Re: [PATCH v2] KVM: arm/arm64: vgic: Add debugfs vgic-state file

[Christoffer Dall <christoffer.dall@linaro.org>]

On Wed, Jan 25, 2017 at 10:07:15AM +0100, Auger Eric wrote:
> Hi Christoffer,
> 
> On 24/01/2017 14:25, Christoffer Dall wrote:
> > Add a file to debugfs to read the in-kernel state of the vgic.  We don't
> > do any locking of the entire VGIC state while traversing all the IRQs,
> > so if the VM is running the user/developer may not see a quiesced state,
> > but should take care to pause the VM using facilities in user space for
> > that purpose.
> > 
> > We also don't support LPIs yet, but they can be added easily if needed.
> > 
> > Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> > ---
> > Changes since v1:
> >  - Check error code in vgic_debug_stop so that users which did not
> >    succeed in opening the seq file also doesn't do the cleanup, which
> >    could lead to a kernel crash with multiple readers of this file
> >    before.
> >  - Renamed some functions to be a bit less cute
> >  - Rebased on the patch that gets rid of the pendin field in struct
> >    vgic_irq.
> > 
> >  arch/arm/kvm/Makefile          |   1 +
> >  arch/arm64/kvm/Makefile        |   1 +
> >  include/kvm/arm_vgic.h         |   5 +
> >  virt/kvm/arm/vgic/vgic-debug.c | 284 +++++++++++++++++++++++++++++++++++++++++
> >  virt/kvm/arm/vgic/vgic-init.c  |   4 +
> >  virt/kvm/arm/vgic/vgic.h       |   3 +
> >  6 files changed, 298 insertions(+)
> >  create mode 100644 virt/kvm/arm/vgic/vgic-debug.c
> > 
> > diff --git a/arch/arm/kvm/Makefile b/arch/arm/kvm/Makefile
> > index d571243..12b6281 100644
> > --- a/arch/arm/kvm/Makefile
> > +++ b/arch/arm/kvm/Makefile
> > @@ -33,5 +33,6 @@ obj-y += $(KVM)/arm/vgic/vgic-mmio-v2.o
> >  obj-y += $(KVM)/arm/vgic/vgic-mmio-v3.o
> >  obj-y += $(KVM)/arm/vgic/vgic-kvm-device.o
> >  obj-y += $(KVM)/arm/vgic/vgic-its.o
> > +obj-y += $(KVM)/arm/vgic/vgic-debug.o
> >  obj-y += $(KVM)/irqchip.o
> >  obj-y += $(KVM)/arm/arch_timer.o
> > diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
> > index d50a82a..e025bec 100644
> > --- a/arch/arm64/kvm/Makefile
> > +++ b/arch/arm64/kvm/Makefile
> > @@ -31,6 +31,7 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-mmio-v2.o
> >  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-mmio-v3.o
> >  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-kvm-device.o
> >  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-its.o
> > +kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-debug.o
> >  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/irqchip.o
> >  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arch_timer.o
> >  kvm-$(CONFIG_KVM_ARM_PMU) += $(KVM)/arm/pmu.o
> > diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> > index da2ce08..0af1477 100644
> > --- a/include/kvm/arm_vgic.h
> > +++ b/include/kvm/arm_vgic.h
> > @@ -166,6 +166,8 @@ struct vgic_its {
> >  	struct list_head	collection_list;
> >  };
> >  
> > +struct vgic_state_iter;
> > +
> >  struct vgic_dist {
> >  	bool			in_kernel;
> >  	bool			ready;
> > @@ -213,6 +215,9 @@ struct vgic_dist {
> >  	spinlock_t		lpi_list_lock;
> >  	struct list_head	lpi_list_head;
> >  	int			lpi_list_count;
> > +
> > +	/* used by vgic-debug */
> > +	struct vgic_state_iter *iter;
> >  };
> >  
> >  struct vgic_v2_cpu_if {
> > diff --git a/virt/kvm/arm/vgic/vgic-debug.c b/virt/kvm/arm/vgic/vgic-debug.c
> > new file mode 100644
> > index 0000000..ec466a6
> > --- /dev/null
> > +++ b/virt/kvm/arm/vgic/vgic-debug.c
> > @@ -0,0 +1,284 @@
> > +/*
> > + * Copyright (C) 2016 Linaro
> > + * Author: Christoffer Dall <christoffer.dall@linaro.org>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 as
> > + * published by the Free Software Foundation.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> > + * GNU General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> > + */
> > +
> > +#include <linux/cpu.h>
> > +#include <linux/debugfs.h>
> > +#include <linux/interrupt.h>
> > +#include <linux/kvm_host.h>
> > +#include <linux/seq_file.h>
> > +#include <linux/uaccess.h>
> not requested
> > +#include <kvm/arm_vgic.h>
> > +#include <asm/kvm_mmu.h>
