arch/powerpc/kvm/book3s_hv_nested.c

// 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);
}