linux/arch/powerpc/include/asm/kvm_guest.h
Michael Ellerman 9583922563 powerpc: Fix is_kvm_guest() / kvm_para_available()
Commit a21d1becaa ("powerpc: Reintroduce is_kvm_guest() as a fast-path
check") added is_kvm_guest() and changed kvm_para_available() to use it.

is_kvm_guest() checks a static key, kvm_guest, and that static key is
set in check_kvm_guest().

The problem is check_kvm_guest() is only called on pseries, and even
then only in some configurations. That means is_kvm_guest() always
returns false on all non-pseries and some pseries depending on
configuration. That's a bug.

For PR KVM guests this is noticable because they no longer do live
patching of themselves, which can be detected by the omission of a
message in dmesg such as:

  KVM: Live patching for a fast VM worked

To fix it make check_kvm_guest() an initcall, to ensure it's always
called at boot. It needs to be core so that it runs before
kvm_guest_init() which is postcore. To be an initcall it needs to return
int, where 0 means success, so update that.

We still call it manually in pSeries_smp_probe(), because that runs
before init calls are run.

Fixes: a21d1becaa ("powerpc: Reintroduce is_kvm_guest() as a fast-path check")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210623130514.2543232-1-mpe@ellerman.id.au
2021-06-25 14:47:19 +10:00

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C

/* SPDX-License-Identifier: GPL-2.0-only */
/*
* Copyright (C) 2020 IBM Corporation
*/
#ifndef _ASM_POWERPC_KVM_GUEST_H_
#define _ASM_POWERPC_KVM_GUEST_H_
#if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_KVM_GUEST)
#include <linux/jump_label.h>
DECLARE_STATIC_KEY_FALSE(kvm_guest);
static inline bool is_kvm_guest(void)
{
return static_branch_unlikely(&kvm_guest);
}
int check_kvm_guest(void);
#else
static inline bool is_kvm_guest(void) { return false; }
static inline int check_kvm_guest(void) { return 0; }
#endif
#endif /* _ASM_POWERPC_KVM_GUEST_H_ */