[v4] KVM: s390: Add new reset vcpu API
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Message ID 20191205122810.10672-1-frankja@linux.ibm.com
State New
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  • [v4] KVM: s390: Add new reset vcpu API
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Commit Message

Janosch Frank Dec. 5, 2019, 12:28 p.m. UTC
The architecture states that we need to reset local IRQs for all CPU
resets. Because the old reset interface did not support the normal CPU
reset we never did that. Now that we have a new interface, let's
properly clear out local IRQs.

Also we add a ioctl for the clear reset to have all resets exposed to
userspace. Currently the clear reset falls back to the initial reset,
but we plan to have clear reset specific code in the future.

Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
 Documentation/virt/kvm/api.txt | 48 ++++++++++++++++++++++++++++++++++
 arch/s390/kvm/kvm-s390.c       | 14 ++++++++++
 include/uapi/linux/kvm.h       |  5 ++++
 3 files changed, 67 insertions(+)

Comments

Cornelia Huck Dec. 5, 2019, 12:35 p.m. UTC | #1
On Thu,  5 Dec 2019 07:28:10 -0500
Janosch Frank <frankja@linux.ibm.com> wrote:

> The architecture states that we need to reset local IRQs for all CPU
> resets. Because the old reset interface did not support the normal CPU
> reset we never did that. Now that we have a new interface, let's
> properly clear out local IRQs.
> 
> Also we add a ioctl for the clear reset to have all resets exposed to
> userspace. Currently the clear reset falls back to the initial reset,
> but we plan to have clear reset specific code in the future.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> ---
>  Documentation/virt/kvm/api.txt | 48 ++++++++++++++++++++++++++++++++++
>  arch/s390/kvm/kvm-s390.c       | 14 ++++++++++
>  include/uapi/linux/kvm.h       |  5 ++++
>  3 files changed, 67 insertions(+)
> 
> diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
> index 4833904d32a5..296e51f9df70 100644
> --- a/Documentation/virt/kvm/api.txt
> +++ b/Documentation/virt/kvm/api.txt
> @@ -4126,6 +4126,47 @@ Valid values for 'action':
>  #define KVM_PMU_EVENT_ALLOW 0
>  #define KVM_PMU_EVENT_DENY 1
>  
> +4.121 KVM_S390_NORMAL_RESET
> +
> +Capability: KVM_CAP_S390_VCPU_RESETS
> +Architectures: s390
> +Type: vcpu ioctl
> +Parameters: none
> +Returns: 0
> +
> +This ioctl resets VCPU registers and control structures that userspace
> +can't access via the kvm_run structure. It is intended to be called
> +when a normal reset is performed on the vcpu and clears local
> +interrupts, the riccb and PSW bit 24.
> +
> +4.122 KVM_S390_INITIAL_RESET
> +
> +Capability: none
> +Architectures: s390
> +Type: vcpu ioctl
> +Parameters: none
> +Returns: 0
> +
> +This ioctl resets VCPU registers and control structures that userspace
> +can't access via the kvm_run structure. It is intended to be called
> +when an initial reset (which is a superset of the normal reset) is
> +performed on the vcpu and additionally clears the psw, prefix, timing
> +related registers, as well as setting the control registers to their
> +initial value.
> +
> +4.123 KVM_S390_CLEAR_RESET
> +
> +Capability: KVM_CAP_S390_VCPU_RESETS
> +Architectures: s390
> +Type: vcpu ioctl
> +Parameters: none
> +Returns: 0
> +
> +This ioctl resets VCPU registers and control structures that userspace
> +can't access via the kvm_run structure. It is intended to be called
> +when an initial reset (which is a superset of the normal reset) is

s/initial/clear/
s/normal/initial/

(no need to respin, just fix up while applying :)

> +performed on the vcpu and additionally clears general, access,
> +floating and vector registers.
>  
>  5. The kvm_run structure
>  ------------------------
> @@ -5322,3 +5363,10 @@ handling by KVM (as some KVM hypercall may be mistakenly treated as TLB
>  flush hypercalls by Hyper-V) so userspace should disable KVM identification
>  in CPUID and only exposes Hyper-V identification. In this case, guest
>  thinks it's running on Hyper-V and only use Hyper-V hypercalls.
> +
> +8.22 KVM_CAP_S390_VCPU_RESETS
> +
> +Architectures: s390
> +
> +This capability indicates that the KVM_S390_NORMAL_RESET and
> +KVM_S390_CLEAR_RESET ioctls are available.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Thomas Huth Dec. 5, 2019, 12:50 p.m. UTC | #2
On 05/12/2019 13.28, Janosch Frank wrote:
> The architecture states that we need to reset local IRQs for all CPU
> resets. Because the old reset interface did not support the normal CPU
> reset we never did that. Now that we have a new interface, let's
> properly clear out local IRQs.
> 
> Also we add a ioctl for the clear reset to have all resets exposed to
> userspace. Currently the clear reset falls back to the initial reset,
> but we plan to have clear reset specific code in the future.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> ---
>  Documentation/virt/kvm/api.txt | 48 ++++++++++++++++++++++++++++++++++
>  arch/s390/kvm/kvm-s390.c       | 14 ++++++++++
>  include/uapi/linux/kvm.h       |  5 ++++
>  3 files changed, 67 insertions(+)
[...]
> +4.123 KVM_S390_CLEAR_RESET
> +
> +Capability: KVM_CAP_S390_VCPU_RESETS
> +Architectures: s390
> +Type: vcpu ioctl
> +Parameters: none
> +Returns: 0
> +
> +This ioctl resets VCPU registers and control structures that userspace
> +can't access via the kvm_run structure. It is intended to be called
> +when an initial reset (which is a superset of the normal reset) is
> +performed on the vcpu and additionally clears general, access,
> +floating and vector registers.

