KVM: PPC: Book3S HV: Framework and hcall stubs for nested virtualization

This starts the process of adding the code to support nested HV-style
virtualization.  It defines a new H_SET_PARTITION_TABLE hypercall which
a nested hypervisor can use to set the base address and size of a
partition table in its memory (analogous to the PTCR register).
On the host (level 0 hypervisor) side, the H_SET_PARTITION_TABLE
hypercall from the guest is handled by code that saves the virtual
PTCR value for the guest.

This also adds code for creating and destroying nested guests and for
reading the partition table entry for a nested guest from L1 memory.
Each nested guest has its own shadow LPID value, different in general
from the LPID value used by the nested hypervisor to refer to it.  The
shadow LPID value is allocated at nested guest creation time.

Nested hypervisor functionality is only available for a radix guest,
which therefore means a radix host on a POWER9 (or later) processor.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 301 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/book3s_hv_nested.c b/arch/powerpc/kvm/book3s_hv_nested.c
new file mode 100644
index 000000000000..327826248314
--- /dev/null
+++ b/arch/powerpc/kvm/book3s_hv_nested.c
@@ -0,0 +1,301 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright IBM Corporation, 2018
+ * Authors Suraj Jitindar Singh <sjitindarsingh@gmail.com>
+ *	   Paul Mackerras <paulus@ozlabs.org>
+ *
+ * Description: KVM functions specific to running nested KVM-HV guests
+ * on Book3S processors (specifically POWER9 and later).
+ */
+
+#include <linux/kernel.h>
+#include <linux/kvm_host.h>
+
+#include <asm/kvm_ppc.h>
+#include <asm/mmu.h>
+#include <asm/pgtable.h>
+#include <asm/pgalloc.h>
+
+static struct patb_entry *pseries_partition_tb;
+
+static void kvmhv_update_ptbl_cache(struct kvm_nested_guest *gp);
+
+long kvmhv_nested_init(void)
+{
+	long int ptb_order;
+	unsigned long ptcr;
+	long rc;
+
+	if (!kvmhv_on_pseries())
+		return 0;
+	if (!radix_enabled())
+		return -ENODEV;
+
+	/* find log base 2 of KVMPPC_NR_LPIDS, rounding up */
+	ptb_order = __ilog2(KVMPPC_NR_LPIDS - 1) + 1;
+	if (ptb_order < 8)
+		ptb_order = 8;
+	pseries_partition_tb = kmalloc(sizeof(struct patb_entry) << ptb_order,
+				       GFP_KERNEL);
+	if (!pseries_partition_tb) {
+		pr_err("kvm-hv: failed to allocated nested partition table\n");
+		return -ENOMEM;
+	}
+
+	ptcr = __pa(pseries_partition_tb) | (ptb_order - 8);
+	rc = plpar_hcall_norets(H_SET_PARTITION_TABLE, ptcr);
+	if (rc != H_SUCCESS) {
+		pr_err("kvm-hv: Parent hypervisor does not support nesting (rc=%ld)\n",
+		       rc);
+		kfree(pseries_partition_tb);
+		pseries_partition_tb = NULL;
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+void kvmhv_nested_exit(void)
+{
+	/*
+	 * N.B. the kvmhv_on_pseries() test is there because it enables
+	 * the compiler to remove the call to plpar_hcall_norets()
+	 * when CONFIG_PPC_PSERIES=n.
+	 */
+	if (kvmhv_on_pseries() && pseries_partition_tb) {
+		plpar_hcall_norets(H_SET_PARTITION_TABLE, 0);
+		kfree(pseries_partition_tb);
+		pseries_partition_tb = NULL;
+	}
+}
+
+void kvmhv_set_ptbl_entry(unsigned int lpid, u64 dw0, u64 dw1)
+{
+	if (cpu_has_feature(CPU_FTR_HVMODE)) {
+		mmu_partition_table_set_entry(lpid, dw0, dw1);
+	} else {
+		pseries_partition_tb[lpid].patb0 = cpu_to_be64(dw0);
+		pseries_partition_tb[lpid].patb1 = cpu_to_be64(dw1);
+	}
+}
+
+static void kvmhv_set_nested_ptbl(struct kvm_nested_guest *gp)
+{
+	unsigned long dw0;
+
+	dw0 = PATB_HR | radix__get_tree_size() |
+		__pa(gp->shadow_pgtable) | RADIX_PGD_INDEX_SIZE;
+	kvmhv_set_ptbl_entry(gp->shadow_lpid, dw0, gp->process_table);
+}
+
+void kvmhv_vm_nested_init(struct kvm *kvm)
+{
+	kvm->arch.max_nested_lpid = -1;
+}
+
+/*
+ * Handle the H_SET_PARTITION_TABLE hcall.
