
> MSI.
> 
> Signed-off-by: Cédric Le Goater <[email-masked]>
> ---
>  arch/powerpc/include/uapi/asm/kvm.h        |   5 +
>  arch/powerpc/kvm/book3s_xive.h             |  10 ++
>  arch/powerpc/kvm/book3s_xive.c             |   8 +-
>  arch/powerpc/kvm/book3s_xive_native.c      | 114 +++++++++++++++++++++
>  Documentation/virtual/kvm/devices/xive.txt |  15 +++
>  5 files changed, 148 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
> index b002c0c67787..a9ad99f2a11b 100644
> --- a/arch/powerpc/include/uapi/asm/kvm.h
> +++ b/arch/powerpc/include/uapi/asm/kvm.h
> @@ -677,5 +677,10 @@ struct kvm_ppc_cpu_char {
>  
>  /* POWER9 XIVE Native Interrupt Controller */
>  #define KVM_DEV_XIVE_GRP_CTRL		1
> +#define KVM_DEV_XIVE_GRP_SOURCE		2	/* 64-bit source attributes */
> +
> +/* Layout of 64-bit XIVE source attribute values */
> +#define KVM_XIVE_LEVEL_SENSITIVE	(1ULL << 0)
> +#define KVM_XIVE_LEVEL_ASSERTED		(1ULL << 1)
>  
>  #endif /* __LINUX_KVM_POWERPC_H */
> diff --git a/arch/powerpc/kvm/book3s_xive.h b/arch/powerpc/kvm/book3s_xive.h
> index bcb1bbcf0359..f22f2d46d0f0 100644
> --- a/arch/powerpc/kvm/book3s_xive.h
> +++ b/arch/powerpc/kvm/book3s_xive.h
> @@ -12,6 +12,13 @@
>  #ifdef CONFIG_KVM_XICS
>  #include "book3s_xics.h"
>  
> +/*
> + * The XIVE IRQ number space is aligned with the XICS IRQ number
> + * space, CPU IPIs being allocated in the first 4K.

We do align these in qemu, but I don't see that the kernel part
cares: as far as it's concerned only one of XICS or XIVE is active at
a time, and the irq numbers are chosen by userspace.

> + */
> +#define KVMPPC_XIVE_FIRST_IRQ	0
> +#define KVMPPC_XIVE_NR_IRQS	KVMPPC_XICS_NR_IRQS
> +
>  /*
>   * State for one guest irq source.
>   *
> @@ -253,6 +260,9 @@ extern int (*__xive_vm_h_eoi)(struct kvm_vcpu *vcpu, unsigned long xirr);
>   */
>  void kvmppc_xive_disable_vcpu_interrupts(struct kvm_vcpu *vcpu);
>  int kvmppc_xive_debug_show_queues(struct seq_file *m, struct kvm_vcpu *vcpu);
> +struct kvmppc_xive_src_block *kvmppc_xive_create_src_block(
> +	struct kvmppc_xive *xive, int irq);
> +void kvmppc_xive_free_sources(struct kvmppc_xive_src_block *sb);
>  
>  #endif /* CONFIG_KVM_XICS */
>  #endif /* _KVM_PPC_BOOK3S_XICS_H */
> diff --git a/arch/powerpc/kvm/book3s_xive.c b/arch/powerpc/kvm/book3s_xive.c
> index d1cc18a5b1c4..6f950ecb3592 100644
> --- a/arch/powerpc/kvm/book3s_xive.c
> +++ b/arch/powerpc/kvm/book3s_xive.c

I wonder if we should rename this book3s_xics_on_xive.c or something
at some point, I keep getting confused because I forget that this is
only dealing with host xive, not guest xive.

> @@ -1485,8 +1485,8 @@ static int xive_get_source(struct kvmppc_xive *xive, long irq, u64 addr)
>  	return 0;
>  }
>  
> -static struct kvmppc_xive_src_block *xive_create_src_block(struct kvmppc_xive *xive,
> -							   int irq)
> +struct kvmppc_xive_src_block *kvmppc_xive_create_src_block(
> +	struct kvmppc_xive *xive, int irq)
>  {
>  	struct kvm *kvm = xive->kvm;
>  	struct kvmppc_xive_src_block *sb;

It's odd that this function, now used from the xive-on-xive path as
well as the xics-on-xive path references KVMPPC_XICS_ICS_SHIFT a few
lines down from this change.

