mm.c

Go to the documentation of this file.

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2020 Google LLC
 * Author: Quentin Perret <qperret@google.com>
 */
 
#include <linux/kvm_host.h>
#include <asm/kvm_hyp.h>
#include <asm/kvm_mmu.h>
#include <asm/kvm_pgtable.h>
#include <asm/kvm_pkvm.h>
#include <asm/spectre.h>
 
#include <nvhe/early_alloc.h>
#include <nvhe/gfp.h>
#include <nvhe/memory.h>
#include <nvhe/mem_protect.h>
#include <nvhe/mm.h>
#include <nvhe/spinlock.h>
 
struct kvm_pgtable pkvm_pgtable;
hyp_spinlock_t pkvm_pgd_lock;
 
struct memblock_region hyp_memory[HYP_MEMBLOCK_REGIONS];
unsigned int hyp_memblock_nr;
 
static u64 __io_map_base;
 
struct hyp_fixmap_slot {
    u64 addr;
    kvm_pte_t *ptep;
};
static DEFINE_PER_CPU(struct hyp_fixmap_slot, fixmap_slots);
 
static int __pkvm_create_mappings(unsigned long start, unsigned long size,
                  unsigned long phys, enum kvm_pgtable_prot prot)
{
    int err;
 
    hyp_spin_lock(&pkvm_pgd_lock);
    err = kvm_pgtable_hyp_map(&pkvm_pgtable, start, size, phys, prot);
    hyp_spin_unlock(&pkvm_pgd_lock);
 
    return err;
}
 
static int __pkvm_alloc_private_va_range(unsigned long start, size_t size)
{
    unsigned long cur;
 
    hyp_assert_lock_held(&pkvm_pgd_lock);
 
    if (!start || start < __io_map_base)
        return -EINVAL;
 
    /* The allocated size is always a multiple of PAGE_SIZE */
    cur = start + PAGE_ALIGN(size);
 
    /* Are we overflowing on the vmemmap ? */
    if (cur > __hyp_vmemmap)
        return -ENOMEM;
 
    __io_map_base = cur;
 
    return 0;
}
 
/**
 * pkvm_alloc_private_va_range - Allocates a private VA range.
 * @size:   The size of the VA range to reserve.
 * @haddr:  The hypervisor virtual start address of the allocation.
 *
 * The private virtual address (VA) range is allocated above __io_map_base
 * and aligned based on the order of @size.
 *
 * Return: 0 on success or negative error code on failure.
 */
int pkvm_alloc_private_va_range(size_t size, unsigned long *haddr)
{
    unsigned long addr;
    int ret;
 
    hyp_spin_lock(&pkvm_pgd_lock);
    addr = __io_map_base;
    ret = __pkvm_alloc_private_va_range(addr, size);
    hyp_spin_unlock(&pkvm_pgd_lock);
 
    *haddr = addr;
 
    return ret;
}
 
int __pkvm_create_private_mapping(phys_addr_t phys, size_t size,
                  enum kvm_pgtable_prot prot,
                  unsigned long *haddr)
{
    unsigned long addr;
    int err;
 
    size = PAGE_ALIGN(size + offset_in_page(phys));
    err = pkvm_alloc_private_va_range(size, &addr);
    if (err)
        return err;
 
    err = __pkvm_create_mappings(addr, size, phys, prot);
    if (err)
        return err;
 
    *haddr = addr + offset_in_page(phys);
    return err;
}
 
int pkvm_create_mappings_locked(void *from, void *to, enum kvm_pgtable_prot prot)
{
    unsigned long start = (unsigned long)from;
    unsigned long end = (unsigned long)to;
    unsigned long virt_addr;
    phys_addr_t phys;
 
    hyp_assert_lock_held(&pkvm_pgd_lock);
 
    start = start & PAGE_MASK;
    end = PAGE_ALIGN(end);
 
    for (virt_addr = start; virt_addr < end; virt_addr += PAGE_SIZE) {
        int err;
 
        phys = hyp_virt_to_phys((void *)virt_addr);
        err = kvm_pgtable_hyp_map(&pkvm_pgtable, virt_addr, PAGE_SIZE,
                      phys, prot);
        if (err)
            return err;
    }
 
    return 0;
}
 
int pkvm_create_mappings(void *from, void *to, enum kvm_pgtable_prot prot)
{
    int ret;
 
    hyp_spin_lock(&pkvm_pgd_lock);
    ret = pkvm_create_mappings_locked(from, to, prot);
    hyp_spin_unlock(&pkvm_pgd_lock);
 
    return ret;
}
 
int hyp_back_vmemmap(phys_addr_t back)
{
    unsigned long i, start, size, end = 0;
    int ret;
 
