| Message ID | 20190604122404.GA18979@amt.cnet (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | None | expand |
On 6/4/19 1:24 PM, Marcelo Tosatti wrote: > > When performing guest side polling, it is not necessary to > also perform host side polling. > > So disable host side polling, via the new MSR interface, > when loading cpuidle-haltpoll driver. > > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> > > --- > > v2: remove extra "}" > > arch/x86/Kconfig | 7 +++++ > arch/x86/include/asm/cpuidle_haltpoll.h | 8 ++++++ > arch/x86/kernel/kvm.c | 40 ++++++++++++++++++++++++++++++++ > drivers/cpuidle/cpuidle-haltpoll.c | 9 ++++++- > include/linux/cpuidle_haltpoll.h | 16 ++++++++++++ > 5 files changed, 79 insertions(+), 1 deletion(-) > > Index: linux-2.6.git/arch/x86/include/asm/cpuidle_haltpoll.h > =================================================================== > --- /dev/null 1970-01-01 00:00:00.000000000 +0000 > +++ linux-2.6.git/arch/x86/include/asm/cpuidle_haltpoll.h 2019-06-03 19:38:42.328718617 -0300 > @@ -0,0 +1,8 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef _ARCH_HALTPOLL_H > +#define _ARCH_HALTPOLL_H > + > +void arch_haltpoll_enable(void); > +void arch_haltpoll_disable(void); > + > +#endif > Index: linux-2.6.git/drivers/cpuidle/cpuidle-haltpoll.c > =================================================================== > --- linux-2.6.git.orig/drivers/cpuidle/cpuidle-haltpoll.c 2019-06-03 19:38:12.376619124 -0300 > +++ linux-2.6.git/drivers/cpuidle/cpuidle-haltpoll.c 2019-06-03 19:38:42.328718617 -0300 > @@ -15,6 +15,7 @@ > #include <linux/module.h> > #include <linux/timekeeping.h> > #include <linux/sched/idle.h> > +#include <linux/cpuidle_haltpoll.h> > #define CREATE_TRACE_POINTS > #include "cpuidle-haltpoll-trace.h" > > @@ -157,11 +158,17 @@ > > static int __init haltpoll_init(void) > { > - return cpuidle_register(&haltpoll_driver, NULL); > + int ret = cpuidle_register(&haltpoll_driver, NULL); > + > + if (ret == 0) > + arch_haltpoll_enable(); > + > + return ret; > } > > static void __exit haltpoll_exit(void) > { > + arch_haltpoll_disable(); > cpuidle_unregister(&haltpoll_driver); > } > > Index: linux-2.6.git/include/linux/cpuidle_haltpoll.h > =================================================================== > --- /dev/null 1970-01-01 00:00:00.000000000 +0000 > +++ linux-2.6.git/include/linux/cpuidle_haltpoll.h 2019-06-03 19:41:57.293366260 -0300 > @@ -0,0 +1,16 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +#ifndef _CPUIDLE_HALTPOLL_H > +#define _CPUIDLE_HALTPOLL_H > + > +#ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL > +#include <asm/cpuidle_haltpoll.h> > +#else > +static inline void arch_haltpoll_enable(void) > +{ > +} > + > +static inline void arch_haltpoll_disable(void) > +{ > +} > +#endif > +#endif > Index: linux-2.6.git/arch/x86/Kconfig > =================================================================== > --- linux-2.6.git.orig/arch/x86/Kconfig 2019-06-03 19:38:12.376619124 -0300 > +++ linux-2.6.git/arch/x86/Kconfig 2019-06-03 19:42:34.478489868 -0300 > @@ -787,6 +787,7 @@ > bool "KVM Guest support (including kvmclock)" > depends on PARAVIRT > select PARAVIRT_CLOCK > + select ARCH_CPUIDLE_HALTPOLL > default y > ---help--- > This option enables various optimizations for running under the KVM > @@ -795,6 +796,12 @@ > underlying device model, the host provides the guest with > timing infrastructure such as time of day, and system time > > +config ARCH_CPUIDLE_HALTPOLL > + def_bool n > + proUmpt "Disable host haltpoll when loading haltpoll driver" > + help > + If virtualized under KVM, disable host haltpoll. > + > config PVH > bool "Support for running PVH guests" > ---help--- > Index: