This is a note to let you know that I've just added the patch titled
powerpc: Fix is_kvm_guest() / kvm_para_available()
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
powerpc-fix-is_kvm_guest-kvm_para_available.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit b30386b044afd2b1a612a9906f5dc057aeedc409
Author: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Date: Wed Jun 23 23:05:14 2021 +1000
powerpc: Fix is_kvm_guest() / kvm_para_available()
[ Upstream commit 95839225639ba7c3d8d7231b542728dcf222bf2d ]
Commit a21d1becaa3f ("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: a21d1becaa3f ("powerpc: Reintroduce is_kvm_guest() as a fast-path check")
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210623130514.2543232-1-mpe@xxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/arch/powerpc/include/asm/kvm_guest.h b/arch/powerpc/include/asm/kvm_guest.h
index 2fca299f7e192..c63105d2c9e7c 100644
--- a/arch/powerpc/include/asm/kvm_guest.h
+++ b/arch/powerpc/include/asm/kvm_guest.h
@@ -16,10 +16,10 @@ static inline bool is_kvm_guest(void)
return static_branch_unlikely(&kvm_guest);
}
-bool check_kvm_guest(void);
+int check_kvm_guest(void);
#else
static inline bool is_kvm_guest(void) { return false; }
-static inline bool check_kvm_guest(void) { return false; }
+static inline int check_kvm_guest(void) { return 0; }
#endif
#endif /* _ASM_POWERPC_KVM_GUEST_H_ */
diff --git a/arch/powerpc/kernel/firmware.c b/arch/powerpc/kernel/firmware.c
index c9e2819b095ab..c7022c41cc314 100644
--- a/arch/powerpc/kernel/firmware.c
+++ b/arch/powerpc/kernel/firmware.c
@@ -23,18 +23,20 @@ EXPORT_SYMBOL_GPL(powerpc_firmware_features);
#if defined(CONFIG_PPC_PSERIES) || defined(CONFIG_KVM_GUEST)
DEFINE_STATIC_KEY_FALSE(kvm_guest);
-bool check_kvm_guest(void)
+int __init check_kvm_guest(void)
{
struct device_node *hyper_node;
hyper_node = of_find_node_by_path("/hypervisor");
if (!hyper_node)
- return false;
+ return 0;
if (!of_device_is_compatible(hyper_node, "linux,kvm"))
- return false;
+ return 0;
static_branch_enable(&kvm_guest);
- return true;
+
+ return 0;
}
+core_initcall(check_kvm_guest); // before kvm_guest_init()
#endif
diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c
index 9d596b41ec675..f47429323eee9 100644
--- a/arch/powerpc/platforms/pseries/smp.c
+++ b/arch/powerpc/platforms/pseries/smp.c
@@ -208,7 +208,9 @@ static __init void pSeries_smp_probe(void)
if (!cpu_has_feature(CPU_FTR_SMT))
return;
- if (check_kvm_guest()) {
+ check_kvm_guest();
+
+ if (is_kvm_guest()) {
/*
* KVM emulates doorbells by disabling FSCR[MSGP] so msgsndp
* faults to the hypervisor which then reads the instruction
