From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> To: Gleb Natapov <gleb@redhat.com> Cc: Jeremy Fitzhardinge <jeremy@goop.org>, KVM <kvm@vger.kernel.org>, linux-doc@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, Jan Kiszka <jan.kiszka@siemens.com>, Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>, Paul Mackerras <paulus@samba.org>, "H. Peter Anvin" <hpa@zytor.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Xen <xen-devel@lists.xensource.com>, Dave Jiang <dave.jiang@intel.com>, Glauber Costa <glommer@redhat.com>, X86 <x86@kernel.org>, Ingo Molnar <mingo@redhat.com>, Avi Kivity <avi@redhat.com>, Rik van Riel <riel@redhat.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Sasha Levin <levinsasha928@gmail.com>, Sedat Dilek <sedat.dilek@gmail.com>, Thomas Gleixner <tglx@linutronix.de>, Virtualization <virtualization@lists.linux-foundation.org>, Greg Kroah-Hartman <gregkh@suse.de>, LKML <linux-kernel@vger.kernel.org>, Dave Hansen <dave@linu Subject: Re: [PATCH RFC V4 5/5] Documentation/kvm : Add documentation on Hypercalls and features used for PV spinlock Date: Tue, 17 Jan 2012 18:43:33 +0530 [thread overview] Message-ID: <4F1573FD.3030604@linux.vnet.ibm.com> (raw) In-Reply-To: <20120117125126.GQ2167@redhat.com> On 01/17/2012 06:21 PM, Gleb Natapov wrote: > On Tue, Jan 17, 2012 at 05:56:50PM +0530, Srivatsa Vaddagiri wrote: >> * Gleb Natapov<gleb@redhat.com> [2012-01-17 11:14:13]: >> >>>> The problem case I was thinking of was when guest VCPU would have issued >>>> HLT with interrupts disabled. I guess one option is to inject an NMI, >>>> and have the guest kernel NMI handler recognize this and make >>>> adjustments such that the vcpu avoids going back to HLT instruction. >>>> >>> Just kick vcpu out of a guest mode and adjust rip to point after HLT on >>> next re-entry. Don't forget to call vmx_clear_hlt(). >> >> Looks bit hackish to me compared to having another hypercall to yield! >> > Do not see anything hackish about it. But what you described above (the > part I replied to) is not another hypercall, but yet another NMI source > and special handling in a guest. So what hypercall do you mean? > Earlier version had a hypercall to sleep instead of current halt() approach. This was taken out to avoid extra hypercall. So here is the hypercall hunk referred : +/* + * kvm_pv_wait_for_kick_op : Block until kicked by either a KVM_HC_KICK_CPU + * hypercall or a event like interrupt. + * + * @vcpu : vcpu which is blocking. + */ +static void kvm_pv_wait_for_kick_op(struct kvm_vcpu *vcpu) +{ + DEFINE_WAIT(wait); + + /* + * Blocking on vcpu->wq allows us to wake up sooner if required to + * service pending events (like interrupts). + * + * Also set state to TASK_INTERRUPTIBLE before checking vcpu->kicked to + * avoid racing with kvm_pv_kick_cpu_op(). + */ + prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE); + + /* + * Somebody has already tried kicking us. Acknowledge that + * and terminate the wait. + */ + if (vcpu->kicked) { + vcpu->kicked = 0; + goto end_wait; + } + + /* Let's wait for either KVM_HC_KICK_CPU or someother event + * to wake us up. + */ + + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx); + schedule(); + vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu); + +end_wait: + finish_wait(&vcpu->wq, &wait); +} >>>> Having another hypercall to do yield/sleep (rather than effecting that >>>> via HLT) seems like an alternate clean solution here ..