linux-2.6.git/arch/x86/kernel/kvm.c > =================================================================== > --- linux-2.6.git.orig/arch/x86/kernel/kvm.c 2019-06-03 19:38:12.376619124 -0300 > +++ linux-2.6.git/arch/x86/kernel/kvm.c 2019-06-03 19:40:14.359024312 -0300 > @@ -853,3 +853,43 @@ > } > > #endif /* CONFIG_PARAVIRT_SPINLOCKS */ > + > +#ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL > + > +void kvm_disable_host_haltpoll(void *i) > +{ > + wrmsrl(MSR_KVM_POLL_CONTROL, 0); > +} > + > +void kvm_enable_host_haltpoll(void *i) > +{ > + wrmsrl(MSR_KVM_POLL_CONTROL, 1); > +} > + > +void arch_haltpoll_enable(void) > +{ > + if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) > + return; > + Perhaps warn the user when failing to disable host poll e.g.: if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) { pr_warn_once("haltpoll: Failed to disable host halt polling\n"); return; } But I wonder whether we should fail to load cpuidle-haltpoll when host halt polling can't be disabled[*]? That is to avoid polling in both host and guest and *possibly* avoid chances for performance regressions when running on older hypervisors? [*] with guest still able load with lack of host polling control via modparam > + preempt_disable(); > + /* Enabling guest halt poll disables host halt poll */ > + kvm_disable_host_haltpoll(NULL); > + smp_call_function(kvm_disable_host_haltpoll, NULL, 1); > + preempt_enable(); > +} > +EXPORT_SYMBOL_GPL(arch_haltpoll_enable); > + > +void arch_haltpoll_disable(void) > +{ > + if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) > + return; > + > + preempt_disable(); > + /* Enabling guest halt poll disables host halt poll */ > + kvm_enable_host_haltpoll(NULL); > + smp_call_function(kvm_enable_host_haltpoll, NULL, 1); > + preempt_enable(); > +} > + > +EXPORT_SYMBOL_GPL(arch_haltpoll_disable); > +#endif >
Hello, On Thu, Jun 06, 2019 at 07:25:28PM +0100, Joao Martins wrote: > But I wonder whether we should fail to load cpuidle-haltpoll when host halt > polling can't be disabled[*]? That is to avoid polling in both host and guest > and *possibly* avoid chances for performance regressions when running on older > hypervisors? I don't think it's necessary: that would force an upgrade of the host KVM version in order to use the guest haltpoll feature with an upgraded guest kernel that can use the guest haltpoll. The guest haltpoll is self contained in the guest, so there's no reason to prevent that by design or to force upgrade of the KVM host version. It'd be more than enough to reload kvm.ko in the host with the host haltpoll set to zero with the module parameter already available, to achieve the same runtime without requiring a forced host upgrade. The warning however sounds sensible. Thanks, Andrea
On 6/6/19 7:36 PM, Andrea Arcangeli wrote: > Hello, > > On Thu, Jun 06, 2019 at 07:25:28PM +0100, Joao Martins wrote: >> But I wonder whether we should fail to load cpuidle-haltpoll when host halt >> polling can't be disabled[*]? That is to avoid polling in both host and guest >> and *possibly* avoid chances for performance regressions when running on older >> hypervisors? > > I don't think it's necessary: that would force an upgrade of the host > KVM version in order to use the guest haltpoll feature with an > upgraded guest kernel that can use the guest haltpoll. > Hence why I was suggesting a *guest* cpuidle-haltpoll module parameter to still allow it to load or otherwise (or allow guest to pick). > The guest haltpoll is self contained in the guest, so there's no > reason to prevent that by design or to force upgrade of the KVM host > version. It'd be more than enough to reload kvm.ko in the host with > the host haltpoll set to zero with the module parameter already > available, to achieve the same runtime without requiring a forced host > upgrade. > It's just with the new driver we unilaterally poll on both sides, just felt I would point it out should this raise unattended performance side effects ;) > The warning however sounds sensible. > Cool. Joao
