// SPDX-License-Identifier: GPL-2.0
/*
 * AMD Encrypted Register State Support
 *
 * Author: Joerg Roedel <jroedel@suse.de>
 */

/*
 * misc.h needs to be first because it knows how to include the other kernel
 * headers in the pre-decompression code in a way that does not break
 * compilation.
 */
#include "misc.h"

#include <asm/bootparam.h>
#include <asm/pgtable_types.h>
#include <asm/shared/msr.h>
#include <asm/sev.h>
#include <asm/trapnr.h>
#include <asm/trap_pf.h>
#include <asm/msr-index.h>
#include <asm/fpu/xcr.h>
#include <asm/ptrace.h>
#include <asm/svm.h>
#include <asm/cpuid/api.h>

#include "error.h"
#include "sev.h"

static struct ghcb boot_ghcb_page __aligned(PAGE_SIZE);
struct ghcb *boot_ghcb __section(".data");

#undef __init
#define __init

#define __BOOT_COMPRESSED

u8 snp_vmpl __section(".data");
u16 ghcb_version __section(".data");

u64 boot_svsm_caa_pa __section(".data");

/* Include code for early handlers */
#include "../../boot/startup/sev-shared.c"

static bool sev_snp_enabled(void)
{
        return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
}

void snp_set_page_private(unsigned long paddr)
{
        struct psc_desc d = {
                SNP_PAGE_STATE_PRIVATE,
                (struct svsm_ca *)boot_svsm_caa_pa,
                boot_svsm_caa_pa
        };

        if (!sev_snp_enabled())
                return;

        __page_state_change(paddr, paddr, &d);
}

void snp_set_page_shared(unsigned long paddr)
{
        struct psc_desc d = {
                SNP_PAGE_STATE_SHARED,
                (struct svsm_ca *)boot_svsm_caa_pa,
                boot_svsm_caa_pa
        };

        if (!sev_snp_enabled())
                return;

        __page_state_change(paddr, paddr, &d);
}

bool early_setup_ghcb(void)
{
        if (set_page_decrypted((unsigned long)&boot_ghcb_page))
                return false;

        /* Page is now mapped decrypted, clear it */
        memset(&boot_ghcb_page, 0, sizeof(boot_ghcb_page));

        boot_ghcb = &boot_ghcb_page;

        /* Initialize lookup tables for the instruction decoder */
        sev_insn_decode_init();

        /* SNP guest requires the GHCB GPA must be registered */
        if (sev_snp_enabled())
                snp_register_ghcb_early(__pa(&boot_ghcb_page));

        return true;
}

void snp_accept_memory(phys_addr_t start, phys_addr_t end)
{
        struct psc_desc d = {
                SNP_PAGE_STATE_PRIVATE,
                (struct svsm_ca *)boot_svsm_caa_pa,
                boot_svsm_caa_pa
        };

        for (phys_addr_t pa = start; pa < end; pa += PAGE_SIZE)
                __page_state_change(pa, pa, &d);
}

void sev_es_shutdown_ghcb(void)
{
        if (!boot_ghcb)
                return;

        if (!sev_es_check_cpu_features())
                error("SEV-ES CPU Features missing.");

        /*
         * This denotes whether to use the GHCB MSR protocol or the GHCB
         * shared page to perform a GHCB request. Since the GHCB page is
         * being changed to encrypted, it can't be used to perform GHCB
         * requests. Clear the boot_ghcb variable so that the GHCB MSR
         * protocol is used to change the GHCB page over to an encrypted
         * page.
         */
        boot_ghcb = NULL;

        /*
         * GHCB Page must be flushed from the cache and mapped encrypted again.
         * Otherwise the running kernel will see strange cache effects when
         * trying to use that page.
         */
        if (set_page_encrypted((unsigned long)&boot_ghcb_page))
                error("Can't map GHCB page encrypted");

