Re: [PATCH v14 5/6] KVM: s390: pv: support for Destroy fast UVC

Steffen Eiden <seiden@xxxxxxxxxxxxx> · Tue, 4 Oct 2022 15:48:02 +0200

On 9/30/22 16:01, Claudio Imbrenda wrote:
Add support for the Destroy Secure Configuration Fast Ultravisor call,
and take advantage of it for asynchronous destroy.

When supported, the protected guest is destroyed immediately using the
new UVC, leaving only the memory to be cleaned up asynchronously.

Signed-off-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Reviewed-by: Nico Boehr <nrb@xxxxxxxxxxxxx>
Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
LGTM
Reviewed-by: Steffen Eiden <seiden@xxxxxxxxxxxxx>

---
  arch/s390/include/asm/uv.h | 10 +++++++
  arch/s390/kvm/pv.c         | 57 ++++++++++++++++++++++++++++++++------
  2 files changed, 59 insertions(+), 8 deletions(-)

diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
index be3ef9dd6972..28a9ad57b6f1 100644
--- a/arch/s390/include/asm/uv.h
+++ b/arch/s390/include/asm/uv.h
@@ -34,6 +34,7 @@
  #define UVC_CMD_INIT_UV			0x000f
  #define UVC_CMD_CREATE_SEC_CONF		0x0100
  #define UVC_CMD_DESTROY_SEC_CONF	0x0101
+#define UVC_CMD_DESTROY_SEC_CONF_FAST	0x0102
  #define UVC_CMD_CREATE_SEC_CPU		0x0120
  #define UVC_CMD_DESTROY_SEC_CPU		0x0121
  #define UVC_CMD_CONV_TO_SEC_STOR	0x0200
@@ -81,6 +82,7 @@ enum uv_cmds_inst {
  	BIT_UVC_CMD_UNSHARE_ALL = 20,
  	BIT_UVC_CMD_PIN_PAGE_SHARED = 21,
  	BIT_UVC_CMD_UNPIN_PAGE_SHARED = 22,
+	BIT_UVC_CMD_DESTROY_SEC_CONF_FAST = 23,
  	BIT_UVC_CMD_DUMP_INIT = 24,
  	BIT_UVC_CMD_DUMP_CONFIG_STOR_STATE = 25,
  	BIT_UVC_CMD_DUMP_CPU = 26,
@@ -230,6 +232,14 @@ struct uv_cb_nodata {
  	u64 reserved20[4];
  } __packed __aligned(8);
  
+/* Destroy Configuration Fast */
+struct uv_cb_destroy_fast {
+	struct uv_cb_header header;
+	u64 reserved08[2];
+	u64 handle;
+	u64 reserved20[5];
+} __packed __aligned(8);
+
  /* Set Shared Access */
  struct uv_cb_share {
  	struct uv_cb_header header;
diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
index 335eeec6e3da..1b51e5c3f7df 100644
--- a/arch/s390/kvm/pv.c
+++ b/arch/s390/kvm/pv.c
@@ -201,6 +201,9 @@ static int kvm_s390_pv_dispose_one_leftover(struct kvm *kvm,
  {
  	int cc;
  
+	/* It used the destroy-fast UVC, nothing left to do here */
+	if (!leftover->handle)
+		goto done_fast;
  	cc = uv_cmd_nodata(leftover->handle, UVC_CMD_DESTROY_SEC_CONF, rc, rrc);
  	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY LEFTOVER VM: rc %x rrc %x", *rc, *rrc);
  	WARN_ONCE(cc, "protvirt destroy leftover vm failed rc %x rrc %x", *rc, *rrc);
@@ -215,6 +218,7 @@ static int kvm_s390_pv_dispose_one_leftover(struct kvm *kvm,
  	free_pages(leftover->stor_base, get_order(uv_info.guest_base_stor_len));
  	free_pages(leftover->old_gmap_table, CRST_ALLOC_ORDER);
  	vfree(leftover->stor_var);
+done_fast:
  	atomic_dec(&kvm->mm->context.protected_count);
  	return 0;
  }
@@ -248,6 +252,32 @@ static void kvm_s390_destroy_lower_2g(struct kvm *kvm)
  	srcu_read_unlock(&kvm->srcu, srcu_idx);
  }
  