On 6/6/19 7:51 PM, Joao Martins wrote: > On 6/6/19 7:36 PM, Andrea Arcangeli wrote: >> Hello, >> >> On Thu, Jun 06, 2019 at 07:25:28PM +0100, Joao Martins wrote: >>> But I wonder whether we should fail to load cpuidle-haltpoll when host halt >>> polling can't be disabled[*]? That is to avoid polling in both host and guest >>> and *possibly* avoid chances for performance regressions when running on older >>> hypervisors? >> >> I don't think it's necessary: that would force an upgrade of the host >> KVM version in order to use the guest haltpoll feature with an >> upgraded guest kernel that can use the guest haltpoll. >> > Hence why I was suggesting a *guest* cpuidle-haltpoll module parameter to still > allow it to load or otherwise (or allow guest to pick). > By 'still allow it to load', I meant specifically to handle the case when host polling control is not supported and what to do in that case. >> The guest haltpoll is self contained in the guest, so there's no >> reason to prevent that by design or to force upgrade of the KVM host >> version. It'd be more than enough to reload kvm.ko in the host with >> the host haltpoll set to zero with the module parameter already >> available, to achieve the same runtime without requiring a forced host >> upgrade. >> > It's just with the new driver we unilaterally poll on both sides, just felt I > would point it out should this raise unattended performance side effects ;) > To be clear: by 'unilaterally' I was trying to refer to hosts KVM without polling control (which is safe to say that it is the majority atm?). Alternatively, there's always the option that if guest sees any issues on that case (with polling on both sides=, that it can always blacklist cpuidle-haltpoll. But may this is not an issue and perhaps majority of users still observes benefit when polling is enabled on guest and host. >> The warning however sounds sensible. >> > > Cool. > > Joao >
On Thu, Jun 06, 2019 at 08:22:40PM +0100, Joao Martins wrote: > On 6/6/19 7:51 PM, Joao Martins wrote: > > On 6/6/19 7:36 PM, Andrea Arcangeli wrote: > >> Hello, > >> > >> On Thu, Jun 06, 2019 at 07:25:28PM +0100, Joao Martins wrote: > >>> But I wonder whether we should fail to load cpuidle-haltpoll when host halt > >>> polling can't be disabled[*]? That is to avoid polling in both host and guest > >>> and *possibly* avoid chances for performance regressions when running on older > >>> hypervisors? > >> > >> I don't think it's necessary: that would force an upgrade of the host > >> KVM version in order to use the guest haltpoll feature with an > >> upgraded guest kernel that can use the guest haltpoll. > >> > > Hence why I was suggesting a *guest* cpuidle-haltpoll module parameter to still > > allow it to load or otherwise (or allow guest to pick). > > > By 'still allow it to load', I meant specifically to handle the case when host > polling control is not supported and what to do in that case. All right, we could add a force=1 parameter to force loading as an opt-in (and fail load by default with force=0). > >> The guest haltpoll is self contained in the guest, so there's no > >> reason to prevent that by design or to force upgrade of the KVM host > >> version. It'd be more than enough to reload kvm.ko in the host with > >> the host haltpoll set to zero with the module parameter already > >> available, to achieve the same runtime without requiring a forced host > >> upgrade. > >> > > It's just with the new driver we unilaterally poll on both sides, just felt I > > would point it out should this raise unattended performance side effects ;) > > > To be clear: by 'unilaterally' I was trying to refer to hosts KVM without > polling control (which is safe to say that it is the majority atm?). > > Alternatively, there's always the option that if guest sees any issues on that > case (with polling on both sides=, that it can always blacklist > cpuidle-haltpoll. But may this is not an issue and perhaps majority of users > still observes benefit when polling is enabled on guest and host. It should be workload dependent if it increases performance to haltpoll both in both host kernel and guest, the only sure cons is that it'd burn some more energy.. By default the cpuidle-haltpoll driver shouldn't get loaded if it's built as a module (the expectation is the default will be =m), and it can still easily disabled with rmmod if it hurts performance. So the policy if to activate guest haltpoll or not will still reside in the guest userland: the guest userland code or guest admin, without a force parameter has to decide if to load or not to load the module, with the force=1 parameter it'll have to decide if to load it with =0 or =1 (or load it first with =0 and then decide if to try to load it again with =1 which would be the benefit the force parameter provides). To decide if to load or not to load it, the guest userland could check if there's no support for disabling the host haltpoll, which can be verified with rdmsr too. # rdmsr 0x4b564d05 rdmsr: CPU 0 cannot read MSR 0x4b564d05 Adding a force=1 parameter to force loading will just add a few lines more of kernel code, I'm neutral on that but it looks fine either ways. Thanks, Andrea
Hi Joao, On Thu, Jun 06, 2019 at 07:25:28PM +0100, Joao Martins wrote: > On 6/4/19 1:24 PM, Marcelo Tosatti wrote: > > > > When performing guest side polling, it is not necessary to > > also perform host side polling. > > > > So disable host side polling, via the new MSR interface, > > when loading cpuidle-haltpoll driver. > > > > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> > > > > --- > > > > v2: remove extra "}" > > > > arch/x86/Kconfig | 7 +++++ > > arch/x86/include/asm/cpuidle_haltpoll.h | 8 ++++++ > > arch/x86/kernel/kvm.c | 40 ++++++++++++++++++++++++++++++++ > > drivers/cpuidle/cpuidle-haltpoll.c | 9 ++++++- > > include/linux/cpuidle_haltpoll.h | 16 ++++++++++++ > > 5 files changed, 79 insertions(+), 1 deletion(-) > > > > Index: linux-2.6.git/arch/x86/include/asm/cpuidle_haltpoll.h > > =================================================================== > > --- /dev/null 1970-01-01 00:00:00.000000000 +0000 > > +++ linux-2.6.git/arch/x86/include/asm/cpuidle_haltpoll.h 2019-06-03 19:38:42.328718617 -0300 > > @@ -0,0 +1,8 @@ > > +/* SPDX-License-Identifier: GPL-2.0 */ > > +#ifndef _ARCH_HALTPOLL_H > > +#define _ARCH_HALTPOLL_H > > + > > +void arch_haltpoll_enable(void); > > +void arch_haltpoll_disable(void); > > + > > +#endif > > Index: linux-2.6.git/drivers/cpuidle/cpuidle-haltpoll.c > > =================================================================== > > --- linux-2.6.git.orig/drivers/cpuidle/cpuidle-haltpoll.c 2019-06-03 19:38:12.376619124 -0300 > > +++ linux-2.6.git/drivers/cpuidle/cpuidle-haltpoll.c 2019-06-03 19:38:42.328718617 -0300 > > @@ -15,6 +15,7 @@ > > #include <linux/module.h> > > #include <linux/timekeeping.h> > > #include <linux/sched/idle.h> > > +#include <linux/cpuidle_haltpoll.h> > > #define CREATE_TRACE_POINTS > > #include "cpuidle-haltpoll-trace.h" > > > > @@ -157,11 +158,17 @@ > > > > static int __init haltpoll_init(void) > > { > > - return cpuidle_register(&haltpoll_driver, NULL); > > + int ret = cpuidle_register(&haltpoll_driver, NULL); > > + > > + if (ret == 0) > > + arch_haltpoll_enable(); > > + > > + return ret; > > } > > > > static void __exit haltpoll_exit(void) > > { > > + arch_haltpoll_disable(); > > cpuidle_unregister(&haltpoll_driver); > > } > > > > Index: linux-2.6.git/include/linux/cpuidle_haltpoll.h > > =================================================================== > > --- /dev/null 1970-01-01 00:00:00.000000000 +0000 > > +++ linux-2.6.git/include/linux/cpuidle_haltpoll.h 2019-06-03 19:41:57.293366260 -0300 > > @@ -0,0 +1,16 @@ > > +/* SPDX-License-Identifier: GPL-2.0 */ > > +#ifndef _CPUIDLE_HALTPOLL_H > > +#define _CPUIDLE_HALTPOLL_H > > + > > +#ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL > > +#include <asm/cpuidle_haltpoll.h> > > +#else > > +static inline void arch_haltpoll_enable(void) > > +{ > > +} > > + > > +static inline void arch_haltpoll_disable(void) > > +{ > > +} > > +#endif > > +#endif > > Index: linux-2.6.git/arch/x86/Kconfig > > =================================================================== > > --- linux-2.6.git.orig/arch/x86/Kconfig 2019-06-03 19:38:12.376619124 -0300 > > +++ linux-2.6.git/arch/x86/Kconfig 2019-06-03 19:42:34.478489868 -0300 > > @@ -787,6 +787,7 @@ > > bool "KVM Guest support (including kvmclock)" > > depends on PARAVIRT > > select PARAVIRT_CLOCK > > + select ARCH_CPUIDLE_HALTPOLL > > default y > > ---help--- > > This option enables various optimizations for running under the KVM > > @@ -795,6 +796,12 @@ > > underlying device model, the host provides the guest with > > timing infrastructure such as time of day, and system time > > > > +config ARCH_CPUIDLE_HALTPOLL > > + def_bool n > > + proUmpt "Disable host haltpoll when loading haltpoll driver" > > + help > > + If virtualized under KVM, disable host haltpoll. > > + > > config PVH > > bool "Support for running PVH guests" > > ---help--- > > Index: linux-2.6.git/arch/x86/kernel/kvm.c > > =================================================================== > > --- linux-2.6.git.orig/arch/x86/kernel/kvm.c 2019-06-03 19:38:12.376619124 -0300 > > +++ linux-2.6.git/arch/x86/kernel/kvm.c 2019-06-03 19:40:14.359024312 -0300 > > @@ -853,3 +853,43 @@ > > } > > > > #endif /* CONFIG_PARAVIRT_SPINLOCKS */ > > + > > +#ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL > > + > > +void kvm_disable_host_haltpoll(void *i) > > +{ > > + wrmsrl(MSR_KVM_POLL_CONTROL, 0); > > +} > > + > > +void kvm_enable_host_haltpoll(void *i) > > +{ > > + wrmsrl(MSR_KVM_POLL_CONTROL, 1); > > +} > > + > > +void arch_haltpoll_enable(void) > > +{ > > + if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) > > + return; > > + > > Perhaps warn the user when failing to disable host poll e.g.: > > if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) { > pr_warn_once("haltpoll: Failed to disable host halt polling\n"); > return; > } > > But I wonder whether we should fail to load cpuidle-haltpoll when host halt > polling can't be disabled[*]? That is to avoid polling in both host and guest > and *possibly* avoid chances for performance regressions when running on older > hypervisors? > > [*] with guest still able load with lack of host polling control via modparam I don't think so. First, the driver reduces the halt poll interval when the system is idle, so overhead is reduced to zero in such cases. Moreover, when both host and guest side polling are performed, power might be wasted, but i haven't seen a significant performance regression caused by it. Thanks. > > > + preempt_disable(); > > + /* Enabling