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67 lines
2.0 KiB
C
67 lines
2.0 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* Architecture neutral utility routines for interacting with
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* Hyper-V. This file is specifically for code that must be
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* built-in to the kernel image when CONFIG_HYPERV is set
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* (vs. being in a module) because it is called from architecture
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* specific code under arch/.
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*
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* Copyright (C) 2021, Microsoft, Inc.
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*
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* Author : Michael Kelley <mikelley@microsoft.com>
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*/
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#include <linux/types.h>
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#include <linux/export.h>
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#include <linux/bitfield.h>
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#include <asm/hyperv-tlfs.h>
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#include <asm/mshyperv.h>
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/* Bit mask of the extended capability to query: see HV_EXT_CAPABILITY_xxx */
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bool hv_query_ext_cap(u64 cap_query)
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{
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/*
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* The address of the 'hv_extended_cap' variable will be used as an
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* output parameter to the hypercall below and so it should be
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* compatible with 'virt_to_phys'. Which means, it's address should be
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* directly mapped. Use 'static' to keep it compatible; stack variables
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* can be virtually mapped, making them imcompatible with
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* 'virt_to_phys'.
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* Hypercall input/output addresses should also be 8-byte aligned.
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*/
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static u64 hv_extended_cap __aligned(8);
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static bool hv_extended_cap_queried;
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u64 status;
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/*
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* Querying extended capabilities is an extended hypercall. Check if the
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* partition supports extended hypercall, first.
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*/
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if (!(ms_hyperv.priv_high & HV_ENABLE_EXTENDED_HYPERCALLS))
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return false;
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/* Extended capabilities do not change at runtime. */
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if (hv_extended_cap_queried)
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return hv_extended_cap & cap_query;
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status = hv_do_hypercall(HV_EXT_CALL_QUERY_CAPABILITIES, NULL,
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&hv_extended_cap);
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/*
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* The query extended capabilities hypercall should not fail under
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* any normal circumstances. Avoid repeatedly making the hypercall, on
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* error.
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*/
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hv_extended_cap_queried = true;
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if (!hv_result_success(status)) {
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pr_err("Hyper-V: Extended query capabilities hypercall failed 0x%llx\n",
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status);
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return false;
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}
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return hv_extended_cap & cap_query;
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}
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EXPORT_SYMBOL_GPL(hv_query_ext_cap);
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