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Implementing this in a hybrid manner seems entirely > unnecessary. I moved sev_prepare() into the EFI stub, and I wrote a wrapper for registering Alternate Injection in the EFI stub but kept the code in compressed, otherwise I have to export early_is_sevsnp_guest(), boot_svsm_caa_pa, and svsm_call_msr_protocol() so that it builds. How about this below: This is in the stub: static bool sev_prepare(void) { u64 unsupported; unsupported = snp_get_unsupported_features(sev_get_status()); if (unsupported) { efi_err("Unsupported SEV-SNP features detected: 0x%llx\n", unsupported); return true; } register_alternate_injection(); return false; } and the stub calls this function: +void register_alternate_injection(void) +{ + if (early_is_sevsnp_guest() && snp_vmpl) { + struct svsm_call call = {}; + int ret; + + if (!(sev_get_status() & MSR_AMD64_SNP_ALTERNATE_INJ)) + return; + + call.caa = (struct svsm_ca *)boot_svsm_caa_pa; + call.rax = SVSM_APIC_CALL(SVSM_APIC_CONFIG_EMULATION); + call.rcx = SVSM_AI_REGISTER; + + ret = svsm_call_msr_protocol(&call); + if (ret) + sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_ALT_INJ_FAIL); + } +} which is kept in sev.c to avoid cross-dependencies. I can send it as patches too if it is easier to review this way. -- Thanks, Melody