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powerpc: Reintroduce is_kvm_guest() as a fast-path check 

Introduce a static branch that would be set during boot if the OS
happens to be a KVM guest. Subsequent checks to see if we are on KVM
will rely on this static branch. This static branch would be used in
vcpu_is_preempted() in a subsequent patch.

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201202050456.164005-4-srikar@linux.vnet.ibm.com
This commit is contained in:
Srikar Dronamraju 2020-12-02 10:34:55 +05:30 committed by Michael Ellerman
parent 16520a858a
commit a21d1becaa
3 changed files with 13 additions and 1 deletions
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10
arch/powerpc/include/asm/kvm_guest.h
View File

@ -7,8 +7,18 @@
#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);
}
bool check_kvm_guest(void);
#else
static inline bool is_kvm_guest(void) { return false; }
static inline bool check_kvm_guest(void) { return false; }
#endif

2
arch/powerpc/include/asm/kvm_para.h
View File

@ -14,7 +14,7 @@
static inline int kvm_para_available(void)
{
return IS_ENABLED(CONFIG_KVM_GUEST) && check_kvm_guest();
return IS_ENABLED(CONFIG_KVM_GUEST) && is_kvm_guest();
}
static inline unsigned int kvm_arch_para_features(void)

2
arch/powerpc/kernel/firmware.c
View File

@ -22,6 +22,7 @@ EXPORT_SYMBOL_GPL(powerpc_firmware_features);
#endif
#if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_KVM_GUEST)
DEFINE_STATIC_KEY_FALSE(kvm_guest);
bool check_kvm_guest(void)
{
struct device_node *hyper_node;
@ -33,6 +34,7 @@ bool check_kvm_guest(void)
if (!of_device_is_compatible(hyper_node, "linux,kvm"))
return false;
static_branch_enable(&kvm_guest);
return true;
}
#endif