arm-pkvm-guest.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Support for the hypercall interface exposed to protected guests by
  4 * pKVM.
  5 *
  6 * Author: Will Deacon <will@kernel.org>
  7 * Copyright (C) 2024 Google LLC
  8 */
  9
 10#include <linux/arm-smccc.h>
 11#include <linux/array_size.h>
 12#include <linux/io.h>
 13#include <linux/mem_encrypt.h>
 14#include <linux/mm.h>
 15#include <linux/pgtable.h>
 16
 17#include <asm/hypervisor.h>
 18
 19static size_t pkvm_granule;
 20
 21static int arm_smccc_do_one_page(u32 func_id, phys_addr_t phys)
 22{
 23	phys_addr_t end = phys + PAGE_SIZE;
 24
 25	while (phys < end) {
 26		struct arm_smccc_res res;
 27
 28		arm_smccc_1_1_invoke(func_id, phys, 0, 0, &res);
 29		if (res.a0 != SMCCC_RET_SUCCESS)
 30			return -EPERM;
 31
 32		phys += pkvm_granule;
 33	}
 34
 35	return 0;
 36}
 37
 38static int __set_memory_range(u32 func_id, unsigned long start, int numpages)
 39{
 40	void *addr = (void *)start, *end = addr + numpages * PAGE_SIZE;
 41
 42	while (addr < end) {
 43		int err;
 44
 45		err = arm_smccc_do_one_page(func_id, virt_to_phys(addr));
 46		if (err)
 47			return err;
 48
 49		addr += PAGE_SIZE;
 50	}
 51
 52	return 0;
 53}
 54
 55static int pkvm_set_memory_encrypted(unsigned long addr, int numpages)
 56{
 57	return __set_memory_range(ARM_SMCCC_VENDOR_HYP_KVM_MEM_UNSHARE_FUNC_ID,
 58				  addr, numpages);
 59}
 60
 61static int pkvm_set_memory_decrypted(unsigned long addr, int numpages)
 62{
 63	return __set_memory_range(ARM_SMCCC_VENDOR_HYP_KVM_MEM_SHARE_FUNC_ID,
 64				  addr, numpages);
 65}
 66
 67static const struct arm64_mem_crypt_ops pkvm_crypt_ops = {
 68	.encrypt	= pkvm_set_memory_encrypted,
 69	.decrypt	= pkvm_set_memory_decrypted,
 70};
 71
 72static int mmio_guard_ioremap_hook(phys_addr_t phys, size_t size,
 73				   pgprot_t *prot)
 74{
 75	phys_addr_t end;
 76	pteval_t protval = pgprot_val(*prot);
 77
 78	/*
 79	 * We only expect MMIO emulation for regions mapped with device
 80	 * attributes.
 81	 */
 82	if (protval != PROT_DEVICE_nGnRE && protval != PROT_DEVICE_nGnRnE)
 83		return 0;
 84
 85	phys = PAGE_ALIGN_DOWN(phys);
 86	end = phys + PAGE_ALIGN(size);
 87
 88	while (phys < end) {
 89		const int func_id = ARM_SMCCC_VENDOR_HYP_KVM_MMIO_GUARD_FUNC_ID;
 90
 91		WARN_ON_ONCE(arm_smccc_do_one_page(func_id, phys));
 92		phys += PAGE_SIZE;
 93	}
 94
 95	return 0;
 96}
 97
 98void pkvm_init_hyp_services(void)
 99{
100	int i;
101	struct arm_smccc_res res;
102	const u32 funcs[] = {
103		ARM_SMCCC_KVM_FUNC_HYP_MEMINFO,
104		ARM_SMCCC_KVM_FUNC_MEM_SHARE,
105		ARM_SMCCC_KVM_FUNC_MEM_UNSHARE,
106	};
107
108	for (i = 0; i < ARRAY_SIZE(funcs); ++i) {
109		if (!kvm_arm_hyp_service_available(funcs[i]))
110			return;
111	}
112
113	arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_HYP_MEMINFO_FUNC_ID,
114			     0, 0, 0, &res);
115	if (res.a0 > PAGE_SIZE) /* Includes error codes */
116		return;
117
118	pkvm_granule = res.a0;
119	arm64_mem_crypt_ops_register(&pkvm_crypt_ops);
120
121	if (kvm_arm_hyp_service_available(ARM_SMCCC_KVM_FUNC_MMIO_GUARD))
122		arm64_ioremap_prot_hook_register(&mmio_guard_ioremap_hook);
123}