> > +#include "vgic.h"
> > +
> > +/*
> > + * Structure to control looping through the entire vgic state.  We start at
> > + * zero for each field and move upwards.  So, if dist_id is 0 we print the
> > + * distributor info.  When dist_id is 1, we have already printed it and move
> > + * on.
> > + *
> > + * When vcpu_id < nr_cpus we print the vcpu info until vcpu_id == nr_cpus and
> > + * so on.
> > + */
> > +struct vgic_state_iter {
> > +	int nr_cpus;
> > +	int nr_spis;
> > +	int dist_id;
> > +	int vcpu_id;
> > +	int intid;
> > +};
> > +
> > +static void iter_next(struct vgic_state_iter *iter)
> > +{
> > +	if (iter->dist_id == 0) {
> > +		iter->dist_id++;
> > +		return;
> > +	}
> > +
> > +	iter->intid++;
> > +	if (iter->intid == VGIC_NR_PRIVATE_IRQS &&
> > +	    ++iter->vcpu_id < iter->nr_cpus)
> > +		iter->intid = 0;
> > +}
> > +
> > +static void iter_init(struct kvm *kvm, struct vgic_state_iter *iter,
> > +		      loff_t pos)
> > +{
> > +	int nr_cpus = atomic_read(&kvm->online_vcpus);
> > +
> > +	memset(iter, 0, sizeof(*iter));
> > +
> > +	iter->nr_cpus = nr_cpus;
> > +	iter->nr_spis = kvm->arch.vgic.nr_spis;
> > +
> > +	/* Fast forward to the right position if needed */
> > +	while (pos--)
> > +		iter_next(iter);
> > +}
> > +
> > +static bool end_of_vgic(struct vgic_state_iter *iter)
> > +{
> > +	return iter->dist_id > 0 &&
> > +		iter->vcpu_id == iter->nr_cpus &&
> > +		(iter->intid - VGIC_NR_PRIVATE_IRQS) == iter->nr_spis;
> > +}
> > +
> > +static void *vgic_debug_start(struct seq_file *s, loff_t *pos)
> > +{
> > +	struct kvm *kvm = (struct kvm *)s->private;
> > +	struct vgic_state_iter *iter;
> > +
> > +	mutex_lock(&kvm->lock);
> > +	iter = kvm->arch.vgic.iter;
> > +	if (iter) {
> > +		iter = ERR_PTR(-EBUSY);
> > +		goto out;
> > +	}
> > +
> > +	iter = kmalloc(sizeof(*iter), GFP_KERNEL);
> > +	if (!iter) {
> > +		iter = ERR_PTR(-ENOMEM);
> > +		goto out;
> > +	}
> > +
> > +	iter_init(kvm, iter, *pos);
> > +	kvm->arch.vgic.iter = iter;
> > +
> > +	if (end_of_vgic(iter))
> > +		iter = NULL;
> > +out:
> > +	mutex_unlock(&kvm->lock);
> > +	return iter;
> > +}
> > +
> > +static void *vgic_debug_next(struct seq_file *s, void *v, loff_t *pos)
> > +{
> > +	struct kvm *kvm = (struct kvm *)s->private;
> > +	struct vgic_state_iter *iter = kvm->arch.vgic.iter;
> > +
> > +	++*pos;
> > +	iter_next(iter);
> > +	if (end_of_vgic(iter))
> > +		iter = NULL;
> > +	return iter;
> > +}
> > +
> > +static void vgic_debug_stop(struct seq_file *s, void *v)
> > +{
> > +	struct kvm *kvm = (struct kvm *)s->private;
> > +	struct vgic_state_iter *iter;
> > +
> > +	/*
> > +	 * If the seq file wasn't properly opened, there's nothing to clearn
> > +	 * up.
> > +	 */
> > +	if (IS_ERR(v))
> > +		return;
> > +
> > +	mutex_lock(&kvm->lock);
> > +	iter = kvm->arch.vgic.iter;
> > +	kfree(iter);
> > +	kvm->arch.vgic.iter = NULL;
> > +	mutex_unlock(&kvm->lock);
> > +}
> > +
> > +static void print_dist_state(struct seq_file *s, struct vgic_dist *dist)
> > +{
> > +	seq_printf(s, "Distributor\n");
> > +	seq_printf(s, "===========\n");
> > +	seq_printf(s, "vgic_model:\t%s\n",
> > +		   (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3) ?
> > +		   "GICv3" : "GICv2");
> > +	seq_printf(s, "nr_spis:\t%d\n", dist->nr_spis);
> > +	seq_printf(s, "enabled:\t%d\n", dist->enabled);
> > +	seq_printf(s, "\n");
> > +
> > +	seq_printf(s, "P=pending, L=line_level, S=soft_pending, A=active\n");
> > +	seq_printf(s, "E=enabled, H=hw, L=config_level\n");
> s/Pending/Pending Latched
> s/S=soft_pending, //
> > +}
> > +
> > +static void print_header(struct seq_file *s, struct vgic_irq *irq,
> > +			 struct kvm_vcpu *vcpu)
> > +{
> > +	int id = 0;
> > +	char *hdr = "SPI ";
> > +
> > +	if (vcpu) {
> > +		hdr = "VCPU";
> > +		id = vcpu->vcpu_id;
> > +	}
> > +
> > +	seq_printf(s, "\n");
> > +	seq_printf(s, "%s%2d TYP   ID TGT_ID PLAEHL     HWID   TARGET SRC PRI VCPU_ID\n", hdr, id);
> > +	seq_printf(s, "---------------------------------------------------------------\n");
> > +}
> > +
> > +static void print_irq_state(struct seq_file *s, struct vgic_irq *irq,
> > +			    struct kvm_vcpu *vcpu)
> > +{
