[RFC,v2,3/3] virt: Check KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 for smp_cpus > 256
diff mbox series

Message ID 20190911155125.11932-4-eric.auger@redhat.com
State New
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Series
  • KVM/ARM: Fix >256 vcpus
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Commit Message

Eric Auger Sept. 11, 2019, 3:51 p.m. UTC
Host kernel within [4.18, 5.3] report an erroneous KVM_MAX_VCPUS=512
for ARM. The actual capability to instantiate more than 256 vcpus
was fixed in 5.4 with the upgrade of the KVM_IRQ_LINE ABI to support
vcpu id encoded on 12 bits instead of 8 and a redistributor consuming
a single KVM IO device instead of 2.

So let's check this capability when attempting to use more than 256
vcpus.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
---
 hw/arm/virt.c        |  4 ++++
 target/arm/kvm.c     | 21 +++++++++++++++++++++
 target/arm/kvm_arm.h | 15 +++++++++++++++
 3 files changed, 40 insertions(+)

Comments

Andrew Jones Sept. 12, 2019, 7:40 a.m. UTC | #1
On Wed, Sep 11, 2019 at 05:51:25PM +0200, Eric Auger wrote:
> Host kernel within [4.18, 5.3] report an erroneous KVM_MAX_VCPUS=512
> for ARM. The actual capability to instantiate more than 256 vcpus
> was fixed in 5.4 with the upgrade of the KVM_IRQ_LINE ABI to support
> vcpu id encoded on 12 bits instead of 8 and a redistributor consuming
> a single KVM IO device instead of 2.
> 
> So let's check this capability when attempting to use more than 256
> vcpus.
> 
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> ---
>  hw/arm/virt.c        |  4 ++++
>  target/arm/kvm.c     | 21 +++++++++++++++++++++
>  target/arm/kvm_arm.h | 15 +++++++++++++++
>  3 files changed, 40 insertions(+)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 0d1629ccb3..465e3140f7 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -1575,6 +1575,10 @@ static void machvirt_init(MachineState *machine)
>          virt_max_cpus = GIC_NCPU;
>      }
>  
> +    if (kvm_arm_irq_line_layout_mismatch(MACHINE(vms), max_cpus)) {
> +        exit(1);
> +    }
> +
>      if (max_cpus > virt_max_cpus) {
>          error_report("Number of SMP CPUs requested (%d) exceeds max CPUs "
>                       "supported by machine 'mach-virt' (%d)",
> diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> index 6cdfa2204f..b601e2f35a 100644
> --- a/target/arm/kvm.c
> +++ b/target/arm/kvm.c
> @@ -171,6 +171,27 @@ bool kvm_arm_pmu_supported(CPUState *cpu)
>      return kvm_check_extension(s, KVM_CAP_ARM_PMU_V3);
>  }
>  
> +bool kvm_arm_irq_line_layout_mismatch(MachineState *ms, int vcpus)
> +{
> +    KVMState *s;
> +    bool ret;
> +
> +    if (!kvm_enabled()) {
> +        return false;
> +    }
> +
> +    s = KVM_STATE(ms->accelerator);
> +
> +    ret = vcpus > 256 &&
> +          !kvm_check_extension(s, KVM_CAP_ARM_IRQ_LINE_LAYOUT_2);
> +
> +    if (ret) {
> +        error_report("Using more than 256 vcpus requires a host kernel "
> +                     "with KVM_CAP_ARM_IRQ_LINE_LAYOUT_2");
> +    }
> +    return ret;
> +}
> +
>  int kvm_arm_get_max_vm_ipa_size(MachineState *ms)
>  {
>      KVMState *s = KVM_STATE(ms->accelerator);
> diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
> index b4e19457a0..d893d950d8 100644
> --- a/target/arm/kvm_arm.h
> +++ b/target/arm/kvm_arm.h
> @@ -233,6 +233,16 @@ bool kvm_arm_pmu_supported(CPUState *cs);
>   */
>  int kvm_arm_get_max_vm_ipa_size(MachineState *ms);
>  
> +/**
> + * kvm_arm_irq_line_layout_mismatch - Returns whether the number of vcpus
> + * exceeds the limit imposed by the legacy KVM_IRQ_LINE ARM layout
> + * (without the vcpu2_index field).
> + *
> + * @ms: Machine state handle
> + * @vcpus: number of vcpus
> + */
> +bool kvm_arm_irq_line_layout_mismatch(MachineState *ms, int vcpus);
> +
>  /**
>   * kvm_arm_sync_mpstate_to_kvm
>   * @cpu: ARMCPU
> @@ -281,6 +291,11 @@ static inline int kvm_arm_get_max_vm_ipa_size(MachineState *ms)
>      return -ENOENT;
>  }
>  
> +static inline bool kvm_arm_irq_line_layout_mismatch(MachineState *ms, int vcpus)
> +{
> +    return false;
> +}
> +
>  static inline int kvm_arm_vgic_probe(void)
>  {
>      return 0;
> -- 
> 2.20.1
> 
>