+ * r4 = guest real address of partition table + log_2(size) - 12
+ * (formatted as for the PTCR).
+ */
+long kvmhv_set_partition_table(struct kvm_vcpu *vcpu)
+{
+	struct kvm *kvm = vcpu->kvm;
+	unsigned long ptcr = kvmppc_get_gpr(vcpu, 4);
+	int srcu_idx;
+	long ret = H_SUCCESS;
+
+	srcu_idx = srcu_read_lock(&kvm->srcu);
+	/*
+	 * Limit the partition table to 4096 entries (because that's what
+	 * hardware supports), and check the base address.
+	 */
+	if ((ptcr & PRTS_MASK) > 12 - 8 ||
+	    !kvm_is_visible_gfn(vcpu->kvm, (ptcr & PRTB_MASK) >> PAGE_SHIFT))
+		ret = H_PARAMETER;
+	srcu_read_unlock(&kvm->srcu, srcu_idx);
+	if (ret == H_SUCCESS)
+		kvm->arch.l1_ptcr = ptcr;
+	return ret;
+}
+
+/*
+ * Reload the partition table entry for a guest.
+ * Caller must hold gp->tlb_lock.
+ */
+static void kvmhv_update_ptbl_cache(struct kvm_nested_guest *gp)
+{
+	int ret;
+	struct patb_entry ptbl_entry;
+	unsigned long ptbl_addr;
+	struct kvm *kvm = gp->l1_host;
+
+	ret = -EFAULT;
+	ptbl_addr = (kvm->arch.l1_ptcr & PRTB_MASK) + (gp->l1_lpid << 4);
+	if (gp->l1_lpid < (1ul << ((kvm->arch.l1_ptcr & PRTS_MASK) + 8)))
+		ret = kvm_read_guest(kvm, ptbl_addr,
+				     &ptbl_entry, sizeof(ptbl_entry));
+	if (ret) {
+		gp->l1_gr_to_hr = 0;
+		gp->process_table = 0;
+	} else {
+		gp->l1_gr_to_hr = be64_to_cpu(ptbl_entry.patb0);
+		gp->process_table = be64_to_cpu(ptbl_entry.patb1);
+	}
+	kvmhv_set_nested_ptbl(gp);
+}
+
+struct kvm_nested_guest *kvmhv_alloc_nested(struct kvm *kvm, unsigned int lpid)
+{
+	struct kvm_nested_guest *gp;
+	long shadow_lpid;
+
+	gp = kzalloc(sizeof(*gp), GFP_KERNEL);
+	if (!gp)
+		return NULL;
+	gp->l1_host = kvm;
+	gp->l1_lpid = lpid;
+	mutex_init(&gp->tlb_lock);
+	gp->shadow_pgtable = pgd_alloc(kvm->mm);
+	if (!gp->shadow_pgtable)
+		goto out_free;
+	shadow_lpid = kvmppc_alloc_lpid();
+	if (shadow_lpid < 0)
+		goto out_free2;
+	gp->shadow_lpid = shadow_lpid;
+
+	return gp;
+
+ out_free2:
+	pgd_free(kvm->mm, gp->shadow_pgtable);
+ out_free:
+	kfree(gp);
+	return NULL;
+}
+
+/*
+ * Free up any resources allocated for a nested guest.