> @@ -1565,7 +1565,7 @@ static int xive_set_source(struct kvmppc_xive *xive, long irq, u64 addr)
>  	sb = kvmppc_xive_find_source(xive, irq, &idx);
>  	if (!sb) {
>  		pr_devel("No source, creating source block...\n");
> -		sb = xive_create_src_block(xive, irq);
> +		sb = kvmppc_xive_create_src_block(xive, irq);
>  		if (!sb) {
>  			pr_devel("Failed to create block...\n");
>  			return -ENOMEM;
> @@ -1789,7 +1789,7 @@ static void kvmppc_xive_cleanup_irq(u32 hw_num, struct xive_irq_data *xd)
>  	xive_cleanup_irq_data(xd);
>  }
>  
> -static void kvmppc_xive_free_sources(struct kvmppc_xive_src_block *sb)
> +void kvmppc_xive_free_sources(struct kvmppc_xive_src_block *sb)
>  {
>  	int i;
>  
> diff --git a/arch/powerpc/kvm/book3s_xive_native.c b/arch/powerpc/kvm/book3s_xive_native.c
> index 1f3da47a4a6a..a9b2d2d9af99 100644
> --- a/arch/powerpc/kvm/book3s_xive_native.c
> +++ b/arch/powerpc/kvm/book3s_xive_native.c
> @@ -31,6 +31,29 @@
>  
>  #include "book3s_xive.h"
>  
> +/*
> + * TODO: introduce a common template file with the XIVE native layer
> + * and the XICS-on-XIVE glue for the utility functions
> + */
> +#define __x_eoi_page(xd)	((void __iomem *)((xd)->eoi_mmio))
> +#define __x_trig_page(xd)	((void __iomem *)((xd)->trig_mmio))
> +#define __x_readq	__raw_readq
> +#define __x_writeq	__raw_writeq
> +
> +static u8 xive_vm_esb_load(struct xive_irq_data *xd, u32 offset)
> +{
> +	u64 val;
> +
> +	if (xd->flags & XIVE_IRQ_FLAG_SHIFT_BUG)
> +		offset |= offset << 4;
> +
> +	val = __x_readq(__x_eoi_page(xd) + offset);
> +#ifdef __LITTLE_ENDIAN__
> +	val >>= 64-8;
> +#endif
> +	return (u8)val;
> +}
> +
>  static void kvmppc_xive_native_cleanup_queue(struct kvm_vcpu *vcpu, int prio)
>  {
>  	struct kvmppc_xive_vcpu *xc = vcpu->arch.xive_vcpu;
> @@ -153,12 +176,89 @@ int kvmppc_xive_native_connect_vcpu(struct kvm_device *dev,
>  	return rc;
>  }
>  
> +static int kvmppc_xive_native_set_source(struct kvmppc_xive *xive, long irq,
> +					 u64 addr)
> +{
> +	struct kvmppc_xive_src_block *sb;
> +	struct kvmppc_xive_irq_state *state;
> +	u64 __user *ubufp = (u64 __user *) addr;
> +	u64 val;
> +	u16 idx;
> +
> +	pr_devel("%s irq=0x%lx\n", __func__, irq);
> +
> +	if (irq < KVMPPC_XIVE_FIRST_IRQ || irq >= KVMPPC_XIVE_NR_IRQS)
> +		return -E2BIG;
> +
> +	sb = kvmppc_xive_find_source(xive, irq, &idx);
> +	if (!sb) {
> +		pr_debug("No source, creating source block...\n");
> +		sb = kvmppc_xive_create_src_block(xive, irq);
> +		if (!sb) {
> +			pr_err("Failed to create block...\n");
> +			return -ENOMEM;
> +		}
> +	}
> +	state = &sb->irq_state[idx];
> +
> +	if (get_user(val, ubufp)) {
> +		pr_err("fault getting user info !\n");
> +		return -EFAULT;
> +	}

You should validate the value loaded here to check it doesn't have any
bits set we don't know about.

> +
> +	/*
> +	 * If the source doesn't already have an IPI, allocate
> +	 * one and get the corresponding data
> +	 */
> +	if (!state->ipi_number) {
> +		state->ipi_number = xive_native_alloc_irq();
> +		if (state->ipi_number == 0) {
> +			pr_err("Failed to allocate IRQ !\n");
> +			return -ENXIO;
> +		}
> +		xive_native_populate_irq_data(state->ipi_number,
> +					      &state->ipi_data);
> +		pr_debug("%s allocated hw_irq=0x%x for irq=0x%lx\n", __func__,
> +			 state->ipi_number, irq);
> +	}
> +
> +	arch_spin_lock(&sb->lock);

Why the direct call to arch_spin_lock() rather than just spin_lock()?