        /*
         * GHCB page is mapped encrypted again and flushed from the cache.
         * Mark it non-present now to catch bugs when #VC exceptions trigger
         * after this point.
         */
        if (set_page_non_present((unsigned long)&boot_ghcb_page))
                error("Can't unmap GHCB page");
}

static void __noreturn sev_es_ghcb_terminate(struct ghcb *ghcb, unsigned int set,
                                             unsigned int reason, u64 exit_info_2)
{
        u64 exit_info_1 = SVM_VMGEXIT_TERM_REASON(set, reason);

        vc_ghcb_invalidate(ghcb);
        ghcb_set_sw_exit_code(ghcb, SVM_VMGEXIT_TERM_REQUEST);
        ghcb_set_sw_exit_info_1(ghcb, exit_info_1);
        ghcb_set_sw_exit_info_2(ghcb, exit_info_2);

        sev_es_wr_ghcb_msr(__pa(ghcb));
        VMGEXIT();

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

bool sev_es_check_ghcb_fault(unsigned long address)
{
        /* Check whether the fault was on the GHCB page */
        return ((address & PAGE_MASK) == (unsigned long)&boot_ghcb_page);
}

/*
 * SNP_FEATURES_IMPL_REQ is the mask of SNP features that will need
 * guest side implementation for proper functioning of the guest. If any
 * of these features are enabled in the hypervisor but are lacking guest
 * side implementation, the behavior of the guest will be undefined. The
 * guest could fail in non-obvious way making it difficult to debug.
 *
 * As the behavior of reserved feature bits is unknown to be on the
 * safe side add them to the required features mask.
 */
#define SNP_FEATURES_IMPL_REQ   (MSR_AMD64_SNP_VTOM |                   \
                                 MSR_AMD64_SNP_REFLECT_VC |             \
                                 MSR_AMD64_SNP_RESTRICTED_INJ |         \
                                 MSR_AMD64_SNP_ALT_INJ |                \
                                 MSR_AMD64_SNP_DEBUG_SWAP |             \
                                 MSR_AMD64_SNP_VMPL_SSS |               \
                                 MSR_AMD64_SNP_SECURE_TSC |             \
                                 MSR_AMD64_SNP_VMGEXIT_PARAM |          \
                                 MSR_AMD64_SNP_VMSA_REG_PROT |          \
                                 MSR_AMD64_SNP_RESERVED_BIT13 |         \
                                 MSR_AMD64_SNP_RESERVED_BIT15 |         \
                                 MSR_AMD64_SNP_SECURE_AVIC |            \
                                 MSR_AMD64_SNP_RESERVED_BITS19_22 |     \
                                 MSR_AMD64_SNP_RESERVED_MASK)

#ifdef CONFIG_AMD_SECURE_AVIC
#define SNP_FEATURE_SECURE_AVIC         MSR_AMD64_SNP_SECURE_AVIC
#else
#define SNP_FEATURE_SECURE_AVIC         0
#endif

/*
 * SNP_FEATURES_PRESENT is the mask of SNP features that are implemented
 * by the guest kernel. As and when a new feature is implemented in the
 * guest kernel, a corresponding bit should be added to the mask.
 */
#define SNP_FEATURES_PRESENT    (MSR_AMD64_SNP_DEBUG_SWAP |     \
                                 MSR_AMD64_SNP_SECURE_TSC |     \
                                 SNP_FEATURE_SECURE_AVIC)

u64 snp_get_unsupported_features(u64 status)
{
        if (!(status & MSR_AMD64_SEV_SNP_ENABLED))
                return 0;

        return status & SNP_FEATURES_IMPL_REQ & ~SNP_FEATURES_PRESENT;
}

void snp_check_features(void)
{
        u64 unsupported;

        /*
         * Terminate the boot if hypervisor has enabled any feature lacking
         * guest side implementation. Pass on the unsupported features mask through
         * EXIT_INFO_2 of the GHCB protocol so that those features can be reported
         * as part of the guest boot failure.
         */
        unsupported = snp_get_unsupported_features(sev_status);
        if (unsupported) {
                if (ghcb_version < 2 || (!boot_ghcb && !early_setup_ghcb()))
                        sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);

                sev_es_ghcb_terminate(boot_ghcb, SEV_TERM_SET_GEN,
                                      GHCB_SNP_UNSUPPORTED, unsupported);
        }
}

