| Message ID | 1487194670-6319-2-git-send-email-longman@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Feb 15, 2017 at 04:37:49PM -0500, Waiman Long wrote: > The cpu argument in the function prototype of vcpu_is_preempted() > is changed from int to long. That makes it easier to provide a better > optimized assembly version of that function. > > For Xen, vcpu_is_preempted(long) calls xen_vcpu_stolen(int), the > downcast from long to int is not a problem as vCPU number won't exceed > 32 bits. > Note that because of the cast in PVOP_CALL_ARG1() this patch is pointless. Then again, it doesn't seem to affect code generation, so why not. Takes away the reliance on that weird cast.
On 02/16/2017 11:09 AM, Peter Zijlstra wrote: > On Wed, Feb 15, 2017 at 04:37:49PM -0500, Waiman Long wrote: >> The cpu argument in the function prototype of vcpu_is_preempted() >> is changed from int to long. That makes it easier to provide a better >> optimized assembly version of that function. >> >> For Xen, vcpu_is_preempted(long) calls xen_vcpu_stolen(int), the >> downcast from long to int is not a problem as vCPU number won't exceed >> 32 bits. >> > Note that because of the cast in PVOP_CALL_ARG1() this patch is > pointless. > > Then again, it doesn't seem to affect code generation, so why not. Takes > away the reliance on that weird cast. I add this patch because I am a bit uneasy about clearing the upper 32 bits of rdi and assuming that the compiler won't have a previous use of those bits. It gives me peace of mind. Cheers, Longman
On Thu, Feb 16, 2017 at 04:02:57PM -0500, Waiman Long wrote: > On 02/16/2017 11:09 AM, Peter Zijlstra wrote: > > On Wed, Feb 15, 2017 at 04:37:49PM -0500, Waiman Long wrote: > >> The cpu argument in the function prototype of vcpu_is_preempted() > >> is changed from int to long. That makes it easier to provide a better > >> optimized assembly version of that function. > >> > >> For Xen, vcpu_is_preempted(long) calls xen_vcpu_stolen(int), the > >> downcast from long to int is not a problem as vCPU number won't exceed > >> 32 bits. > >> > > Note that because of the cast in PVOP_CALL_ARG1() this patch is > > pointless. > > > > Then again, it doesn't seem to affect code generation, so why not. Takes > > away the reliance on that weird cast. > > I add this patch because I am a bit uneasy about clearing the upper 32 > bits of rdi and assuming that the compiler won't have a previous use of > those bits. It gives me peace of mind. So currently the PVOP_CALL_ARG#() macros force cast everything to (unsigned long) anyway, but it would be good not to rely on that I think, so yes.
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h index 1eea6ca..f75fbfe 100644 --- a/arch/x86/include/asm/paravirt.h +++ b/arch/x86/include/asm/paravirt.h @@ -673,7 +673,7 @@ static __always_inline void pv_kick(int cpu) PVOP_VCALL1(pv_lock_ops.kick, cpu); } -static __always_inline bool pv_vcpu_is_preempted(int cpu) +static __always_inline bool pv_vcpu_is_preempted(long cpu) { return PVOP_CALLEE1(bool, pv_lock_ops.vcpu_is_preempted, cpu); } diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h index c343ab5..48a706f 100644 --- a/arch/x86/include/asm/qspinlock.h +++ b/arch/x86/include/asm/qspinlock.h @@ -34,7 +34,7 @@ static inline void queued_spin_unlock(struct qspinlock *lock) } #define vcpu_is_preempted vcpu_is_preempted -static inline bool vcpu_is_preempted(int cpu) +static inline bool vcpu_is_preempted(long cpu) { return pv_vcpu_is_preempted(cpu); } diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 099fcba..85ed343 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -589,7 +589,7 @@ static void kvm_wait(u8 *ptr, u8 val) local_irq_restore(flags); } -__visible bool __kvm_vcpu_is_preempted(int cpu) +__visible bool __kvm_vcpu_is_preempted(long cpu) { struct kvm_steal_time *src = &per_cpu(steal_time, cpu); diff --git a/arch/x86/kernel/paravirt-spinlocks.c b/arch/x86/kernel/paravirt-spinlocks.c index 6259327..8f2d1c9 100644 --- a/arch/x86/kernel/paravirt-spinlocks.c +++ b/arch/x86/kernel/paravirt-spinlocks.c @@ -20,7 +20,7 @@ bool pv_is_native_spin_unlock(void) __raw_callee_save___native_queued_spin_unlock; } -__visible bool __native_vcpu_is_preempted(int cpu) +__visible bool __native_vcpu_is_preempted(long cpu) { return false; }
The cpu argument in the function prototype of vcpu_is_preempted() is changed from int to long. That makes it easier to provide a better optimized assembly version of that function. For Xen, vcpu_is_preempted(long) calls xen_vcpu_stolen(int), the downcast from long to int is not a problem as vCPU number won't exceed 32 bits. Signed-off-by: Waiman Long <longman@redhat.com> --- arch/x86/include/asm/paravirt.h | 2 +- arch/x86/include/asm/qspinlock.h | 2 +- arch/x86/kernel/kvm.c | 2 +- arch/x86/kernel/paravirt-spinlocks.c | 2 +- 4 files changed, 4 insertions(+), 4 deletions(-)