From 0eaeafa10f3b2bd027e95859a6785d4c7fcc174c Mon Sep 17 00:00:00 2001 From: Christian Borntraeger Date: Wed, 7 May 2008 09:22:53 +0200 Subject: [S390] s390-kvm: leave sie context on work. Removes preemption requirement From: Martin Schwidefsky This patch fixes a bug with cpu bound guest on kvm-s390. Sometimes it was impossible to deliver a signal to a spinning guest. We used preemption as a circumvention. The preemption notifiers called vcpu_load, which checked for pending signals and triggered a host intercept. But even with preemption, a sigkill was not delivered immediately. This patch changes the low level host interrupt handler to check for the SIE instruction, if TIF_WORK is set. In that case we change the instruction pointer of the return PSW to rerun the vcpu_run loop. The kvm code sees an intercept reason 0 if that happens. This patch adds accounting for these types of intercept as well. The advantages: - works with and without preemption - signals are delivered immediately - much better host latencies without preemption Acked-by: Carsten Otte Signed-off-by: Christian Borntraeger Signed-off-by: Martin Schwidefsky --- arch/s390/kvm/Kconfig | 1 - arch/s390/kvm/intercept.c | 3 +++ arch/s390/kvm/kvm-s390.c | 5 +---- 3 files changed, 4 insertions(+), 5 deletions(-) (limited to 'arch/s390/kvm') diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig index 1761b74d639..e051cad1f1e 100644 --- a/arch/s390/kvm/Kconfig +++ b/arch/s390/kvm/Kconfig @@ -22,7 +22,6 @@ config KVM select PREEMPT_NOTIFIERS select ANON_INODES select S390_SWITCH_AMODE - select PREEMPT ---help--- Support hosting paravirtualized guest machines using the SIE virtualization capability on the mainframe. This should work diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c index 349581a2610..47a0b642174 100644 --- a/arch/s390/kvm/intercept.c +++ b/arch/s390/kvm/intercept.c @@ -105,6 +105,9 @@ static intercept_handler_t instruction_handlers[256] = { static int handle_noop(struct kvm_vcpu *vcpu) { switch (vcpu->arch.sie_block->icptcode) { + case 0x0: + vcpu->stat.exit_null++; + break; case 0x10: vcpu->stat.exit_external_request++; break; diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index 98d1e73e01f..0ac36a649eb 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -31,6 +31,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = { { "userspace_handled", VCPU_STAT(exit_userspace) }, + { "exit_null", VCPU_STAT(exit_null) }, { "exit_validity", VCPU_STAT(exit_validity) }, { "exit_stop_request", VCPU_STAT(exit_stop_request) }, { "exit_external_request", VCPU_STAT(exit_external_request) }, @@ -221,10 +222,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) vcpu->arch.guest_fpregs.fpc &= FPC_VALID_MASK; restore_fp_regs(&vcpu->arch.guest_fpregs); restore_access_regs(vcpu->arch.guest_acrs); - - if (signal_pending(current)) - atomic_set_mask(CPUSTAT_STOP_INT, - &vcpu->arch.sie_block->cpuflags); } void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu) -- cgit v1.2.3