nacl.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2024 Ventana Micro Systems Inc.
 */

#include <linux/kvm_host.h>
#include <linux/vmalloc.h>
#include <asm/kvm_nacl.h>

DEFINE_STATIC_KEY_FALSE(kvm_riscv_nacl_available);
DEFINE_STATIC_KEY_FALSE(kvm_riscv_nacl_sync_csr_available);
DEFINE_STATIC_KEY_FALSE(kvm_riscv_nacl_sync_hfence_available);
DEFINE_STATIC_KEY_FALSE(kvm_riscv_nacl_sync_sret_available);
DEFINE_STATIC_KEY_FALSE(kvm_riscv_nacl_autoswap_csr_available);
DEFINE_PER_CPU(struct kvm_riscv_nacl, kvm_riscv_nacl);

void __kvm_riscv_nacl_hfence(void *shmem,
			     unsigned long control,
			     unsigned long page_num,
			     unsigned long page_count)
{
	int i, ent = -1, try_count = 5;
	unsigned long *entp;

again:
	for (i = 0; i < SBI_NACL_SHMEM_HFENCE_ENTRY_MAX; i++) {
		entp = shmem + SBI_NACL_SHMEM_HFENCE_ENTRY_CONFIG(i);
		if (lelong_to_cpu(*entp) & SBI_NACL_SHMEM_HFENCE_CONFIG_PEND)
			continue;

		ent = i;
		break;
	}

	if (ent < 0) {
		if (try_count) {
			nacl_sync_hfence(-1UL);
			goto again;
		} else {
			pr_warn("KVM: No free entry in NACL shared memory\n");
			return;
		}
	}

	entp = shmem + SBI_NACL_SHMEM_HFENCE_ENTRY_CONFIG(i);
	*entp = cpu_to_lelong(control);
	entp = shmem + SBI_NACL_SHMEM_HFENCE_ENTRY_PNUM(i);
	*entp = cpu_to_lelong(page_num);
	entp = shmem + SBI_NACL_SHMEM_HFENCE_ENTRY_PCOUNT(i);
	*entp = cpu_to_lelong(page_count);
}

int kvm_riscv_nacl_enable(void)
{
	int rc;
	struct sbiret ret;
	struct kvm_riscv_nacl *nacl;

	if (!kvm_riscv_nacl_available())
		return 0;
	nacl = this_cpu_ptr(&kvm_riscv_nacl);

	ret = sbi_ecall(SBI_EXT_NACL, SBI_EXT_NACL_SET_SHMEM,
			nacl->shmem_phys, 0, 0, 0, 0, 0);
	rc = sbi_err_map_linux_errno(ret.error);
	if (rc)
		return rc;

	return 0;
}

void kvm_riscv_nacl_disable(void)
{
	if (!kvm_riscv_nacl_available())
		return;

	sbi_ecall(SBI_EXT_NACL, SBI_EXT_NACL_SET_SHMEM,
		  SBI_SHMEM_DISABLE, SBI_SHMEM_DISABLE, 0, 0, 0, 0);
}

void kvm_riscv_nacl_exit(void)
{
	int cpu;
	struct kvm_riscv_nacl *nacl;

	if (!kvm_riscv_nacl_available())
		return;

	/* Allocate per-CPU shared memory */
	for_each_possible_cpu(cpu) {
		nacl = per_cpu_ptr(&kvm_riscv_nacl, cpu);
		if (!nacl->shmem)
			continue;

		free_pages((unsigned long)nacl->shmem,
			   get_order(SBI_NACL_SHMEM_SIZE));
		nacl->shmem = NULL;
		nacl->shmem_phys = 0;
	}
}

static long nacl_probe_feature(long feature_id)
{
	struct sbiret ret;

	if (!kvm_riscv_nacl_available())
		return 0;

	ret = sbi_ecall(SBI_EXT_NACL, SBI_EXT_NACL_PROBE_FEATURE,
			feature_id, 0, 0, 0, 0, 0);
	return ret.value;
}

int kvm_riscv_nacl_init(void)
{
	int cpu;
	struct page *shmem_page;
	struct kvm_riscv_nacl *nacl;

	if (sbi_spec_version < sbi_mk_version(1, 0) ||
	    sbi_probe_extension(SBI_EXT_NACL) <= 0)
		return -ENODEV;

	/* Enable NACL support */
	static_branch_enable(&kvm_riscv_nacl_available);

	/* Probe NACL features */
	if (nacl_probe_feature(SBI_NACL_FEAT_SYNC_CSR))
		static_branch_enable(&kvm_riscv_nacl_sync_csr_available);
	if (nacl_probe_feature(SBI_NACL_FEAT_SYNC_HFENCE))
		static_branch_enable(&kvm_riscv_nacl_sync_hfence_available);
	if (nacl_probe_feature(SBI_NACL_FEAT_SYNC_SRET))
		static_branch_enable(&kvm_riscv_nacl_sync_sret_available);
	if (nacl_probe_feature(SBI_NACL_FEAT_AUTOSWAP_CSR))
		static_branch_enable(&kvm_riscv_nacl_autoswap_csr_available);

	/* Allocate per-CPU shared memory */
	for_each_possible_cpu(cpu) {
		nacl = per_cpu_ptr(&kvm_riscv_nacl, cpu);

		shmem_page = alloc_pages(GFP_KERNEL | __GFP_ZERO,
					 get_order(SBI_NACL_SHMEM_SIZE));
		if (!shmem_page) {
			kvm_riscv_nacl_exit();
			return -ENOMEM;
		}
		nacl->shmem = page_to_virt(shmem_page);
		nacl->shmem_phys = page_to_phys(shmem_page);
	}

	return 0;
}