> > +	char *type;
> > +	if (irq->intid < VGIC_NR_SGIS)
> > +		type = "SGI";
> > +	else if (irq->intid < VGIC_NR_PRIVATE_IRQS)
> > +		type = "PPI";
> > +	else
> > +		type = "SPI";
> > +
> > +	if (irq->intid ==0 || irq->intid == VGIC_NR_PRIVATE_IRQS)
> > +		print_header(s, irq, vcpu);
> > +
> > +	seq_printf(s, "       %s %4d "
> > +		      "    %2d "
> > +		      "%d%d%d%d%d%d "
> > +		      "%8x "
> > +		      "%8x "
> > +		      " %2x "
> > +		      " %2x "
> > +		      "     %2d "
> > +		      "\n",
> > +			type, irq->intid,
> > +			(irq->target_vcpu) ? irq->target_vcpu->vcpu_id : -1,
> > +			irq->pending_latch,
> > +			irq->line_level,
> > +			irq->active,
> > +			irq->enabled,
> > +			irq->hw,
> > +			irq->config == VGIC_CONFIG_LEVEL,
> > +			irq->hwintid,
> nit: why not choosing a %4d format like intid?
> > +			irq->mpidr,
> is it set for GICv2?
> > +			irq->source,
> > +			irq->priority,
> nit: decimal format for prio?
> > +			(irq->vcpu) ? irq->vcpu->vcpu_id : -1);
> > +
> > +}
> > +
> > +static int vgic_debug_show(struct seq_file *s, void *v)
> > +{
> > +	struct kvm *kvm = (struct kvm *)s->private;
> > +	struct vgic_state_iter *iter = (struct vgic_state_iter *)v;
> > +	struct vgic_irq *irq;
> > +	struct kvm_vcpu *vcpu = NULL;
> > +
> > +	if (iter->dist_id == 0) {
> > +		print_dist_state(s, &kvm->arch.vgic);
> > +		return 0;
> > +	}
> > +
> > +	if (!kvm->arch.vgic.initialized)
> > +		return 0;
> > +
> > +	if (iter->vcpu_id < iter->nr_cpus) {
> > +		vcpu = kvm_get_vcpu(kvm, iter->vcpu_id);
> > +		irq = &vcpu->arch.vgic_cpu.private_irqs[iter->intid];
> > +	} else {
> > +		irq = &kvm->arch.vgic.spis[iter->intid - VGIC_NR_PRIVATE_IRQS];
> > +	}
> > +
> > +	spin_lock(&irq->irq_lock);
> > +	print_irq_state(s, irq, vcpu);
> > +	spin_unlock(&irq->irq_lock);
> > +
> > +	return 0;
> > +}
> > +
> > +static struct seq_operations vgic_debug_seq_ops = {
> > +	.start = vgic_debug_start,
> > +	.next  = vgic_debug_next,
> > +	.stop  = vgic_debug_stop,
> > +	.show  = vgic_debug_show
> > +};
> > +
> > +static int debug_open(struct inode *inode, struct file *file)
> > +{
> > +	int ret;
> > +	ret = seq_open(file, &vgic_debug_seq_ops);
> > +	if (!ret) {
> > +		struct seq_file *seq;
> > +		/* seq_open will have modified file->private_data */
> > +		seq = file->private_data;
> > +		seq->private = inode->i_private;
> > +	}
> > +
> > +	return ret;
> > +};
> > +
> > +static struct file_operations vgic_debug_fops = {
> > +	.owner   = THIS_MODULE,
> > +	.open    = debug_open,
> > +	.read    = seq_read,
> > +	.llseek  = seq_lseek,
> > +	.release = seq_release
> > +};
> > +
> > +int vgic_debug_init(struct kvm *kvm)
> > +{
> > +	if (!kvm->debugfs_dentry)
> > +		return -ENOENT;
> > +
> > +	if (!debugfs_create_file("vgic-state", 0444,
> > +				 kvm->debugfs_dentry,
> > +				 kvm,
> > +				 &vgic_debug_fops))
> > +		return -ENOMEM;
> > +
> > +	return 0;
> > +}
> > +
> > +int vgic_debug_destroy(struct kvm *kvm)
> > +{
> > +	return 0;
> > +}
> > diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
> > index c737ea0..276139a 100644
> > --- a/virt/kvm/arm/vgic/vgic-init.c
> > +++ b/virt/kvm/arm/vgic/vgic-init.c
> > @@ -259,6 +259,8 @@ int vgic_init(struct kvm *kvm)
> >  	if (ret)
> >  		goto out;
> >  
> > +	vgic_debug_init(kvm);
> > +
> >  	dist->initialized = true;
> >  out:
> >  	return ret;
> > @@ -288,6 +290,8 @@ static void __kvm_vgic_destroy(struct kvm *kvm)
> >  	struct kvm_vcpu *vcpu;
> >  	int i;
> >  
> > +	vgic_debug_destroy(kvm);
> > +
> >  	kvm_vgic_dist_destroy(kvm);
> >  
> >  	kvm_for_each_vcpu(i, vcpu, kvm)
> > diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
> > index b2cf34b..48da1f6 100644
> > --- a/virt/kvm/arm/vgic/vgic.h
> > +++ b/virt/kvm/arm/vgic/vgic.h
> > @@ -102,4 +102,7 @@ int kvm_register_vgic_device(unsigned long type);
> >  int vgic_lazy_init(struct kvm *kvm);
> >  int vgic_init(struct kvm *kvm);
> >  
> > +int vgic_debug_init(struct kvm *kvm);
> > +int vgic_debug_destroy(struct kvm *kvm);
> > +
> >  #endif
> > 
> 
> Besides
> 
> Reviewed-by: Eric Auger <eric.auger@redhat.com>
> Tested-by: Eric Auger <eric.auger@redhat.com>
> 
> Tested on Cavium ThunderX