    for (i = 0; i < hyp_memblock_nr; i++) {
        start = hyp_memory[i].base;
        start = ALIGN_DOWN((u64)hyp_phys_to_page(start), PAGE_SIZE);
        /*
         * The begining of the hyp_vmemmap region for the current
         * memblock may already be backed by the page backing the end
         * the previous region, so avoid mapping it twice.
         */
        start = max(start, end);
 
        end = hyp_memory[i].base + hyp_memory[i].size;
        end = PAGE_ALIGN((u64)hyp_phys_to_page(end));
        if (start >= end)
            continue;
 
        size = end - start;
        ret = __pkvm_create_mappings(start, size, back, PAGE_HYP);
        if (ret)
            return ret;
 
        memset(hyp_phys_to_virt(back), 0, size);
        back += size;
    }
 
    return 0;
}
 
static void *__hyp_bp_vect_base;
int pkvm_cpu_set_vector(enum arm64_hyp_spectre_vector slot)
{
    void *vector;
 
    switch (slot) {
    case HYP_VECTOR_DIRECT: {
        vector = __kvm_hyp_vector;
        break;
    }
    case HYP_VECTOR_SPECTRE_DIRECT: {
        vector = __bp_harden_hyp_vecs;
        break;
    }
    case HYP_VECTOR_INDIRECT:
    case HYP_VECTOR_SPECTRE_INDIRECT: {
        vector = (void *)__hyp_bp_vect_base;
        break;
    }
    default:
        return -EINVAL;
    }
 
    vector = __kvm_vector_slot2addr(vector, slot);
    *this_cpu_ptr(&kvm_hyp_vector) = (unsigned long)vector;
 
    return 0;
}
 
int hyp_map_vectors(void)
{
    phys_addr_t phys;
    unsigned long bp_base;
    int ret;
 
    if (!kvm_system_needs_idmapped_vectors()) {
        __hyp_bp_vect_base = __bp_harden_hyp_vecs;
        return 0;
    }
 
    phys = __hyp_pa(__bp_harden_hyp_vecs);
    ret = __pkvm_create_private_mapping(phys, __BP_HARDEN_HYP_VECS_SZ,
                        PAGE_HYP_EXEC, &bp_base);
    if (ret)
        return ret;
 
    __hyp_bp_vect_base = (void *)bp_base;
 
    return 0;
}
 
void *hyp_fixmap_map(phys_addr_t phys)
{
    struct hyp_fixmap_slot *slot = this_cpu_ptr(&fixmap_slots);
    kvm_pte_t pte, *ptep = slot->ptep;
 
    pte = *ptep;
    pte &= ~kvm_phys_to_pte(KVM_PHYS_INVALID);
    pte |= kvm_phys_to_pte(phys) | KVM_PTE_VALID;
    WRITE_ONCE(*ptep, pte);
    dsb(ishst);
 
    return (void *)slot->addr;
}
 
static void fixmap_clear_slot(struct hyp_fixmap_slot *slot)
{
    kvm_pte_t *ptep = slot->ptep;
    u64 addr = slot->addr;
 
    WRITE_ONCE(*ptep, *ptep & ~KVM_PTE_VALID);
 
    /*
     * Irritatingly, the architecture requires that we use inner-shareable
     * broadcast TLB invalidation here in case another CPU speculates
     * through our fixmap and decides to create an "amalagamation of the
     * values held in the TLB" due to the apparent lack of a
     * break-before-make sequence.
     *
     * https://lore.kernel.org/kvm/20221017115209.2099-1-will@kernel.org/T/#mf10dfbaf1eaef9274c581b81c53758918c1d0f03
     */
    dsb(ishst);
    __tlbi_level(vale2is, __TLBI_VADDR(addr, 0), KVM_PGTABLE_LAST_LEVEL);
    dsb(ish);
    isb();
}
 
void hyp_fixmap_unmap(void)
{
    fixmap_clear_slot(this_cpu_ptr(&fixmap_slots));
}
 
static int __create_fixmap_slot_cb(const struct kvm_pgtable_visit_ctx *ctx,
                   enum kvm_pgtable_walk_flags visit)
{
    struct hyp_fixmap_slot *slot = per_cpu_ptr(&fixmap_slots, (u64)ctx->arg);
 
    if (!kvm_pte_valid(ctx->old) || ctx->level != KVM_PGTABLE_LAST_LEVEL)
        return -EINVAL;
 
    slot->addr = ctx->addr;
    slot->ptep = ctx->ptep;
 
