From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH 2/6 V2] Add functions to check if the host has stopped the vm Date: Tue, 01 Nov 2011 14:28:31 -0500 Message-ID: <4EB0485F.8010406@us.ibm.com> References: <1320091650-24682-1-git-send-email-emunson@mgebm.net> <1320091650-24682-3-git-send-email-emunson@mgebm.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1320091650-24682-3-git-send-email-emunson@mgebm.net> Sender: linux-kernel-owner@vger.kernel.org To: Eric B Munson Cc: avi@redhat.com, mingo@redhat.com, x86@kernel.org, hpa@zytor.com, arnd@arndb.de, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-arch@vger.kernel.org, ryanh@linux.vnet.ibm.com List-Id: linux-arch.vger.kernel.org On 10/31/2011 03:07 PM, Eric B Munson wrote: > When a host stops or suspends a VM it will set a flag to show this. The > watchdog will use these functions to determine if a softlockup is real, or the > result of a suspended VM. > > Signed-off-by: Eric B Munson > --- > arch/x86/include/asm/pvclock.h | 2 ++ > arch/x86/kernel/kvmclock.c | 19 +++++++++++++++++++ > 2 files changed, 21 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h > index c59cc97..7d3ba41 100644 > --- a/arch/x86/include/asm/pvclock.h > +++ b/arch/x86/include/asm/pvclock.h > @@ -13,6 +13,8 @@ void pvclock_read_wallclock(struct pvclock_wall_clock *wall, > struct timespec *ts); > void pvclock_resume(void); > > +bool kvm_check_and_clear_host_stopped(int cpu); A kvm-specific function shouldn't be declared in pvclock.h as this is shared code between KVM and Xen. > + > /* > * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction, > * yielding a 64-bit result. > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c > index c1a0188..8ddcfaf 100644 > --- a/arch/x86/kernel/kvmclock.c > +++ b/arch/x86/kernel/kvmclock.c > @@ -113,6 +113,25 @@ static void kvm_get_preset_lpj(void) > preset_lpj = lpj; > } > > +bool kvm_check_and_clear_host_stopped(int cpu) > +{ > + bool ret = false; > + struct pvclock_vcpu_time_info *src; > + > + /* > + * per_cpu() is safe here because this function is only called from > + * timer functions where preemption is already disabled. > + */ > + WARN_ON(!in_atomic()); > + src =&per_cpu(hv_clock, cpu); > + if ((src->flags& PVCLOCK_GUEST_STOPPED) != 0) { > + src->flags = src->flags& (~PVCLOCK_GUEST_STOPPED); > + ret = true; > + } It would be helpful to separate out the patches for guest enablement from host enablement. This is a guest function, correct? Don't you need an atomic getandset here? Can the host clear this flag or only set it? It's ashame we don't have a proper pvclock spec in Documentation/. I would suggest at least adding a description of how this bit works in the first patch. Regards, Anthony Liguori > + > + return ret; > +} > + > static struct clocksource kvm_clock = { > .name = "kvm-clock", > .read = kvm_clock_get_cycles, From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e3.ny.us.ibm.com ([32.97.182.143]:45709 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750900Ab1KATbB (ORCPT ); Tue, 1 Nov 2011 15:31:01 -0400 Received: from /spool/local by e3.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 1 Nov 2011 15:29:19 -0400 Message-ID: <4EB0485F.8010406@us.ibm.com> Date: Tue, 01 Nov 2011 14:28:31 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [PATCH 2/6 V2] Add functions to check if the host has stopped the vm References: <1320091650-24682-1-git-send-email-emunson@mgebm.net> <1320091650-24682-3-git-send-email-emunson@mgebm.net> In-Reply-To: <1320091650-24682-3-git-send-email-emunson@mgebm.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Eric B Munson Cc: avi@redhat.com, mingo@redhat.com, x86@kernel.org, hpa@zytor.com, arnd@arndb.de, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-arch@vger.kernel.org, ryanh@linux.vnet.ibm.com Message-ID: <20111101192831.Hw5MGX4McyroLf8oAPx-7YxhLAVVpGdKTS3VRCsd3ow@z> On 10/31/2011 03:07 PM, Eric B Munson wrote: > When a host stops or suspends a VM it will set a flag to show this. The > watchdog will use these functions to determine if a softlockup is real, or the > result of a suspended VM. > > Signed-off-by: Eric B Munson > --- > arch/x86/include/asm/pvclock.h | 2 ++ > arch/x86/kernel/kvmclock.c | 19 +++++++++++++++++++ > 2 files changed, 21 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h > index c59cc97..7d3ba41 100644 > --- a/arch/x86/include/asm/pvclock.h > +++ b/arch/x86/include/asm/pvclock.h > @@ -13,6 +13,8 @@ void pvclock_read_wallclock(struct pvclock_wall_clock *wall, > struct timespec *ts); > void pvclock_resume(void); > > +bool kvm_check_and_clear_host_stopped(int cpu); A kvm-specific function shouldn't be declared in pvclock.h as this is shared code between KVM and Xen. > + > /* > * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction, > * yielding a 64-bit result. > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c > index c1a0188..8ddcfaf 100644 > --- a/arch/x86/kernel/kvmclock.c > +++ b/arch/x86/kernel/kvmclock.c > @@ -113,6 +113,25 @@ static void kvm_get_preset_lpj(void) > preset_lpj = lpj; > } > > +bool kvm_check_and_clear_host_stopped(int cpu) > +{ > + bool ret = false; > + struct pvclock_vcpu_time_info *src; > + > + /* > + * per_cpu() is safe here because this function is only called from > + * timer functions where preemption is already disabled. > + */ > + WARN_ON(!in_atomic()); > + src =&per_cpu(hv_clock, cpu); > + if ((src->flags& PVCLOCK_GUEST_STOPPED) != 0) { > + src->flags = src->flags& (~PVCLOCK_GUEST_STOPPED); > + ret = true; > + } It would be helpful to separate out the patches for guest enablement from host enablement. This is a guest function, correct? Don't you need an atomic getandset here? Can the host clear this flag or only set it? It's ashame we don't have a proper pvclock spec in Documentation/. I would suggest at least adding a description of how this bit works in the first patch. Regards, Anthony Liguori > + > + return ret; > +} > + > static struct clocksource kvm_clock = { > .name = "kvm-clock", > .read = kvm_clock_get_cycles,