I've addressed your comments with the following changes:


diff --git a/virt/kvm/arm/vgic/vgic-debug.c b/virt/kvm/arm/vgic/vgic-debug.c
index ec466a6..19c4566 100644
--- a/virt/kvm/arm/vgic/vgic-debug.c
+++ b/virt/kvm/arm/vgic/vgic-debug.c
@@ -20,7 +20,6 @@
 #include <linux/interrupt.h>
 #include <linux/kvm_host.h>
 #include <linux/seq_file.h>
-#include <linux/uaccess.h>
 #include <kvm/arm_vgic.h>
 #include <asm/kvm_mmu.h>
 #include "vgic.h"
@@ -147,8 +146,8 @@ static void print_dist_state(struct seq_file *s, struct vgic_dist *dist)
 	seq_printf(s, "enabled:\t%d\n", dist->enabled);
 	seq_printf(s, "\n");
 
-	seq_printf(s, "P=pending, L=line_level, S=soft_pending, A=active\n");
-	seq_printf(s, "E=enabled, H=hw, L=config_level\n");
+	seq_printf(s, "P=pending_latch, L=line_level, A=active\n");
+	seq_printf(s, "E=enabled, H=hw, C=config (level=1, edge=0)\n");
 }
 
 static void print_header(struct seq_file *s, struct vgic_irq *irq,
@@ -184,10 +183,10 @@ static void print_irq_state(struct seq_file *s, struct vgic_irq *irq,
 	seq_printf(s, "       %s %4d "
 		      "    %2d "
 		      "%d%d%d%d%d%d "
+		      "%8d "
 		      "%8x "
-		      "%8x "
-		      " %2x "
 		      " %2x "
+		      "%3d "
 		      "     %2d "
 		      "\n",
 			type, irq->intid,


Thanks,
-Christoffer