Reviewed-by: Andrew Jones <drjones@redhat.com>
Peter Maydell Sept. 12, 2019, 8:42 a.m. UTC | #2
On Wed, 11 Sep 2019 at 16:51, Eric Auger <eric.auger@redhat.com> wrote:
>
> Host kernel within [4.18, 5.3] report an erroneous KVM_MAX_VCPUS=512
> for ARM. The actual capability to instantiate more than 256 vcpus
> was fixed in 5.4 with the upgrade of the KVM_IRQ_LINE ABI to support
> vcpu id encoded on 12 bits instead of 8 and a redistributor consuming
> a single KVM IO device instead of 2.
>
> So let's check this capability when attempting to use more than 256
> vcpus.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> ---
>  hw/arm/virt.c        |  4 ++++
>  target/arm/kvm.c     | 21 +++++++++++++++++++++
>  target/arm/kvm_arm.h | 15 +++++++++++++++
>  3 files changed, 40 insertions(+)
>
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 0d1629ccb3..465e3140f7 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -1575,6 +1575,10 @@ static void machvirt_init(MachineState *machine)
>          virt_max_cpus = GIC_NCPU;
>      }
>
> +    if (kvm_arm_irq_line_layout_mismatch(MACHINE(vms), max_cpus)) {
> +        exit(1);
> +    }
> +

Is there really no place to put this check in common code?

thanks
-- PMM
Eric Auger Sept. 12, 2019, 8:57 a.m. UTC | #3
Hi Peter,
On 9/12/19 10:42 AM, Peter Maydell wrote:
> On Wed, 11 Sep 2019 at 16:51, Eric Auger <eric.auger@redhat.com> wrote:
>>
>> Host kernel within [4.18, 5.3] report an erroneous KVM_MAX_VCPUS=512
>> for ARM. The actual capability to instantiate more than 256 vcpus
>> was fixed in 5.4 with the upgrade of the KVM_IRQ_LINE ABI to support
>> vcpu id encoded on 12 bits instead of 8 and a redistributor consuming
>> a single KVM IO device instead of 2.
>>
>> So let's check this capability when attempting to use more than 256
>> vcpus.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>> ---
>>  hw/arm/virt.c        |  4 ++++
>>  target/arm/kvm.c     | 21 +++++++++++++++++++++
>>  target/arm/kvm_arm.h | 15 +++++++++++++++
>>  3 files changed, 40 insertions(+)
>>
>> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
>> index 0d1629ccb3..465e3140f7 100644
>> --- a/hw/arm/virt.c
>> +++ b/hw/arm/virt.c
>> @@ -1575,6 +1575,10 @@ static void machvirt_init(MachineState *machine)
>>          virt_max_cpus = GIC_NCPU;
>>      }
>>
>> +    if (kvm_arm_irq_line_layout_mismatch(MACHINE(vms), max_cpus)) {
>> +        exit(1);
>> +    }
>> +
> 
> Is there really no place to put this check in common code?
Not sure what you mean by common code here? Do you mean in a common code
for ARM machines (I don't think we have any atm) or directly in
kvm_init(). I did not want to pollute this latter with this ARM specific
fix.

Thanks

Eric

> 
> thanks
> -- PMM
>
Peter Maydell Sept. 12, 2019, 9 a.m. UTC | #4
On Thu, 12 Sep 2019 at 09:57, Auger Eric <eric.auger@redhat.com> wrote:
>
> Hi Peter,
> On 9/12/19 10:42 AM, Peter Maydell wrote:

> > Is there really no place to put this check in common code?

> Not sure what you mean by common code here? Do you mean in a common code
> for ARM machines (I don't think we have any atm) or directly in
> kvm_init(). I did not want to pollute this latter with this ARM specific
> fix.