WARNING: multiple messages have this Message-ID (diff)
From: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> To: Gleb Natapov <gleb@redhat.com> Cc: Jeremy Fitzhardinge <jeremy@goop.org>, KVM <kvm@vger.kernel.org>, linux-doc@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, Jan Kiszka <jan.kiszka@siemens.com>, Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>, Paul Mackerras <paulus@samba.org>, "H. Peter Anvin" <hpa@zytor.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>, Xen <xen-devel@lists.xensource.com>, Dave Jiang <dave.jiang@intel.com>, Glauber Costa <glommer@redhat.com>, X86 <x86@kernel.org>, Ingo Molnar <mingo@redhat.com>, Avi Kivity <avi@redhat.com>, Rik van Riel <riel@redhat.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Sasha Levin <levinsasha928@gmail.com>, Sedat Dilek <sedat.dilek@gmail.com>, Thomas Gleixner <tglx@linutronix.de>, Virtualization <virtualization@lists.linux-foundation.org>, Greg Kroah-Hartman <gregkh@suse.de>, LKML <linux-kernel@vger.kernel.org>, Dave Hansen <dave@linu> Subject: Re: [PATCH RFC V4 5/5] Documentation/kvm : Add documentation on Hypercalls and features used for PV spinlock Date: Tue, 17 Jan 2012 18:43:33 +0530 [thread overview] Message-ID: <4F1573FD.3030604@linux.vnet.ibm.com> (raw) In-Reply-To: <20120117125126.GQ2167@redhat.com> On 01/17/2012 06:21 PM, Gleb Natapov wrote: > On Tue, Jan 17, 2012 at 05:56:50PM +0530, Srivatsa Vaddagiri wrote: >> * Gleb Natapov<gleb@redhat.com> [2012-01-17 11:14:13]: >> >>>> The problem case I was thinking of was when guest VCPU would have issued >>>> HLT with interrupts disabled. I guess one option is to inject an NMI, >>>> and have the guest kernel NMI handler recognize this and make >>>> adjustments such that the vcpu avoids going back to HLT instruction. >>>> >>> Just kick vcpu out of a guest mode and adjust rip to point after HLT on >>> next re-entry. Don't forget to call vmx_clear_hlt(). >> >> Looks bit hackish to me compared to having another hypercall to yield! >> > Do not see anything hackish about it. But what you described above (the > part I replied to) is not another hypercall, but yet another NMI source > and special handling in a guest. So what hypercall do you mean? > Earlier version had a hypercall to sleep instead of current halt() approach. This was taken out to avoid extra hypercall. So here is the hypercall hunk referred : +/* + * kvm_pv_wait_for_kick_op : Block until kicked by either a KVM_HC_KICK_CPU + * hypercall or a event like interrupt. + * + * @vcpu : vcpu which is blocking. + */ +static void kvm_pv_wait_for_kick_op(struct kvm_vcpu *vcpu) +{ + DEFINE_WAIT(wait); + + /* + * Blocking on vcpu->wq allows us to wake up sooner if required to + * service pending events (like interrupts). + * + * Also set state to TASK_INTERRUPTIBLE before checking vcpu->kicked to + * avoid racing with kvm_pv_kick_cpu_op(). + */ + prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE); + + /* + * Somebody has already tried kicking us. Acknowledge that + * and terminate the wait. + */ + if (vcpu->kicked) { + vcpu->kicked = 0; + goto end_wait; + } + + /* Let's wait for either KVM_HC_KICK_CPU or someother event + * to wake us up. + */ + + srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx); + schedule(); + vcpu->srcu_idx = srcu_read_lock(&vcpu->kvm->srcu); + +end_wait: + finish_wait(&vcpu->wq, &wait); +} >>>> Having another hypercall to do yield/sleep (rather than effecting that >>>> via HLT) seems like an alternate clean solution here ..