    /*
     * Clear the PTE, but keep the page-table page refcount elevated to
     * prevent it from ever being freed. This lets us manipulate the PTEs
     * by hand safely without ever needing to allocate memory.
     */
    fixmap_clear_slot(slot);
 
    return 0;
}
 
static int create_fixmap_slot(u64 addr, u64 cpu)
{
    struct kvm_pgtable_walker walker = {
        .cb = __create_fixmap_slot_cb,
        .flags  = KVM_PGTABLE_WALK_LEAF,
        .arg = (void *)cpu,
    };
 
    return kvm_pgtable_walk(&pkvm_pgtable, addr, PAGE_SIZE, &walker);
}
 
int hyp_create_pcpu_fixmap(void)
{
    unsigned long addr, i;
    int ret;
 
    for (i = 0; i < hyp_nr_cpus; i++) {
        ret = pkvm_alloc_private_va_range(PAGE_SIZE, &addr);
        if (ret)
            return ret;
 
        ret = kvm_pgtable_hyp_map(&pkvm_pgtable, addr, PAGE_SIZE,
                      __hyp_pa(__hyp_bss_start), PAGE_HYP);
        if (ret)
            return ret;
 
        ret = create_fixmap_slot(addr, i);
        if (ret)
            return ret;
    }
 
    return 0;
}
 
int hyp_create_idmap(u32 hyp_va_bits)
{
    unsigned long start, end;
 
    start = hyp_virt_to_phys((void *)__hyp_idmap_text_start);
    start = ALIGN_DOWN(start, PAGE_SIZE);
 
    end = hyp_virt_to_phys((void *)__hyp_idmap_text_end);
    end = ALIGN(end, PAGE_SIZE);
 
    /*
     * One half of the VA space is reserved to linearly map portions of
     * memory -- see va_layout.c for more details. The other half of the VA
     * space contains the trampoline page, and needs some care. Split that
     * second half in two and find the quarter of VA space not conflicting
     * with the idmap to place the IOs and the vmemmap. IOs use the lower
     * half of the quarter and the vmemmap the upper half.
     */
    __io_map_base = start & BIT(hyp_va_bits - 2);
    __io_map_base ^= BIT(hyp_va_bits - 2);
    __hyp_vmemmap = __io_map_base | BIT(hyp_va_bits - 3);
 
    return __pkvm_create_mappings(start, end - start, start, PAGE_HYP_EXEC);
}
 
int pkvm_create_stack(phys_addr_t phys, unsigned long *haddr)
{
    unsigned long addr, prev_base;
    size_t size;
    int ret;
 
    hyp_spin_lock(&pkvm_pgd_lock);
 
    prev_base = __io_map_base;
    /*
     * Efficient stack verification using the PAGE_SHIFT bit implies
     * an alignment of our allocation on the order of the size.
     */
    size = PAGE_SIZE * 2;
    addr = ALIGN(__io_map_base, size);
 
    ret = __pkvm_alloc_private_va_range(addr, size);
    if (!ret) {
        /*
         * Since the stack grows downwards, map the stack to the page
         * at the higher address and leave the lower guard page
         * unbacked.
         *
         * Any valid stack address now has the PAGE_SHIFT bit as 1
         * and addresses corresponding to the guard page have the
         * PAGE_SHIFT bit as 0 - this is used for overflow detection.
         */
        ret = kvm_pgtable_hyp_map(&pkvm_pgtable, addr + PAGE_SIZE,
                      PAGE_SIZE, phys, PAGE_HYP);
        if (ret)
            __io_map_base = prev_base;
    }
    hyp_spin_unlock(&pkvm_pgd_lock);
 
    *haddr = addr + size;
 
    return ret;
}
 
static void *admit_host_page(void *arg)
{
    struct kvm_hyp_memcache *host_mc = arg;
 
    if (!host_mc->nr_pages)
        return NULL;
 
    /*
     * The host still owns the pages in its memcache, so we need to go
     * through a full host-to-hyp donation cycle to change it. Fortunately,
     * __pkvm_host_donate_hyp() takes care of races for us, so if it
     * succeeds we're good to go.
     */
    if (__pkvm_host_donate_hyp(hyp_phys_to_pfn(host_mc->head), 1))
        return NULL;
 
    return pop_hyp_memcache(host_mc, hyp_phys_to_virt);
}
 
/* Refill our local memcache by poping pages from the one provided by the host. */
int refill_memcache(struct kvm_hyp_memcache *mc, unsigned long min_pages,
            struct kvm_hyp_memcache *host_mc)
{
    struct kvm_hyp_memcache tmp = *host_mc;
    int ret;
 
    ret =  __topup_hyp_memcache(mc, min_pages, admit_host_page,
                    hyp_virt_to_phys, &tmp);
    *host_mc = tmp;
 
    return ret;
}