So now you've documented that this ioctl clears the GPRs, ARs and
FRs/VRs ... but the implementation does not! That's quite ugly.
Can you please state clearly that it is the job of userspace to clear
these registers (in the default, non-protected case) and that this ioctl
should be called on top?

Same problem with the PSW bit 24 and riccb during normal reset.

Or should the kernel code maybe also clear these in addition to
userspace, just to be in line with the initial reset?

 Thomas

Patch
diff mbox series

diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
index 4833904d32a5..296e51f9df70 100644
--- a/Documentation/virt/kvm/api.txt
+++ b/Documentation/virt/kvm/api.txt
@@ -4126,6 +4126,47 @@  Valid values for 'action':
 #define KVM_PMU_EVENT_ALLOW 0
 #define KVM_PMU_EVENT_DENY 1
 
+4.121 KVM_S390_NORMAL_RESET
+
+Capability: KVM_CAP_S390_VCPU_RESETS
+Architectures: s390
+Type: vcpu ioctl
+Parameters: none
+Returns: 0
+
+This ioctl resets VCPU registers and control structures that userspace
+can't access via the kvm_run structure. It is intended to be called
+when a normal reset is performed on the vcpu and clears local
+interrupts, the riccb and PSW bit 24.
+
+4.122 KVM_S390_INITIAL_RESET
+
+Capability: none
+Architectures: s390
+Type: vcpu ioctl
+Parameters: none
+Returns: 0
+
+This ioctl resets VCPU registers and control structures that userspace
+can't access via the kvm_run structure. It is intended to be called
+when an initial reset (which is a superset of the normal reset) is
+performed on the vcpu and additionally clears the psw, prefix, timing
+related registers, as well as setting the control registers to their
+initial value.
+
+4.123 KVM_S390_CLEAR_RESET
+
+Capability: KVM_CAP_S390_VCPU_RESETS
+Architectures: s390
+Type: vcpu ioctl
+Parameters: none
+Returns: 0
+
+This ioctl resets VCPU registers and control structures that userspace
+can't access via the kvm_run structure. It is intended to be called
+when an initial reset (which is a superset of the normal reset) is
+performed on the vcpu and additionally clears general, access,
+floating and vector registers.
 
 5. The kvm_run structure
 ------------------------
@@ -5322,3 +5363,10 @@  handling by KVM (as some KVM hypercall may be mistakenly treated as TLB
 flush hypercalls by Hyper-V) so userspace should disable KVM identification
 in CPUID and only exposes Hyper-V identification. In this case, guest
 thinks it's running on Hyper-V and only use Hyper-V hypercalls.
+
+8.22 KVM_CAP_S390_VCPU_RESETS
+
+Architectures: s390
+
+This capability indicates that the KVM_S390_NORMAL_RESET and
+KVM_S390_CLEAR_RESET ioctls are available.
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index d9e6bf3d54f0..7f3ede0b2715 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -529,6 +529,7 @@  int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_S390_CMMA_MIGRATION:
 	case KVM_CAP_S390_AIS:
 	case KVM_CAP_S390_AIS_MIGRATION:
+	case KVM_CAP_S390_VCPU_RESETS:
 		r = 1;
 		break;
 	case KVM_CAP_S390_HPAGE_1M:
@@ -3287,6 +3288,13 @@  static int kvm_arch_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu,
 	return r;
 }
 
+static int kvm_arch_vcpu_ioctl_normal_reset(struct kvm_vcpu *vcpu)
+{
+	kvm_clear_async_pf_completion_queue(vcpu);
+	kvm_s390_clear_local_irqs(vcpu);
+	return 0;
+}
+
 static int kvm_arch_vcpu_ioctl_initial_reset(struct kvm_vcpu *vcpu)
 {
 	kvm_s390_vcpu_initial_reset(vcpu);
@@ -4363,9 +4371,15 @@  long kvm_arch_vcpu_ioctl(struct file *filp,
 		r = kvm_arch_vcpu_ioctl_set_initial_psw(vcpu, psw);
 		break;
 	}
+
+	case KVM_S390_CLEAR_RESET:
+		/* fallthrough */
 	case KVM_S390_INITIAL_RESET:
 		r = kvm_arch_vcpu_ioctl_initial_reset(vcpu);
 		break;
+	case KVM_S390_NORMAL_RESET:
+		r = kvm_arch_vcpu_ioctl_normal_reset(vcpu);
+		break;
 	case KVM_SET_ONE_REG:
 	case KVM_GET_ONE_REG: {
 		struct kvm_one_reg reg;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 52641d8ca9e8..edbb2da43f02 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1000,6 +1000,7 @@  struct kvm_ppc_resize_hpt {
 #define KVM_CAP_PMU_EVENT_FILTER 173
 #define KVM_CAP_ARM_IRQ_LINE_LAYOUT_2 174
 #define KVM_CAP_HYPERV_DIRECT_TLBFLUSH 175
+#define KVM_CAP_S390_VCPU_RESETS 176
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
@@ -1461,6 +1462,10 @@  struct kvm_enc_region {
 /* Available with KVM_CAP_ARM_SVE */
 #define KVM_ARM_VCPU_FINALIZE	  _IOW(KVMIO,  0xc2, int)
 
+/* Available with  KVM_CAP_S390_VCPU_RESETS */
+#define KVM_S390_NORMAL_RESET	_IO(KVMIO,   0xc3)
+#define KVM_S390_CLEAR_RESET	_IO(KVMIO,   0xc4)
+
 /* Secure Encrypted Virtualization command */
 enum sev_cmd_id {
 	/* Guest initialization commands */