next prev parent reply other threads:[~2012-01-17 13:13 UTC|newest] Thread overview: 139+ messages / expand[flat|nested] mbox.gz Atom feed top 2012-01-14 18:25 [PATCH RFC V4 0/5] kvm : Paravirt-spinlock support for KVM guests Raghavendra K T 2012-01-14 18:25 ` Raghavendra K T 2012-01-14 18:25 ` Raghavendra K T 2012-01-14 18:25 ` [PATCH RFC V4 1/5] debugfs: Add support to print u32 array in debugfs Raghavendra K T 2012-01-14 18:25 ` Raghavendra K T 2012-01-14 18:25 ` Raghavendra K T 2012-01-14 18:25 ` [PATCH RFC V4 2/5] kvm hypervisor : Add a hypercall to KVM hypervisor to support pv-ticketlocks Raghavendra K T 2012-01-14 18:25 ` Raghavendra K T 2012-01-14 18:25 ` Raghavendra K T 2012-01-16 3:24 ` Alexander Graf 2012-01-16 3:24 ` Alexander Graf 2012-01-16 8:43 ` Raghavendra K T 2012-01-16 8:43 ` Raghavendra K T 2012-01-16 9:03 ` Avi Kivity 2012-01-16 9:03 ` Avi Kivity 2012-01-16 9:55 ` Raghavendra K T 2012-01-16 9:55 ` Raghavendra K T 2012-01-14 18:26 ` [PATCH RFC V4 3/5] kvm guest : Added configuration support to enable debug information for KVM Guests Raghavendra K T 2012-01-14 18:26 ` Raghavendra K T 2012-01-14 18:26 ` Raghavendra K T 2012-01-14 18:26 ` [PATCH RFC V4 4/5] kvm : pv-ticketlocks support for linux guests running on KVM hypervisor Raghavendra K T 2012-01-14 18:26 ` Raghavendra K T 2012-01-14 18:26 ` Raghavendra K T 2012-01-16 3:12 ` Alexander Graf 2012-01-16 3:12 ` Alexander Graf 2012-01-16 7:25 ` Raghavendra K T 2012-01-16 7:25 ` Raghavendra K T 2012-01-16 9:05 ` Avi Kivity 2012-01-16 9:05 ` Avi Kivity 2012-01-16 14:13 ` Raghavendra K T 2012-01-16 14:13 ` Raghavendra K T 2012-01-16 14:47 ` Avi Kivity 2012-01-16 14:47 ` Avi Kivity 2012-01-16 23:49 ` Jeremy Fitzhardinge 2012-01-16 23:49 ` Jeremy Fitzhardinge 2012-01-17 11:02 ` Marcelo Tosatti 2012-01-17 11:02 ` Marcelo Tosatti 2012-01-17 11:33 ` Srivatsa Vaddagiri 2012-01-17 11:33 ` Srivatsa Vaddagiri 2012-01-18 1:34 ` Jeremy Fitzhardinge 2012-01-18 1:34 ` Jeremy Fitzhardinge 2012-01-18 13:54 ` Srivatsa Vaddagiri 2012-01-18 13:54 ` Srivatsa Vaddagiri 2012-01-18 21:52 ` Jeremy Fitzhardinge 2012-01-18 21:52 ` Jeremy Fitzhardinge 2012-01-24 14:08 ` Avi Kivity 2012-01-24 14:08 ` Avi Kivity 2012-01-24 18:51 ` Raghavendra K T 2012-01-24 18:51 ` Raghavendra K T 2012-01-17 18:57 ` Raghavendra K T 2012-01-17 18:57 ` Raghavendra K T 2012-01-24 19:01 ` Raghavendra K T 2012-01-14 18:27 ` [PATCH RFC V4 5/5] Documentation/kvm : Add documentation on Hypercalls and features used for PV spinlock Raghavendra K T 2012-01-14 18:27 ` Raghavendra K T 2012-01-14 18:27 ` Raghavendra K T 2012-01-14 18:27 ` Raghavendra K T 2012-01-16 3:23 ` Alexander Graf 2012-01-16 3:23 ` Alexander Graf 2012-01-16 3:51 ` Srivatsa Vaddagiri 2012-01-16 3:51 ` Srivatsa Vaddagiri 2012-01-16 4:00 ` Alexander Graf 2012-01-16 4:00 ` Alexander