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// SPDX-License-Identifier: GPL-2.0
/*
* VMID allocator.
*
* Based on Arm64 ASID allocator algorithm.
* Please refer arch/arm64/mm/context.c for detailed
* comments on algorithm.
*
* Copyright (C) 2002-2003 Deep Blue Solutions Ltd, all rights reserved.
* Copyright (C) 2012 ARM Ltd.
*/
#include <linux/bitfield.h>
#include <linux/bitops.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_mmu.h>
unsigned int __ro_after_init kvm_arm_vmid_bits;
static DEFINE_RAW_SPINLOCK(cpu_vmid_lock);
static atomic64_t vmid_generation;
static unsigned long *vmid_map;
static DEFINE_PER_CPU(atomic64_t, active_vmids);
static DEFINE_PER_CPU(u64, reserved_vmids);
#define VMID_MASK (~GENMASK(kvm_arm_vmid_bits - 1, 0))
#define VMID_FIRST_VERSION (1UL << kvm_arm_vmid_bits)
#define NUM_USER_VMIDS VMID_FIRST_VERSION
#define vmid2idx(vmid) ((vmid) & ~VMID_MASK)
#define idx2vmid(idx) vmid2idx(idx)
/*
* As vmid #0 is always reserved, we will never allocate one
* as below and can be treated as invalid. This is used to
* set the active_vmids on vCPU schedule out.
*/
#define VMID_ACTIVE_INVALID VMID_FIRST_VERSION
#define vmid_gen_match(vmid) \
(!(((vmid) ^ atomic64_read(&vmid_generation)) >> kvm_arm_vmid_bits))
static void flush_context(void)
{
int cpu;
u64 vmid;
bitmap_zero(vmid_map, NUM_USER_VMIDS);
for_each_possible_cpu(cpu) {
vmid = atomic64_xchg_relaxed(&per_cpu(active_vmids, cpu), 0);
/* Preserve reserved VMID */
if (vmid == 0)
vmid = per_cpu(reserved_vmids, cpu);
__set_bit(vmid2idx(vmid), vmid_map);
per_cpu(reserved_vmids, cpu) = vmid;
}
/*
* Unlike ASID allocator, we expect less frequent rollover in
* case of VMIDs. Hence, instead of marking the CPU as
* flush_pending and issuing a local context invalidation on
* the next context-switch, we broadcast TLB flush + I-cache
* invalidation over the inner shareable domain on rollover.
*/
kvm_call_hyp(__kvm_flush_vm_context);
}
static bool check_update_reserved_vmid(u64 vmid, u64 newvmid)
{
int cpu;
bool hit = false;
/*
* Iterate over the set of reserved VMIDs looking for a match
* and update to use newvmid (i.e. the same VMID in the current
* generation).
*/
for_each_possible_cpu(cpu) {
if (per_cpu(reserved_vmids, cpu) == vmid) {
hit = true;
per_cpu(reserved_vmids, cpu) = newvmid;
}
}
return hit;
}
static u64 new_vmid(struct kvm_vmid *kvm_vmid)
{
static u32 cur_idx = 1;
u64 vmid = atomic64_read(&kvm_vmid->id);
u64 generation = atomic64_read(&vmid_generation);
if (vmid != 0) {
u64 newvmid = generation | (vmid & ~VMID_MASK);
if (check_update_reserved_vmid(vmid, newvmid)) {
atomic64_set(&kvm_vmid->id, newvmid);
return newvmid;
}
if (!__test_and_set_bit(vmid2idx(vmid), vmid_map)) {
atomic64_set(&kvm_vmid->id, newvmid);
return newvmid;
}
}
vmid = find_next_zero_bit(vmid_map, NUM_USER_VMIDS, cur_idx);
if (vmid != NUM_USER_VMIDS)
goto set_vmid;
/* We're out of VMIDs, so increment the global generation count */
generation = atomic64_add_return_relaxed(VMID_FIRST_VERSION,
&vmid_generation);
flush_context();
/* We have more VMIDs than CPUs, so this will always succeed */
vmid = find_next_zero_bit(vmid_map, NUM_USER_VMIDS, 1);
set_vmid:
__set_bit(vmid, vmid_map);
cur_idx = vmid;
vmid = idx2vmid(vmid) | generation;
atomic64_set(&kvm_vmid->id, vmid);
return vmid;
}
/* Called from vCPU sched out with preemption disabled */
void kvm_arm_vmid_clear_active(void)
{
atomic64_set(this_cpu_ptr(&active_vmids), VMID_ACTIVE_INVALID);
}
bool kvm_arm_vmid_update(struct kvm_vmid *kvm_vmid)
{
unsigned long flags;
u64 vmid, old_active_vmid;
bool updated = false;
vmid = atomic64_read(&kvm_vmid->id);
/*
* Please refer comments in check_and_switch_context() in
* arch/arm64/mm/context.c.
*
* Unlike ASID allocator, we set the active_vmids to
* VMID_ACTIVE_INVALID on vCPU schedule out to avoid
* reserving the VMID space needlessly on rollover.
* Hence explicitly check here for a "!= 0" to
* handle the sync with a concurrent rollover.
*/
old_active_vmid = atomic64_read(this_cpu_ptr(&active_vmids));
if (old_active_vmid != 0 && vmid_gen_match(vmid) &&
0 != atomic64_cmpxchg_relaxed(this_cpu_ptr(&active_vmids),
old_active_vmid, vmid))
return false;
raw_spin_lock_irqsave(&cpu_vmid_lock, flags);
/* Check that our VMID belongs to the current generation. */
vmid = atomic64_read(&kvm_vmid->id);
if (!vmid_gen_match(vmid)) {
vmid = new_vmid(kvm_vmid);
updated = true;
}
atomic64_set(this_cpu_ptr(&active_vmids), vmid);
raw_spin_unlock_irqrestore(&cpu_vmid_lock, flags);
return updated;
}
/*
* Initialize the VMID allocator
*/
int __init kvm_arm_vmid_alloc_init(void)
{
kvm_arm_vmid_bits = kvm_get_vmid_bits();
/*
* Expect allocation after rollover to fail if we don't have
* at least one more VMID than CPUs. VMID #0 is always reserved.
*/
WARN_ON(NUM_USER_VMIDS - 1 <= num_possible_cpus());
atomic64_set(&vmid_generation, VMID_FIRST_VERSION);
vmid_map = bitmap_zalloc(NUM_USER_VMIDS, GFP_KERNEL);
if (!vmid_map)
return -ENOMEM;
return 0;
}
void __init kvm_arm_vmid_alloc_free(void)
{
bitmap_free(vmid_map);
}
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