+ */
+static void kvmhv_release_nested(struct kvm_nested_guest *gp)
+{
+	kvmhv_set_ptbl_entry(gp->shadow_lpid, 0, 0);
+	kvmppc_free_lpid(gp->shadow_lpid);
+	if (gp->shadow_pgtable)
+		pgd_free(gp->l1_host->mm, gp->shadow_pgtable);
+	kfree(gp);
+}
+
+static void kvmhv_remove_nested(struct kvm_nested_guest *gp)
+{
+	struct kvm *kvm = gp->l1_host;
+	int lpid = gp->l1_lpid;
+	long ref;
+
+	spin_lock(&kvm->mmu_lock);
+	if (gp == kvm->arch.nested_guests[lpid]) {
+		kvm->arch.nested_guests[lpid] = NULL;
+		if (lpid == kvm->arch.max_nested_lpid) {
+			while (--lpid >= 0 && !kvm->arch.nested_guests[lpid])
+				;
+			kvm->arch.max_nested_lpid = lpid;
+		}
+		--gp->refcnt;
+	}
+	ref = gp->refcnt;
+	spin_unlock(&kvm->mmu_lock);
+	if (ref == 0)
+		kvmhv_release_nested(gp);
+}
+
+/*
+ * Free up all nested resources allocated for this guest.
+ * This is called with no vcpus of the guest running, when
+ * switching the guest to HPT mode or when destroying the
+ * guest.
+ */
+void kvmhv_release_all_nested(struct kvm *kvm)
+{
+	int i;
+	struct kvm_nested_guest *gp;
+	struct kvm_nested_guest *freelist = NULL;
+
+	spin_lock(&kvm->mmu_lock);
+	for (i = 0; i <= kvm->arch.max_nested_lpid; i++) {
+		gp = kvm->arch.nested_guests[i];
+		if (!gp)
+			continue;
+		kvm->arch.nested_guests[i] = NULL;
+		if (--gp->refcnt == 0) {
+			gp->next = freelist;
+			freelist = gp;
+		}
+	}
+	kvm->arch.max_nested_lpid = -1;
+	spin_unlock(&kvm->mmu_lock);
+	while ((gp = freelist) != NULL) {
+		freelist = gp->next;
+		kvmhv_release_nested(gp);
+	}
+}
+
+/* caller must hold gp->tlb_lock */
+void kvmhv_flush_nested(struct kvm_nested_guest *gp)
+{
+	kvmhv_update_ptbl_cache(gp);
+	if (gp->l1_gr_to_hr == 0)
+		kvmhv_remove_nested(gp);
+}
+
+struct kvm_nested_guest *kvmhv_get_nested(struct kvm *kvm, int l1_lpid,
+					  bool create)
+{
+	struct kvm_nested_guest *gp, *newgp;
+
+	if (l1_lpid >= KVM_MAX_NESTED_GUESTS ||
+	    l1_lpid >= (1ul << ((kvm->arch.l1_ptcr & PRTS_MASK) + 12 - 4)))
+		return NULL;
+
+	spin_lock(&kvm->mmu_lock);
+	gp = kvm->arch.nested_guests[l1_lpid];
+	if (gp)
+		++gp->refcnt;
+	spin_unlock(&kvm->mmu_lock);
+
+	if (gp || !create)
+		return gp;
+
+	newgp = kvmhv_alloc_nested(kvm, l1_lpid);
+	if (!newgp)
+		return NULL;
+	spin_lock(&kvm->mmu_lock);
+	if (kvm->arch.nested_guests[l1_lpid]) {
+		/* someone else beat us to it */
+		gp = kvm->arch.nested_guests[l1_lpid];
+	} else {
+		kvm->arch.nested_guests[l1_lpid] = newgp;
+		++newgp->refcnt;
+		gp = newgp;
+		newgp = NULL;
+		if (l1_lpid > kvm->arch.max_nested_lpid)
+			kvm->arch.max_nested_lpid = l1_lpid;
+	}
+	++gp->refcnt;
+	spin_unlock(&kvm->mmu_lock);
+
+	if (newgp)
+		kvmhv_release_nested(newgp);
+
+	return gp;
+}
+
+void kvmhv_put_nested(struct kvm_nested_guest *gp)
+{
+	struct kvm *kvm = gp->l1_host;
+	long ref;
+
+	spin_lock(&kvm->mmu_lock);
+	ref = --gp->refcnt;
+	spin_unlock(&kvm->mmu_lock);
+	if (ref == 0)
+		kvmhv_release_nested(gp);
+}