Graf 2012-01-16 8:47 ` Avi Kivity 2012-01-16 8:44 ` Raghavendra K T 2012-01-16 8:44 ` Raghavendra K T 2012-01-16 10:26 ` Alexander Graf 2012-01-16 10:26 ` Alexander Graf 2012-01-16 9:00 ` Avi Kivity 2012-01-16 9:00 ` Avi Kivity 2012-01-16 9:40 ` Srivatsa Vaddagiri 2012-01-16 10:14 ` Avi Kivity 2012-01-16 14:11 ` Srivatsa Vaddagiri 2012-01-17 9:14 ` Gleb Natapov 2012-01-17 9:14 ` Gleb Natapov 2012-01-17 12:26 ` Srivatsa Vaddagiri 2012-01-17 12:26 ` Srivatsa Vaddagiri 2012-01-17 12:51 ` Gleb Natapov 2012-01-17 12:51 ` Gleb Natapov 2012-01-17 13:11 ` Srivatsa Vaddagiri 2012-01-17 13:11 ` Srivatsa Vaddagiri 2012-01-17 13:20 ` Gleb Natapov 2012-01-17 13:20 ` Gleb Natapov 2012-01-17 14:28 ` Srivatsa Vaddagiri 2012-01-17 14:28 ` Srivatsa Vaddagiri 2012-01-17 15:32 ` Gleb Natapov 2012-01-17 15:32 ` Gleb Natapov 2012-01-17 15:53 ` Marcelo Tosatti 2012-01-17 15:53 ` Marcelo Tosatti 2012-01-20 15:09 ` Srivatsa Vaddagiri 2012-01-17 13:13 ` Raghavendra K T [this message] 2012-01-17 13:13 ` Raghavendra K T 2012-01-16 3:57 ` [PATCH RFC V4 0/5] kvm : Paravirt-spinlock support for KVM guests Alexander Graf 2012-01-16 3:57 ` Alexander Graf 2012-01-16 6:40 ` Jeremy Fitzhardinge 2012-01-16 6:40 ` Jeremy Fitzhardinge 2012-01-16 8:55 ` Avi Kivity 2012-01-16 8:55 ` Avi Kivity 2012-01-16 23:59 ` Jeremy Fitzhardinge 2012-01-16 23:59 ` Jeremy Fitzhardinge 2012-01-18 10:48 ` Raghavendra K T 2012-01-18 10:48 ` Raghavendra K T 2012-01-16 10:24 ` Alexander Graf 2012-01-16 10:24 ` Alexander Graf 2012-01-17 0:30 ` Jeremy Fitzhardinge 2012-01-17 0:30 ` Jeremy Fitzhardinge 2012-01-18 10:23 ` Raghavendra K T 2012-01-18 10:23 ` Raghavendra K T 2012-01-16 13:43 ` Raghavendra K T 2012-01-16 13:43 ` Raghavendra K T 2012-01-16 13:49 ` Avi Kivity 2012-01-16 13:49 ` Avi Kivity 2012-01-16 18:48 ` Raghavendra K T 2012-01-16 18:48 ` Raghavendra K T 2012-01-16 14:20 ` Srivatsa Vaddagiri 2012-01-16 14:20 ` Srivatsa Vaddagiri 2012-01-16 14:23 ` Alexander Graf 2012-01-16 14:23 ` Alexander Graf 2012-01-16 18:38 ` Raghavendra K T 2012-01-16 18:38 ` Raghavendra K T 2012-01-16 18:42 ` Alexander Graf 2012-01-16 18:42 ` Alexander Graf 2012-01-17 17:27 ` Raghavendra K T 2012-01-17 17:27 ` Raghavendra K T 2012-01-17 17:39 ` Alexander Graf 2012-01-17 17:39 ` Alexander Graf 2012-01-17 18:36 ` Raghavendra K T 2012-01-17 18:36 ` Raghavendra K T 2012-01-17 21:57 ` Dave Hansen 2012-01-17 21:57 ` Dave Hansen 2012-01-18 2:27 ` Raghavendra K T 2012-01-18 2:27 ` Raghavendra K T 2012-01-25 8:55 ` Raghavendra K T 2012-01-25 8:55 ` Raghavendra K T 2012-01-25 16:35 ` Konrad Rzeszutek Wilk 2012-01-25 16:35 ` Konrad Rzeszutek Wilk 2012-01-25 17:45 ` Raghavendra K T 2012-01-25 17:45 ` Raghavendra K T 2012-01-25 19:05 ` Konrad Rzeszutek Wilk 2012-01-25 19:05 ` Konrad Rzeszutek Wilk
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