From 556f2a5231bf3ec4ce98d46434920e31787f79d6 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Fri, 22 Apr 2016 10:38:48 +0100 Subject: MIPS: KVM: Fix preemption warning reading FPU capability MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Reading the KVM_CAP_MIPS_FPU capability returns cpu_has_fpu, however this uses smp_processor_id() to read the current CPU capabilities (since some old MIPS systems could have FPUs present on only a subset of CPUs). We don't support any such systems, so work around the warning by using raw_cpu_has_fpu instead. We should probably instead claim not to support FPU at all if any one CPU is lacking an FPU, but this should do for now. Signed-off-by: James Hogan Cc: Ralf Baechle Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Signed-off-by: Paolo Bonzini --- arch/mips/kvm/mips.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'arch/mips/kvm/mips.c') diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index 70ef1a43c114..ec3fe09ef15c 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -1079,7 +1079,8 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) r = KVM_COALESCED_MMIO_PAGE_OFFSET; break; case KVM_CAP_MIPS_FPU: - r = !!cpu_has_fpu; + /* We don't handle systems with inconsistent cpu_has_fpu */ + r = !!raw_cpu_has_fpu; break; case KVM_CAP_MIPS_MSA: /* -- cgit v1.2.3 From 4ac334295e4f3b996e9feabe36e79e44bf77a06f Mon Sep 17 00:00:00 2001 From: James Hogan Date: Fri, 22 Apr 2016 10:38:49 +0100 Subject: MIPS: KVM: Add missing disable FPU hazard barriers MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add the necessary hazard barriers after disabling the FPU in kvm_lose_fpu(), just to be safe. Signed-off-by: James Hogan Cc: Ralf Baechle Cc: Paolo Bonzini Cc: "Radim Krčmář" Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Signed-off-by: Paolo Bonzini --- arch/mips/kvm/mips.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'arch/mips/kvm/mips.c') diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index ec3fe09ef15c..23b209463238 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -1556,8 +1556,10 @@ void kvm_lose_fpu(struct kvm_vcpu *vcpu) /* Disable MSA & FPU */ disable_msa(); - if (vcpu->arch.fpu_inuse & KVM_MIPS_FPU_FPU) + if (vcpu->arch.fpu_inuse & KVM_MIPS_FPU_FPU) { clear_c0_status(ST0_CU1 | ST0_FR); + disable_fpu_hazard(); + } vcpu->arch.fpu_inuse &= ~(KVM_MIPS_FPU_FPU | KVM_MIPS_FPU_MSA); } else if (vcpu->arch.fpu_inuse & KVM_MIPS_FPU_FPU) { set_c0_status(ST0_CU1); @@ -1568,6 +1570,7 @@ void kvm_lose_fpu(struct kvm_vcpu *vcpu) /* Disable FPU */ clear_c0_status(ST0_CU1 | ST0_FR); + disable_fpu_hazard(); } preempt_enable(); } -- cgit v1.2.3 From 3491caf2755e9f312666712510d80b00c81ff247 Mon Sep 17 00:00:00 2001 From: Christian Borntraeger Date: Fri, 13 May 2016 12:16:35 +0200 Subject: KVM: halt_polling: provide a way to qualify wakeups during poll MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Some wakeups should not be considered a sucessful poll. For example on s390 I/O interrupts are usually floating, which means that _ALL_ CPUs would be considered runnable - letting all vCPUs poll all the time for transactional like workload, even if one vCPU would be enough. This can result in huge CPU usage for large guests. This patch lets architectures provide a way to qualify wakeups if they should be considered a good/bad wakeups in regard to polls. For s390 the implementation will fence of halt polling for anything but known good, single vCPU events. The s390 implementation for floating interrupts does a wakeup for one vCPU, but the interrupt will be delivered by whatever CPU checks first for a pending interrupt. We prefer the woken up CPU by marking the poll of this CPU as "good" poll. This code will also mark several other wakeup reasons like IPI or expired timers as "good". This will of course also mark some events as not sucessful. As KVM on z runs always as a 2nd level hypervisor, we prefer to not poll, unless we are really sure, though. This patch successfully limits the CPU usage for cases like uperf 1byte transactional ping pong workload or wakeup heavy workload like OLTP while still providing a proper speedup. This also introduced a new vcpu stat "halt_poll_no_tuning" that marks wakeups that are considered not good for polling. Signed-off-by: Christian Borntraeger Acked-by: Radim Krčmář (for an earlier version) Cc: David Matlack Cc: Wanpeng Li [Rename config symbol. - Paolo] Signed-off-by: Paolo Bonzini --- arch/mips/kvm/mips.c | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/mips/kvm/mips.c') diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c index 23b209463238..dc052fb5c7a2 100644 --- a/arch/mips/kvm/mips.c +++ b/arch/mips/kvm/mips.c @@ -56,6 +56,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = { { "flush_dcache", VCPU_STAT(flush_dcache_exits), KVM_STAT_VCPU }, { "halt_successful_poll", VCPU_STAT(halt_successful_poll), KVM_STAT_VCPU }, { "halt_attempted_poll", VCPU_STAT(halt_attempted_poll), KVM_STAT_VCPU }, + { "halt_poll_invalid", VCPU_STAT(halt_poll_invalid), KVM_STAT_VCPU }, { "halt_wakeup", VCPU_STAT(halt_wakeup), KVM_STAT_VCPU }, {NULL} }; -- cgit v1.2.3