/* Search for Confidential Computing blob in the EFI config table. */
static struct cc_blob_sev_info *find_cc_blob_efi(struct boot_params *bp)
{
        unsigned long cfg_table_pa;
        unsigned int cfg_table_len;
        int ret;

        ret = efi_get_conf_table(bp, &cfg_table_pa, &cfg_table_len);
        if (ret)
                return NULL;

        return (struct cc_blob_sev_info *)efi_find_vendor_table(bp, cfg_table_pa,
                                                                cfg_table_len,
                                                                EFI_CC_BLOB_GUID);
}

/*
 * Initial set up of SNP relies on information provided by the
 * Confidential Computing blob, which can be passed to the boot kernel
 * by firmware/bootloader in the following ways:
 *
 * - via an entry in the EFI config table
 * - via a setup_data structure, as defined by the Linux Boot Protocol
 *
 * Scan for the blob in that order.
 */
static struct cc_blob_sev_info *find_cc_blob(struct boot_params *bp)
{
        struct cc_blob_sev_info *cc_info;

        cc_info = find_cc_blob_efi(bp);
        if (cc_info)
                goto found_cc_info;

        cc_info = find_cc_blob_setup_data(bp);
        if (!cc_info)
                return NULL;

found_cc_info:
        if (cc_info->magic != CC_BLOB_SEV_HDR_MAGIC)
                sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);

        return cc_info;
}

/*
 * Indicate SNP based on presence of SNP-specific CC blob. Subsequent checks
 * will verify the SNP CPUID/MSR bits.
 */
static bool early_snp_init(struct boot_params *bp)
{
        struct cc_blob_sev_info *cc_info;

        if (!bp)
                return false;

        cc_info = find_cc_blob(bp);
        if (!cc_info)
                return false;

        /*
         * If a SNP-specific Confidential Computing blob is present, then
         * firmware/bootloader have indicated SNP support. Verifying this
         * involves CPUID checks which will be more reliable if the SNP
         * CPUID table is used. See comments over snp_setup_cpuid_table() for
         * more details.
         */
        setup_cpuid_table(cc_info);

        /*
         * Record the SVSM Calling Area (CA) address if the guest is not
         * running at VMPL0. The CA will be used to communicate with the
         * SVSM and request its services.
         */
        svsm_setup_ca(cc_info, rip_rel_ptr(&boot_ghcb_page));

        /*
         * Pass run-time kernel a pointer to CC info via boot_params so EFI
         * config table doesn't need to be searched again during early startup
         * phase.
         */
        bp->cc_blob_address = (u32)(unsigned long)cc_info;

        return true;
}

/*
 * sev_check_cpu_support - Check for SEV support in the CPU capabilities
 *
 * Returns < 0 if SEV is not supported, otherwise the position of the
 * encryption bit in the page table descriptors.
 */
static int sev_check_cpu_support(void)
{
        unsigned int eax, ebx, ecx, edx;

        /* Check for the SME/SEV support leaf */
        eax = 0x80000000;
        ecx = 0;
        native_cpuid(&eax, &ebx, &ecx, &edx);
        if (eax < 0x8000001f)
                return -ENODEV;

        /*
         * Check for the SME/SEV feature:
         *   CPUID Fn8000_001F[EAX]
         *   - Bit 0 - Secure Memory Encryption support
         *   - Bit 1 - Secure Encrypted Virtualization support
         *   CPUID Fn8000_001F[EBX]
         *   - Bits 5:0 - Pagetable bit position used to indicate encryption
         */
        eax = 0x8000001f;
        ecx = 0;
        native_cpuid(&eax, &ebx, &ecx, &edx);
        /* Check whether SEV is supported */
        if (!(eax & BIT(1)))
                return -ENODEV;

        sev_snp_needs_sfw = !(ebx & BIT(31));

        return ebx & 0x3f;
}

void sev_enable(struct boot_params *bp)
{
        struct msr m;
        int bitpos;
        bool snp;

        /*
         * bp->cc_blob_address should only be set by boot/compressed kernel.
         * Initialize it to 0 to ensure that uninitialized values from
         * buggy bootloaders aren't propagated.
         */
        if (bp)
                bp->cc_blob_address = 0;

        /*
         * Do an initial SEV capability check before early_snp_init() which
         * loads the CPUID page and the same checks afterwards are done
         * without the hypervisor and are trustworthy.
         *
         * If the HV fakes SEV support, the guest will crash'n'burn
         * which is good enough.
         */

        if (sev_check_cpu_support() < 0)
                return;

