Re: [PATCH 7/9] kvm: s390: Add CPU dump functionality

Janosch Frank <frankja@xxxxxxxxxxxxx> · Tue, 10 May 2022 09:26:50 +0200

On 5/9/22 21:11, Claudio Imbrenda wrote:
On Thu, 28 Apr 2022 13:01:00 +0000
Janosch Frank <frankja@xxxxxxxxxxxxx> wrote:

The previous patch introduced the per-VM dump functions now let's
focus on dumping the VCPU state via the newly introduced
KVM_S390_PV_CPU_COMMAND ioctl which mirrors the VM UV ioctl and can be
extended with new commands later.

Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
---
  arch/s390/kvm/kvm-s390.c | 73 ++++++++++++++++++++++++++++++++++++++++
  arch/s390/kvm/kvm-s390.h |  1 +
  arch/s390/kvm/pv.c       | 16 +++++++++
  include/uapi/linux/kvm.h |  5 +++
  4 files changed, 95 insertions(+)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 8984e8db33b4..d15ce38bef14 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -5149,6 +5149,52 @@ long kvm_arch_vcpu_async_ioctl(struct file *filp,
  	return -ENOIOCTLCMD;
  }
  
+static int kvm_s390_handle_pv_vcpu_dump(struct kvm_vcpu *vcpu,
+					struct kvm_pv_cmd *cmd)
+{
+	struct kvm_s390_pv_dmp dmp;
+	void *data;
+	int ret;
+
+	/* Dump initialization is a prerequisite */
+	if (!vcpu->kvm->arch.pv.dumping)
+		return -EINVAL;
+
+	if (copy_from_user(&dmp, (__u8 __user *)cmd->data, sizeof(dmp)))
+		return -EFAULT;
+
+	/* We only handle this subcmd right now */
+	if (dmp.subcmd != KVM_PV_DUMP_CPU)
+		return -EINVAL;
+
+	/* CPU dump length is the same as create cpu storage donation. */
+	if (dmp.buff_len != uv_info.guest_cpu_stor_len)
+		return -EINVAL;
+
+	data = vzalloc(uv_info.guest_cpu_stor_len);
+	if (!data)
+		return -ENOMEM;
+
+	ret = kvm_s390_pv_dump_cpu(vcpu, data, &cmd->rc, &cmd->rrc);
+
+	VCPU_EVENT(vcpu, 3, "PROTVIRT DUMP CPU %d rc %x rrc %x",
+		   vcpu->vcpu_id, cmd->rc, cmd->rrc);
+
+	if (ret) {
+		vfree(data);
+		return -EINVAL;
+	}
+
+	/* On success copy over the dump data */
+	if (copy_to_user((__u8 __user *)dmp.buff_addr, data, uv_info.guest_cpu_stor_len)) {
+		vfree(data);
+		return -EFAULT;
+	}
+
+	vfree(data);
+	return 0;
+}
+
  long kvm_arch_vcpu_ioctl(struct file *filp,
  			 unsigned int ioctl, unsigned long arg)
  {
@@ -5313,6 +5359,33 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
  					   irq_state.len);
  		break;
  	}
+	case KVM_S390_PV_CPU_COMMAND: {
+		struct kvm_pv_cmd cmd;
+
+		r = -EINVAL;
+		if (!is_prot_virt_host())
+			break;
+
+		r = -EFAULT;
+		if (copy_from_user(&cmd, argp, sizeof(cmd)))
+			break;
+
+		r = -EINVAL;
+		if (cmd.flags)
+			break;
+
+		/* We only handle this cmd right now */
+		if (cmd.cmd != KVM_PV_DUMP)
+			break;
+
+		r = kvm_s390_handle_pv_vcpu_dump(vcpu, &cmd);
+
+		/* Always copy over UV rc / rrc data */
+		if (copy_to_user((__u8 __user *)argp, &cmd.rc,
+				 sizeof(cmd.rc) + sizeof(cmd.rrc)))
+			r = -EFAULT;
+		break;
+	}
  	default:
  		r = -ENOTTY;
  	}
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index 2868dd0bba25..a39815184350 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -250,6 +250,7 @@ int kvm_s390_pv_set_sec_parms(struct kvm *kvm, void *hdr, u64 length, u16 *rc,
  int kvm_s390_pv_unpack(struct kvm *kvm, unsigned long addr, unsigned long size,
  		       unsigned long tweak, u16 *rc, u16 *rrc);
  int kvm_s390_pv_set_cpu_state(struct kvm_vcpu *vcpu, u8 state);
+int kvm_s390_pv_dump_cpu(struct kvm_vcpu *vcpu, void *buff, u16 *rc, u16 *rrc);
  int kvm_s390_pv_dump_stor_state(struct kvm *kvm, void __user *buff_user,
  				u64 *gaddr, u64 buff_user_len, u16 *rc, u16 *rrc);
  
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index d1635ed50078..9ab8192b9b23 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -299,6 +299,22 @@ int kvm_s390_pv_set_cpu_state(struct kvm_vcpu *vcpu, u8 state)
  	return 0;
  }
  
+int kvm_s390_pv_dump_cpu(struct kvm_vcpu *vcpu, void *buff, u16 *rc, u16 *rrc)
+{
+	struct uv_cb_dump_cpu uvcb = {
+		.header.cmd = UVC_CMD_DUMP_CPU,
+		.header.len = sizeof(uvcb),
+		.cpu_handle = vcpu->arch.pv.handle,
+		.dump_area_origin = (u64)buff,
+	};
+	int cc;
+
+	cc = uv_call_sched(0, (u64)&uvcb);

it's a small amount of data, but you use the _sched variant?

Who knows what FW will do :)


and, why aren't you using the _sched variant in the previous patch (for
DUMP_COMPLETE)?

to be clear: I think the right thing is to always use the _sched
variant unless there is a good reason not to (so please fix the previous
patch)

Yep, will fix.

It might make sense to switch the functions around and make uv_call 
always do a sched and introduce uv_call_nosched() since that's the 
special case. But that's something for the future.


+	*rc = uvcb.header.rc;
+	*rrc = uvcb.header.rrc;
+	return cc;
+}
+
  /* Size of the cache for the storage state dump data. 1MB for now */
  #define DUMP_BUFF_LEN HPAGE_SIZE
  
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index b34850907291..108bc7b7a71b 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1144,6 +1144,7 @@ struct kvm_ppc_resize_hpt {
  #define KVM_CAP_S390_MEM_OP_EXTENSION 211
  #define KVM_CAP_PMU_CAPABILITY 212
  #define KVM_CAP_DISABLE_QUIRKS2 213
+#define KVM_CAP_S390_PROTECTED_DUMP 214
  
  #ifdef KVM_CAP_IRQ_ROUTING
  
@@ -1649,6 +1650,7 @@ enum pv_cmd_dmp_id {
  	KVM_PV_DUMP_INIT,
  	KVM_PV_DUMP_CONFIG_STOR_STATE,
  	KVM_PV_DUMP_COMPLETE,
+	KVM_PV_DUMP_CPU,
  };
  
  struct kvm_s390_pv_dmp {
@@ -2110,4 +2112,7 @@ struct kvm_stats_desc {
  /* Available with KVM_CAP_XSAVE2 */
  #define KVM_GET_XSAVE2		  _IOR(KVMIO,  0xcf, struct kvm_xsave)
  
+/* Available with KVM_CAP_S390_PROTECTED_DUMP */
+#define KVM_S390_PV_CPU_COMMAND	_IOWR(KVMIO, 0xd0, struct kvm_pv_cmd)
+
  #endif /* __LINUX_KVM_H */