> +
> +	/* Restore LSI state */
> +	if (val & KVM_XIVE_LEVEL_SENSITIVE) {
> +		state->lsi = true;
> +		if (val & KVM_XIVE_LEVEL_ASSERTED)
> +			state->asserted = true;
> +		pr_devel("  LSI ! Asserted=%d\n", state->asserted);
> +	}
> +
> +	/* Mask IRQ to start with */
> +	state->act_server = 0;
> +	state->act_priority = MASKED;
> +	xive_vm_esb_load(&state->ipi_data, XIVE_ESB_SET_PQ_01);
> +	xive_native_configure_irq(state->ipi_number, 0, MASKED, 0);
> +
> +	/* Increment the number of valid sources and mark this one valid */
> +	if (!state->valid)
> +		xive->src_count++;
> +	state->valid = true;
> +
> +	arch_spin_unlock(&sb->lock);
> +
> +	return 0;
> +}
> +
>  static int kvmppc_xive_native_set_attr(struct kvm_device *dev,
>  				       struct kvm_device_attr *attr)
>  {
> +	struct kvmppc_xive *xive = dev->private;
> +
>  	switch (attr->group) {
>  	case KVM_DEV_XIVE_GRP_CTRL:
>  		break;
> +	case KVM_DEV_XIVE_GRP_SOURCE:
> +		return kvmppc_xive_native_set_source(xive, attr->attr,
> +						     attr->addr);
>  	}
>  	return -ENXIO;
>  }
> @@ -175,6 +275,11 @@ static int kvmppc_xive_native_has_attr(struct kvm_device *dev,
>  	switch (attr->group) {
>  	case KVM_DEV_XIVE_GRP_CTRL:
>  		break;
> +	case KVM_DEV_XIVE_GRP_SOURCE:
> +		if (attr->attr >= KVMPPC_XIVE_FIRST_IRQ &&
> +		    attr->attr < KVMPPC_XIVE_NR_IRQS)
> +			return 0;
> +		break;
>  	}
>  	return -ENXIO;
>  }
> @@ -183,6 +288,7 @@ static void kvmppc_xive_native_free(struct kvm_device *dev)
>  {
>  	struct kvmppc_xive *xive = dev->private;
>  	struct kvm *kvm = xive->kvm;
> +	int i;
>  
>  	debugfs_remove(xive->dentry);
>  
> @@ -191,6 +297,14 @@ static void kvmppc_xive_native_free(struct kvm_device *dev)
>  	if (kvm)
>  		kvm->arch.xive = NULL;
>  
> +	/* Mask and free interrupts */
> +	for (i = 0; i <= xive->max_sbid; i++) {
> +		if (xive->src_blocks[i])
> +			kvmppc_xive_free_sources(xive->src_blocks[i]);
> +		kfree(xive->src_blocks[i]);
> +		xive->src_blocks[i] = NULL;
> +	}
> +
>  	if (xive->vp_base != XIVE_INVALID_VP)
>  		xive_native_free_vp_block(xive->vp_base);
>  
> diff --git a/Documentation/virtual/kvm/devices/xive.txt b/Documentation/virtual/kvm/devices/xive.txt
> index fdbd2ff92a88..cd8bfc37b72e 100644
> --- a/Documentation/virtual/kvm/devices/xive.txt
> +++ b/Documentation/virtual/kvm/devices/xive.txt
> @@ -17,3 +17,18 @@ the legacy interrupt mode, referred as XICS (POWER7/8).
>  
>    1. KVM_DEV_XIVE_GRP_CTRL
>    Provides global controls on the device
> +
> +  2. KVM_DEV_XIVE_GRP_SOURCE (write only)
> +  Initializes a new source in the XIVE device and mask it.
> +  Attributes:
> +    Interrupt source number  (64-bit)
> +  The kvm_device_attr.addr points to a __u64 value:
> +  bits:     | 63   ....  2 |   1   |   0
> +  values:   |    unused    | level | type
> +  - type:  0:MSI 1:LSI
> +  - level: assertion level in case of an LSI.
> +  Errors:
> +    -E2BIG:  Interrupt source number is out of range
> +    -ENOMEM: Could not create a new source block
> +    -EFAULT: Invalid user pointer for attr->addr.
> +    -ENXIO:  Could not allocate underlying HW interrupt

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson