Re: [PATCH 2/2] Detect vGIC presence at runtime
On Tue, Jul 07, 2015 at 02:11:01PM +0300, Pavel Fedin wrote:
Allows to use KVM on hardware without vGIC. Interrupt controller has to be
emulated in userspace in this case.
Signed-off-by: Pavel Fedin p.fe...@samsung.com
---
arch/arm/kvm/arm.c | 19 ++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index d9631ec..f2f7a13 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -61,6 +61,8 @@ static atomic64_t kvm_vmid_gen = ATOMIC64_INIT(1);
static u8 kvm_next_vmid;
static DEFINE_SPINLOCK(kvm_vmid_lock);
+static bool vgic_present;
+
static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
{
BUG_ON(preemptible());
@@ -172,6 +174,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long
ext)
switch (ext) {
case KVM_CAP_IRQCHIP:
case KVM_CAP_IRQFD:
+ r = vgic_present;
+ break;
case KVM_CAP_IOEVENTFD:
case KVM_CAP_DEVICE_CTRL:
case KVM_CAP_USER_MEMORY:
@@ -850,6 +854,8 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
switch (dev_id) {
case KVM_ARM_DEVICE_VGIC_V2:
+ if (!vgic_present)
+ return -ENXIO;
return kvm_vgic_addr(kvm, type, dev_addr-addr, true);
default:
return -ENODEV;
@@ -864,6 +870,8 @@ long kvm_arch_vm_ioctl(struct file *filp,
switch (ioctl) {
case KVM_CREATE_IRQCHIP: {
+ if (!vgic_present)
+ return -ENXIO;
return kvm_vgic_create(kvm, KVM_DEV_TYPE_ARM_VGIC_V2);
}
case KVM_ARM_SET_DEVICE_ADDR: {
@@ -1046,8 +1054,17 @@ static int init_hyp_mode(void)
* Init HYP view of VGIC
*/
err = kvm_vgic_hyp_init();
- if (err)
+ switch (err) {
+ case 0:
+ vgic_present = true;
+ break;
+ case -ENODEV:
+ case -ENXIO:
+ vgic_present = false;
why not report ENXIO as an error? If probing the vgic fails due to
being unable to request the irq or something similar, then surely your
system has and error and this should be reported.
This may be more nicely implemented by letting the vgic init/probe
functions set the vgic_present, or maybe better yet, just export a
function from vgic.c:
bool kvm_vgic_present(void)
{
return vgic_ops != NULL;
}
+ break;
+ default:
goto out_free_context;
+ }
/*
* Init HYP architected timer support
--
2.4.4
-Christoffer
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RE: [PATCH 2/2] Detect vGIC presence at runtime
Hello!
why not report ENXIO as an error? If probing the vgic fails due to
being unable to request the irq or something similar, then surely your
system has and error and this should be reported.
It is reported by probe function itself.
-ENODEV here means there's no GIC at all. -ENXIO happens when, for example,
there is GIC node in
the device tree, but it does not specify vGIC resources. Normally this means
that vGIC is defunct on
the machine.
This may be more nicely implemented by letting the vgic init/probe
functions set the vgic_present, or maybe better yet, just export a
function from vgic.c:
bool kvm_vgic_present(void)
{
return vgic_ops != NULL;
}
Is it necessary? Actually this flag is not needed anywhere else except
arch/arm/kvm/arm.c, only at
init time. Runtime should, i believe, use irqchip_in_kernel(), because userland
can choose just not
to use vGIC for some reason (testing for example).
Kind regards,
Pavel Fedin
Expert Engineer
Samsung Electronics Research center Russia
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Re: [PATCH 2/2] Detect vGIC presence at runtime
On Thu, Jul 09, 2015 at 03:50:49PM +0300, Pavel Fedin wrote:
Hello!
why not report ENXIO as an error? If probing the vgic fails due to
being unable to request the irq or something similar, then surely your
system has and error and this should be reported.
It is reported by probe function itself.
-ENODEV here means there's no GIC at all. -ENXIO happens when, for example,
there is GIC node in
the device tree, but it does not specify vGIC resources. Normally this means
that vGIC is defunct on
the machine.
I'd like to distinguish between the 'missing vgic' and 'something bad
happened when trying to initialize the vgic' cases, which I don't think
we do currently, because the ENXIO code is used in various situations.
This may be more nicely implemented by letting the vgic init/probe
functions set the vgic_present, or maybe better yet, just export a
function from vgic.c:
bool kvm_vgic_present(void)
{
return vgic_ops != NULL;
}
Is it necessary? Actually this flag is not needed anywhere else except
arch/arm/kvm/arm.c, only at
init time. Runtime should, i believe, use irqchip_in_kernel(), because
userland can choose just not
to use vGIC for some reason (testing for example).
I feel the init flow is relatively difficult to follow and adding a
bunch of flags here and there doesn't seem to help. By adding a
function with a proper comment, it should be more clear, and I don't
like the switch statement on the error return values.
-Christoffer
--
To unsubscribe from this list: send the line unsubscribe kvm in
the body of a message to majord...@vger.kernel.org
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RE: [PATCH 2/2] Detect vGIC presence at runtime
Hello!
I'd like to distinguish between the 'missing vgic' and 'something bad
happened when trying to initialize the vgic' cases, which I don't think
we do currently, because the ENXIO code is used in various situations.
It is done. Check, for example, vgic_v2_probe(). -ENXIO is returned when some
of resources are
either missing from DT specification or wrongly given (not page-aligned). In
the rest of cases error
code is taken from underlying functions, which are more supposed to return
things like -EINVAL or
-ENOMEM.
If you are doubtful, i could suggest to replace -EINVAL with -ENODEV in cases
where resources are
not present. This would give more clear indication of we don't have vGIC
condition.
I feel the init flow is relatively difficult to follow and adding a
bunch of flags here and there doesn't seem to help. By adding a
function with a proper comment, it should be more clear, and I don't
like the switch statement on the error return values.
Well, the alternative is:
1. If GIC node or vGIC resources are not present, return 0 instead of error
code.
2. Implement a function which you suggest.
Then:
1. Situation with missing vGIC is just considered to be normal; it's not a
to-be-ignored error any
more.
2. vGIC present situation is automatically determined by vgic_ops != NULL;
this means that probe
function completely worked and vGIC implementation has been chosen.
Agree?
Kind regards,
Pavel Fedin
Expert Engineer
Samsung Electronics Research center Russia
-Original Message-
From: Christoffer Dall [mailto:christoffer.d...@linaro.org]
Sent: Thursday, July 09, 2015 4:25 PM
To: Pavel Fedin
Cc: kvm...@lists.cs.columbia.edu; kvm@vger.kernel.org; 'Marc Zyngier'
Subject: Re: [PATCH 2/2] Detect vGIC presence at runtime
On Thu, Jul 09, 2015 at 03:50:49PM +0300, Pavel Fedin wrote:
Hello!
why not report ENXIO as an error? If probing the vgic fails due to
being unable to request the irq or something similar, then surely your
system has and error and this should be reported.
It is reported by probe function itself.
-ENODEV here means there's no GIC at all. -ENXIO happens when, for
example, there is GIC node
in
the device tree, but it does not specify vGIC resources. Normally this
means that vGIC is
defunct on
the machine.
This may be more nicely implemented by letting the vgic init/probe
functions set the vgic_present, or maybe better yet, just export a
function from vgic.c:
bool kvm_vgic_present(void)
{
return vgic_ops != NULL;
}
Is it necessary? Actually this flag is not needed anywhere else except
arch/arm/kvm/arm.c, only
at
init time. Runtime should, i believe, use irqchip_in_kernel(), because
userland can choose just
not
to use vGIC for some reason (testing for example).
I feel the init flow is relatively difficult to follow and adding a
bunch of flags here and there doesn't seem to help. By adding a
function with a proper comment, it should be more clear, and I don't
like the switch statement on the error return values.
-Christoffer
--
To unsubscribe from this list: send the line unsubscribe kvm in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH 2/2] Detect vGIC presence at runtime
Allows to use KVM on hardware without vGIC. Interrupt controller has to be
emulated in userspace in this case.
Signed-off-by: Pavel Fedin p.fe...@samsung.com
---
arch/arm/kvm/arm.c | 19 ++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index d9631ec..f2f7a13 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -61,6 +61,8 @@ static atomic64_t kvm_vmid_gen = ATOMIC64_INIT(1);
static u8 kvm_next_vmid;
static DEFINE_SPINLOCK(kvm_vmid_lock);
+static bool vgic_present;
+
static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
{
BUG_ON(preemptible());
@@ -172,6 +174,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
switch (ext) {
case KVM_CAP_IRQCHIP:
case KVM_CAP_IRQFD:
+ r = vgic_present;
+ break;
case KVM_CAP_IOEVENTFD:
case KVM_CAP_DEVICE_CTRL:
case KVM_CAP_USER_MEMORY:
@@ -850,6 +854,8 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
switch (dev_id) {
case KVM_ARM_DEVICE_VGIC_V2:
+ if (!vgic_present)
+ return -ENXIO;
return kvm_vgic_addr(kvm, type, dev_addr-addr, true);
default:
return -ENODEV;
@@ -864,6 +870,8 @@ long kvm_arch_vm_ioctl(struct file *filp,
switch (ioctl) {
case KVM_CREATE_IRQCHIP: {
+ if (!vgic_present)
+ return -ENXIO;
return kvm_vgic_create(kvm, KVM_DEV_TYPE_ARM_VGIC_V2);
}
case KVM_ARM_SET_DEVICE_ADDR: {
@@ -1046,8 +1054,17 @@ static int init_hyp_mode(void)
* Init HYP view of VGIC
*/
err = kvm_vgic_hyp_init();
- if (err)
+ switch (err) {
+ case 0:
+ vgic_present = true;
+ break;
+ case -ENODEV:
+ case -ENXIO:
+ vgic_present = false;
+ break;
+ default:
goto out_free_context;
+ }
/*
* Init HYP architected timer support
--
2.4.4
--
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