path: root/arch/x86/kernel/sev-shared.c

// SPDX-License-Identifier: GPL-2.0
/*
 * AMD Encrypted Register State Support
 *
 * Author: Joerg Roedel <jroedel@suse.de>
 *
 * This file is not compiled stand-alone. It contains code shared
 * between the pre-decompression boot code and the running Linux kernel
 * and is included directly into both code-bases.
 */

#ifndef __BOOT_COMPRESSED
#define error(v)	pr_err(v)
#define has_cpuflag(f)	boot_cpu_has(f)
#else
#undef WARN
#define WARN(condition, format...) (!!(condition))
#endif

/* I/O parameters for CPUID-related helpers */
struct cpuid_leaf {
	u32 fn;
	u32 subfn;
	u32 eax;
	u32 ebx;
	u32 ecx;
	u32 edx;
};

/*
 * Individual entries of the SNP CPUID table, as defined by the SNP
 * Firmware ABI, Revision 0.9, Section 7.1, Table 14.
 */
struct snp_cpuid_fn {
	u32 eax_in;
	u32 ecx_in;
	u64 xcr0_in;
	u64 xss_in;
	u32 eax;
	u32 ebx;
	u32 ecx;
	u32 edx;
	u64 __reserved;
} __packed;

/*
 * SNP CPUID table, as defined by the SNP Firmware ABI, Revision 0.9,
 * Section 8.14.2.6. Also noted there is the SNP firmware-enforced limit
 * of 64 entries per CPUID table.
 */
#define SNP_CPUID_COUNT_MAX 64

struct snp_cpuid_table {
	u32 count;
	u32 __reserved1;
	u64 __reserved2;
	struct snp_cpuid_fn fn[SNP_CPUID_COUNT_MAX];
} __packed;

/*
 * Since feature negotiation related variables are set early in the boot
 * process they must reside in the .data section so as not to be zeroed
 * out when the .bss section is later cleared.
 *
 * GHCB protocol version negotiated with the hypervisor.
 */
static u16 ghcb_version __ro_after_init;

/* Copy of the SNP firmware's CPUID page. */
static struct snp_cpuid_table cpuid_table_copy __ro_after_init;

/*
 * These will be initialized based on CPUID table so that non-present
 * all-zero leaves (for sparse tables) can be differentiated from
 * invalid/out-of-range leaves. This is needed since all-zero leaves
 * still need to be post-processed.
 */
static u32 cpuid_std_range_max __ro_after_init;
static u32 cpuid_hyp_range_max __ro_after_init;
static u32 cpuid_ext_range_max __ro_after_init;

static bool __init sev_es_check_cpu_features(void)
{
	if (!has_cpuflag(X86_FEATURE_RDRAND)) {
		error("RDRAND instruction not supported - no trusted source of randomness available\n");
		return false;
	}

	return true;
}

static void __noreturn sev_es_terminate(unsigned int set, unsigned int reason)
{
	u64 val = GHCB_MSR_TERM_REQ;

	/* Tell the hypervisor what went wrong. */
	val |= GHCB_SEV_TERM_REASON(set, reason);

	/* Request Guest Termination from Hypvervisor */
	sev_es_wr_ghcb_msr(val);
	VMGEXIT();

	while (true)
		asm volatile("hlt\n" : : : "memory");
}

/*
 * The hypervisor features are available from GHCB version 2 onward.
 */
static u64 get_hv_features(void)
{
	u64 val;

	if (ghcb_version < 2)
		return 0;

	sev_es_wr_ghcb_msr(GHCB_MSR_HV_FT_REQ);
	VMGEXIT();

	val = sev_es_rd_ghcb_msr();
	if (GHCB_RESP_CODE(val) != GHCB_MSR_HV_FT_RESP)
		return 0;

	return GHCB_MSR_HV_FT_RESP_VAL(val);
}

static void snp_register_ghcb_early(unsigned long paddr)
{
	unsigned long pfn = paddr >> PAGE_SHIFT;
	u64 val;

	sev_es_wr_ghcb_msr(GHCB_MSR_REG_GPA_REQ_VAL(pfn));
	VMGEXIT();

	val = sev_es_rd_ghcb_msr();

	/* If the response GPA is not ours then abort the guest */
	if ((GHCB_RESP_CODE(val) != GHCB_MSR_REG_GPA_RESP) ||
	    (GHCB_MSR_REG_GPA_RESP_VAL(val) != pfn))
		sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_REGISTER);
}

static bool sev_es_negotiate_protocol(void)
{
	u64 val;

	/* Do the GHCB protocol version negotiation */
	sev_es_wr_ghcb_msr(GHCB_MSR_SEV_INFO_REQ);
	VMGEXIT();
	val = sev_es_rd_ghcb_msr();

	if (GHCB_MSR_INFO(val) != GHCB_MSR_SEV_INFO_RESP)
		return false;

	if (GHCB_MSR_PROTO_MAX(val) < GHCB_PROTOCOL_MIN ||
	    GHCB_MSR_PROTO_MIN(val) > GHCB_PROTOCOL_MAX)
		return false;

	ghcb_version = min_t(size_t, GHCB_MSR_PROTO_MAX(val), GHCB_PROTOCOL_MAX);

	return true;
}

static __always_inline void vc_ghcb_invalidate(struct ghcb *ghcb)
{
	ghcb->save.sw_exit_code = 0;
	__builtin_memset(ghcb->save.valid_bitmap, 0, sizeof(ghcb->save.valid_bitmap));
}

static bool vc_decoding_needed(unsigned long exit_code)
{
	/* Exceptions don't require to decode the instruction */
	return !(exit_code >= SVM_EXIT_EXCP_BASE &&
		 exit_code <= SVM_EXIT_LAST_EXCP);
}

static enum es_result vc_init_em_ctxt(struct es_em_ctxt *ctxt,
				      struct pt_regs *regs,
				      unsigned long exit_code)
{
	enum es_result ret = ES_OK;

	memset(ctxt, 0, sizeof(*ctxt));
	ctxt->regs = regs;

	if (vc_decoding_needed(exit_code))
		ret = vc_decode_insn(ctxt);

	return ret;
}

static void vc_finish_insn(struct es_em_ctxt *ctxt)
{
	ctxt->regs->ip += ctxt->insn.length;
}

static enum es_result verify_exception_info(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
{
	u32 ret;

	ret = ghcb->save.sw_exit_info_1 & GENMASK_ULL(31, 0);
	if (!ret)
		return ES_OK;

	if (ret == 1) {
		u64 info = ghcb->save.sw_exit_info_2;
		unsigned long v = info & SVM_EVTINJ_VEC_MASK;

		/*