1 // SPDX-License-Identifier: GPL-2.0 2 3 /* 4 * Architecture neutral utility routines for interacting with 5 * Hyper-V. This file is specifically for code that must be 6 * built-in to the kernel image when CONFIG_HYPERV is set 7 * (vs. being in a module) because it is called from architecture 8 * specific code under arch/. 9 * 10 * Copyright (C) 2021, Microsoft, Inc. 11 * 12 * Author : Michael Kelley <mikelley@microsoft.com> 13 */ 14 15 #include <linux/types.h> 16 #include <linux/export.h> 17 #include <linux/bitfield.h> 18 #include <asm/hyperv-tlfs.h> 19 #include <asm/mshyperv.h> 20 21 22 /* Bit mask of the extended capability to query: see HV_EXT_CAPABILITY_xxx */ 23 bool hv_query_ext_cap(u64 cap_query) 24 { 25 /* 26 * The address of the 'hv_extended_cap' variable will be used as an 27 * output parameter to the hypercall below and so it should be 28 * compatible with 'virt_to_phys'. Which means, it's address should be 29 * directly mapped. Use 'static' to keep it compatible; stack variables 30 * can be virtually mapped, making them incompatible with 31 * 'virt_to_phys'. 32 * Hypercall input/output addresses should also be 8-byte aligned. 33 */ 34 static u64 hv_extended_cap __aligned(8); 35 static bool hv_extended_cap_queried; 36 u64 status; 37 38 /* 39 * Querying extended capabilities is an extended hypercall. Check if the 40 * partition supports extended hypercall, first. 41 */ 42 if (!(ms_hyperv.priv_high & HV_ENABLE_EXTENDED_HYPERCALLS)) 43 return false; 44 45 /* Extended capabilities do not change at runtime. */ 46 if (hv_extended_cap_queried) 47 return hv_extended_cap & cap_query; 48 49 status = hv_do_hypercall(HV_EXT_CALL_QUERY_CAPABILITIES, NULL, 50 &hv_extended_cap); 51 52 /* 53 * The query extended capabilities hypercall should not fail under 54 * any normal circumstances. Avoid repeatedly making the hypercall, on 55 * error. 56 */ 57 hv_extended_cap_queried = true; 58 if (!hv_result_success(status)) { 59 pr_err("Hyper-V: Extended query capabilities hypercall failed 0x%llx\n", 60 status); 61 return false; 62 } 63 64 return hv_extended_cap & cap_query; 65 } 66 EXPORT_SYMBOL_GPL(hv_query_ext_cap); 67