I'd just rather we didn't have to have the same "if ..." check
in every arm board that supports KVM.

If kvm_init() happens at a point where we have enough info to
make the check, then you can put the check in kvm_arch_init(),
which is the architecture-specific hook that kvm_init() calls.

thanks
-- PMM
Eric Auger Sept. 12, 2019, 9:27 a.m. UTC | #5
Hi Peter,
On 9/12/19 11:00 AM, Peter Maydell wrote:
> On Thu, 12 Sep 2019 at 09:57, Auger Eric <eric.auger@redhat.com> wrote:
>>
>> Hi Peter,
>> On 9/12/19 10:42 AM, Peter Maydell wrote:
> 
>>> Is there really no place to put this check in common code?
> 
>> Not sure what you mean by common code here? Do you mean in a common code
>> for ARM machines (I don't think we have any atm) or directly in
>> kvm_init(). I did not want to pollute this latter with this ARM specific
>> fix.
> 
> I'd just rather we didn't have to have the same "if ..." check
> in every arm board that supports KVM.
> 
> If kvm_init() happens at a point where we have enough info to
> make the check, then you can put the check in kvm_arch_init(),
> which is the architecture-specific hook that kvm_init() calls.
OK Thank you for the hint. It should be OK.

Thanks!

Eric

> 
> thanks
> -- PMM
>

Patch
diff mbox series

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 0d1629ccb3..465e3140f7 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -1575,6 +1575,10 @@  static void machvirt_init(MachineState *machine)
         virt_max_cpus = GIC_NCPU;
     }
 
+    if (kvm_arm_irq_line_layout_mismatch(MACHINE(vms), max_cpus)) {
+        exit(1);
+    }
+
     if (max_cpus > virt_max_cpus) {
         error_report("Number of SMP CPUs requested (%d) exceeds max CPUs "
                      "supported by machine 'mach-virt' (%d)",
diff --git a/target/arm/kvm.c b/target/arm/kvm.c
index 6cdfa2204f..b601e2f35a 100644
--- a/target/arm/kvm.c
+++ b/target/arm/kvm.c
@@ -171,6 +171,27 @@  bool kvm_arm_pmu_supported(CPUState *cpu)
     return kvm_check_extension(s, KVM_CAP_ARM_PMU_V3);
 }
 
+bool kvm_arm_irq_line_layout_mismatch(MachineState *ms, int vcpus)
+{
+    KVMState *s;
+    bool ret;
+
+    if (!kvm_enabled()) {
+        return false;
+    }
+
+    s = KVM_STATE(ms->accelerator);
+
+    ret = vcpus > 256 &&
+          !kvm_check_extension(s, KVM_CAP_ARM_IRQ_LINE_LAYOUT_2);
+
+    if (ret) {
+        error_report("Using more than 256 vcpus requires a host kernel "
+                     "with KVM_CAP_ARM_IRQ_LINE_LAYOUT_2");
+    }
+    return ret;
+}
+
 int kvm_arm_get_max_vm_ipa_size(MachineState *ms)
 {
     KVMState *s = KVM_STATE(ms->accelerator);
diff --git a/target/arm/kvm_arm.h b/target/arm/kvm_arm.h
index b4e19457a0..d893d950d8 100644
--- a/target/arm/kvm_arm.h
+++ b/target/arm/kvm_arm.h
@@ -233,6 +233,16 @@  bool kvm_arm_pmu_supported(CPUState *cs);
  */
 int kvm_arm_get_max_vm_ipa_size(MachineState *ms);
 
+/**
+ * kvm_arm_irq_line_layout_mismatch - Returns whether the number of vcpus
+ * exceeds the limit imposed by the legacy KVM_IRQ_LINE ARM layout
+ * (without the vcpu2_index field).
+ *
+ * @ms: Machine state handle
+ * @vcpus: number of vcpus
+ */
+bool kvm_arm_irq_line_layout_mismatch(MachineState *ms, int vcpus);
+
 /**
  * kvm_arm_sync_mpstate_to_kvm
  * @cpu: ARMCPU
@@ -281,6 +291,11 @@  static inline int kvm_arm_get_max_vm_ipa_size(MachineState *ms)
     return -ENOENT;
 }
 
+static inline bool kvm_arm_irq_line_layout_mismatch(MachineState *ms, int vcpus)
+{
+    return false;
+}
+
 static inline int kvm_arm_vgic_probe(void)
 {
     return 0;