        /*
         * Setup/preliminary detection of SNP. This will be sanity-checked
         * against CPUID/MSR values later.
         */
        snp = early_snp_init(bp);

        /* Now repeat the checks with the SNP CPUID table. */

        bitpos = sev_check_cpu_support();
        if (bitpos < 0) {
                if (snp)
                        error("SEV-SNP support indicated by CC blob, but not CPUID.");
                return;
        }

        /* Set the SME mask if this is an SEV guest. */
        raw_rdmsr(MSR_AMD64_SEV, &m);
        sev_status = m.q;
        if (!(sev_status & MSR_AMD64_SEV_ENABLED))
                return;

        /* Negotiate the GHCB protocol version. */
        if (sev_status & MSR_AMD64_SEV_ES_ENABLED) {
                if (!sev_es_negotiate_protocol())
                        sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_PROT_UNSUPPORTED);
        }

        /*
         * SNP is supported in v2 of the GHCB spec which mandates support for HV
         * features.
         */
        if (sev_status & MSR_AMD64_SEV_SNP_ENABLED) {
                u64 hv_features;

                hv_features = get_hv_features();
                if (!(hv_features & GHCB_HV_FT_SNP))
                        sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SNP_UNSUPPORTED);

                /*
                 * Running at VMPL0 is required unless an SVSM is present and
                 * the hypervisor supports the required SVSM GHCB events.
                 */
                if (snp_vmpl && !(hv_features & GHCB_HV_FT_SNP_MULTI_VMPL))
                        sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_NOT_VMPL0);
        }

        if (snp && !(sev_status & MSR_AMD64_SEV_SNP_ENABLED))
                error("SEV-SNP supported indicated by CC blob, but not SEV status MSR.");

        sme_me_mask = BIT_ULL(bitpos);
}

/*
 * sev_get_status - Retrieve the SEV status mask
 *
 * Returns 0 if the CPU is not SEV capable, otherwise the value of the
 * AMD64_SEV MSR.
 */
u64 sev_get_status(void)
{
        struct msr m;

        if (sev_check_cpu_support() < 0)
                return 0;

        raw_rdmsr(MSR_AMD64_SEV, &m);
        return m.q;
}

void sev_prep_identity_maps(unsigned long top_level_pgt)
{
        /*
         * The Confidential Computing blob is used very early in uncompressed
         * kernel to find the in-memory CPUID table to handle CPUID
         * instructions. Make sure an identity-mapping exists so it can be
         * accessed after switchover.
         */
        if (sev_snp_enabled()) {
                unsigned long cc_info_pa = boot_params_ptr->cc_blob_address;
                struct cc_blob_sev_info *cc_info;

                kernel_add_identity_map(cc_info_pa, cc_info_pa + sizeof(*cc_info));

                cc_info = (struct cc_blob_sev_info *)cc_info_pa;
                kernel_add_identity_map(cc_info->cpuid_phys, cc_info->cpuid_phys + cc_info->cpuid_len);
        }

        sev_verify_cbit(top_level_pgt);
}

bool early_is_sevsnp_guest(void)
{
        static bool sevsnp;

        if (sevsnp)
                return true;

        if (!(sev_get_status() & MSR_AMD64_SEV_SNP_ENABLED))
                return false;

        sevsnp = true;

        if (!snp_vmpl) {
                unsigned int eax, ebx, ecx, edx;

                /*
                 * CPUID Fn8000_001F_EAX[28] - SVSM support
                 */
                eax = 0x8000001f;
                ecx = 0;
                native_cpuid(&eax, &ebx, &ecx, &edx);
                if (eax & BIT(28)) {
                        struct msr m;

                        /* Obtain the address of the calling area to use */
                        raw_rdmsr(MSR_SVSM_CAA, &m);
                        boot_svsm_caa_pa = m.q;

                        /*
                         * The real VMPL level cannot be discovered, but the
                         * memory acceptance routines make no use of that so
                         * any non-zero value suffices here.
                         */
                        snp_vmpl = U8_MAX;
                }
        }
        return true;
}