+static int kvm_s390_pv_deinit_vm_fast(struct kvm *kvm, u16 *rc, u16 *rrc)
+{
+	struct uv_cb_destroy_fast uvcb = {
+		.header.cmd = UVC_CMD_DESTROY_SEC_CONF_FAST,
+		.header.len = sizeof(uvcb),
+		.handle = kvm_s390_pv_get_handle(kvm),
+	};
+	int cc;
+
+	cc = uv_call_sched(0, (u64)&uvcb);
+	*rc = uvcb.header.rc;
+	*rrc = uvcb.header.rrc;
+	WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
+	KVM_UV_EVENT(kvm, 3, "PROTVIRT DESTROY VM FAST: rc %x rrc %x", *rc, *rrc);
+	WARN_ONCE(cc, "protvirt destroy vm fast failed rc %x rrc %x", *rc, *rrc);
+	/* Inteded memory leak on "impossible" error */
+	if (!cc)
+		kvm_s390_pv_dealloc_vm(kvm);
+	return cc ? -EIO : 0;
+}
+
+static inline bool is_destroy_fast_available(void)
+{
+	return test_bit_inv(BIT_UVC_CMD_DESTROY_SEC_CONF_FAST, uv_info.inst_calls_list);
+}
+
  /**
   * kvm_s390_pv_set_aside - Set aside a protected VM for later teardown.
   * @kvm: the VM
@@ -269,6 +299,7 @@ static void kvm_s390_destroy_lower_2g(struct kvm *kvm)
  int kvm_s390_pv_set_aside(struct kvm *kvm, u16 *rc, u16 *rrc)
  {
  	struct pv_vm_to_be_destroyed *priv;
+	int res = 0;
  
  	/*
  	 * If another protected VM was already prepared for teardown, refuse.
@@ -280,14 +311,21 @@ int kvm_s390_pv_set_aside(struct kvm *kvm, u16 *rc, u16 *rrc)
  	if (!priv)
  		return -ENOMEM;
  
-	priv->stor_var = kvm->arch.pv.stor_var;
-	priv->stor_base = kvm->arch.pv.stor_base;
-	priv->handle = kvm_s390_pv_get_handle(kvm);
-	priv->old_gmap_table = (unsigned long)kvm->arch.gmap->table;
-	WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
-	if (s390_replace_asce(kvm->arch.gmap)) {
+	if (is_destroy_fast_available()) {
+		res = kvm_s390_pv_deinit_vm_fast(kvm, rc, rrc);
+	} else {
+		priv->stor_var = kvm->arch.pv.stor_var;
+		priv->stor_base = kvm->arch.pv.stor_base;
+		priv->handle = kvm_s390_pv_get_handle(kvm);
+		priv->old_gmap_table = (unsigned long)kvm->arch.gmap->table;
+		WRITE_ONCE(kvm->arch.gmap->guest_handle, 0);
+		if (s390_replace_asce(kvm->arch.gmap))
+			res = -ENOMEM;
+	}
+
+	if (res) {
  		kfree(priv);
-		return -ENOMEM;
+		return res;
  	}
  
  	kvm_s390_destroy_lower_2g(kvm);
@@ -464,6 +502,7 @@ static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
  {
  	struct kvm *kvm = container_of(subscription, struct kvm, arch.pv.mmu_notifier);
  	u16 dummy;
+	int r;
  
  	/*
  	 * No locking is needed since this is the last thread of the last user of this
@@ -472,7 +511,9 @@ static void kvm_s390_pv_mmu_notifier_release(struct mmu_notifier *subscription,
  	 * unregistered. This means that if this notifier runs, then the
  	 * struct kvm is still valid.
  	 */
-	kvm_s390_cpus_from_pv(kvm, &dummy, &dummy);
+	r = kvm_s390_cpus_from_pv(kvm, &dummy, &dummy);
+	if (!r && is_destroy_fast_available())
+		kvm_s390_pv_deinit_vm_fast(kvm, &dummy, &dummy);
  }
  
  static const struct mmu_notifier_ops kvm_s390_pv_mmu_notifier_ops = {






