Message ID | 20210623130514.2543232-1-mpe@ellerman.id.au (mailing list archive) |
---|---|
State | Accepted |
Headers | show |
Series | powerpc: Fix is_kvm_guest() / kvm_para_available() | expand |
Context | Check | Description |
---|---|---|
snowpatch_ozlabs/apply_patch | success | Successfully applied on branch powerpc/merge (7f030e9d57b8ff6025bde4162f42378e6081126a) |
snowpatch_ozlabs/build-ppc64le | success | Build succeeded |
snowpatch_ozlabs/build-ppc64be | success | Build succeeded |
snowpatch_ozlabs/build-ppc64e | success | Build succeeded |
snowpatch_ozlabs/build-pmac32 | success | Build succeeded |
snowpatch_ozlabs/checkpatch | warning | total: 0 errors, 1 warnings, 0 checks, 46 lines checked |
snowpatch_ozlabs/needsstable | warning | Please consider tagging this patch for stable! |
On Wed, 23 Jun 2021 23:05:14 +1000, Michael Ellerman wrote: > 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. > > [...] Applied to powerpc/next. [1/1] powerpc: Fix is_kvm_guest() / kvm_para_available() https://git.kernel.org/powerpc/c/95839225639ba7c3d8d7231b542728dcf222bf2d cheers
diff --git a/arch/powerpc/include/asm/kvm_guest.h b/arch/powerpc/include/asm/kvm_guest.h index 2fca299f7e19..c63105d2c9e7 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 c9e2819b095a..c7022c41cc31 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 c70b4be9f0a5..096629f54576 100644 --- a/arch/powerpc/platforms/pseries/smp.c +++ b/arch/powerpc/platforms/pseries/smp.c @@ -211,7 +211,9 @@ 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
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@ellerman.id.au> --- arch/powerpc/include/asm/kvm_guest.h | 4 ++-- arch/powerpc/kernel/firmware.c | 10 ++++++---- arch/powerpc/platforms/pseries/smp.c | 4 +++- 3 files changed, 11 insertions(+), 7 deletions(-)