// SPDX-License-Identifier: GPL-2.0-only
/*
 * Support for the hypercall interface exposed to protected guests by
 * pKVM.
 *
 * Author: Will Deacon <will@kernel.org>
 * Copyright (C) 2024 Google LLC
 */

#include <linux/arm-smccc.h>
#include <linux/array_size.h>
#include <linux/io.h>
#include <linux/mem_encrypt.h>
#include <linux/mm.h>
#include <linux/pgtable.h>

#include <asm/hypervisor.h>

static size_t pkvm_granule;

static int arm_smccc_do_one_page(u32 func_id, phys_addr_t phys)
{
        phys_addr_t end = phys + PAGE_SIZE;

        while (phys < end) {
                struct arm_smccc_res res;

                arm_smccc_1_1_invoke(func_id, phys, 0, 0, &res);
                if (res.a0 != SMCCC_RET_SUCCESS)
                        return -EPERM;

                phys += pkvm_granule;
        }

        return 0;
}

static int __set_memory_range(u32 func_id, unsigned long start, int numpages)
{
        void *addr = (void *)start, *end = addr + numpages * PAGE_SIZE;

        while (addr < end) {
                int err;

                err = arm_smccc_do_one_page(func_id, virt_to_phys(addr));
                if (err)
                        return err;

                addr += PAGE_SIZE;
        }

        return 0;
}

static int pkvm_set_memory_encrypted(unsigned long addr, int numpages)
{
        return __set_memory_range(ARM_SMCCC_VENDOR_HYP_KVM_MEM_UNSHARE_FUNC_ID,
                                  addr, numpages);
}

static int pkvm_set_memory_decrypted(unsigned long addr, int numpages)
{
        return __set_memory_range(ARM_SMCCC_VENDOR_HYP_KVM_MEM_SHARE_FUNC_ID,
                                  addr, numpages);
}

static const struct arm64_mem_crypt_ops pkvm_crypt_ops = {
        .encrypt        = pkvm_set_memory_encrypted,
        .decrypt        = pkvm_set_memory_decrypted,
};

static int mmio_guard_ioremap_hook(phys_addr_t phys, size_t size,
                                   pgprot_t *prot)
{
        phys_addr_t end;
        pteval_t protval = pgprot_val(*prot);

        /*
         * We only expect MMIO emulation for regions mapped with device
         * attributes.
         */
        if (protval != PROT_DEVICE_nGnRE && protval != PROT_DEVICE_nGnRnE)
                return 0;

        phys = PAGE_ALIGN_DOWN(phys);
        end = phys + PAGE_ALIGN(size);

        while (phys < end) {
                const int func_id = ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_FUNC_ID;

                WARN_ON_ONCE(arm_smccc_do_one_page(func_id, phys));
                phys += PAGE_SIZE;
        }

        return 0;
}

void pkvm_init_hyp_services(void)
{
        int i;
        struct arm_smccc_res res;
        const u32 funcs[] = {
                ARM_SMCCC_KVM_FUNC_HYP_MEMINFO,
                ARM_SMCCC_KVM_FUNC_MEM_SHARE,
                ARM_SMCCC_KVM_FUNC_MEM_UNSHARE,
        };

        for (i = 0; i < ARRAY_SIZE(funcs); ++i) {
                if (!kvm_arm_hyp_service_available(funcs[i]))
                        return;
        }

        arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_HYP_MEMINFO_FUNC_ID,
                             0, 0, 0, &res);
        if (res.a0 > PAGE_SIZE) /* Includes error codes */
                return;

        pkvm_granule = res.a0;
        arm64_mem_crypt_ops_register(&pkvm_crypt_ops);

        if (kvm_arm_hyp_service_available(ARM_SMCCC_KVM_FUNC_MMIO_GUARD))
                arm64_ioremap_prot_hook_register(&mmio_guard_ioremap_hook);
}