guest halt poll disables host halt poll */ > > + kvm_disable_host_haltpoll(NULL); > > + smp_call_function(kvm_disable_host_haltpoll, NULL, 1); > > + preempt_enable(); > > +} > > +EXPORT_SYMBOL_GPL(arch_haltpoll_enable); > > + > > +void arch_haltpoll_disable(void) > > +{ > > + if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) > > + return; > > + > > + preempt_disable(); > > + /* Enabling guest halt poll disables host halt poll */ > > + kvm_enable_host_haltpoll(NULL); > > + smp_call_function(kvm_enable_host_haltpoll, NULL, 1); > > + preempt_enable(); > > +} > > + > > +EXPORT_SYMBOL_GPL(arch_haltpoll_disable); > > +#endif > >
On Thu, Jun 06, 2019 at 02:36:32PM -0400, Andrea Arcangeli wrote: > Hello, > > On Thu, Jun 06, 2019 at 07:25:28PM +0100, Joao Martins wrote: > > But I wonder whether we should fail to load cpuidle-haltpoll when host halt > > polling can't be disabled[*]? That is to avoid polling in both host and guest > > and *possibly* avoid chances for performance regressions when running on older > > hypervisors? > > I don't think it's necessary: that would force an upgrade of the host > KVM version in order to use the guest haltpoll feature with an > upgraded guest kernel that can use the guest haltpoll. > > The guest haltpoll is self contained in the guest, so there's no > reason to prevent that by design or to force upgrade of the KVM host > version. It'd be more than enough to reload kvm.ko in the host with > the host haltpoll set to zero with the module parameter already > available, to achieve the same runtime without requiring a forced host > upgrade. > > The warning however sounds sensible. Alright, added a warning: void arch_haltpoll_enable(void) { if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) { WARN_ONCE(1, "kvm: host does not support poll control, can't " "disable host polling (host upgrade " " recommended).\n" return; } Thanks
Index: linux-2.6.git/arch/x86/include/asm/cpuidle_haltpoll.h =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-2.6.git/arch/x86/include/asm/cpuidle_haltpoll.h 2019-06-03 19:38:42.328718617 -0300 @@ -0,0 +1,8 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ARCH_HALTPOLL_H +#define _ARCH_HALTPOLL_H + +void arch_haltpoll_enable(void); +void arch_haltpoll_disable(void); + +#endif Index: linux-2.6.git/drivers/cpuidle/cpuidle-haltpoll.c =================================================================== --- linux-2.6.git.orig/drivers/cpuidle/cpuidle-haltpoll.c 2019-06-03 19:38:12.376619124 -0300 +++ linux-2.6.git/drivers/cpuidle/cpuidle-haltpoll.c 2019-06-03 19:38:42.328718617 -0300 @@ -15,6 +15,7 @@ #include <linux/module.h> #include <linux/timekeeping.h> #include <linux/sched/idle.h> +#include <linux/cpuidle_haltpoll.h> #define CREATE_TRACE_POINTS #include "cpuidle-haltpoll-trace.h" @@ -157,11 +158,17 @@ static int __init haltpoll_init(void) { - return cpuidle_register(&haltpoll_driver, NULL); + int ret = cpuidle_register(&haltpoll_driver, NULL); + + if (ret == 0) + arch_haltpoll_enable(); + + return ret; } static void __exit haltpoll_exit(void) { + arch_haltpoll_disable(); cpuidle_unregister(&haltpoll_driver); } Index: linux-2.6.git/include/linux/cpuidle_haltpoll.h =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux-2.6.git/include/linux/cpuidle_haltpoll.h 2019-06-03 19:41:57.293366260 -0300 @@ -0,0 +1,16 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _CPUIDLE_HALTPOLL_H +#define _CPUIDLE_HALTPOLL_H + +#ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL +#include <asm/cpuidle_haltpoll.h> +#else +static inline void arch_haltpoll_enable(void) +{ +} + +static inline void arch_haltpoll_disable(void) +{ +} +#endif +#endif Index: linux-2.6.git/arch/x86/Kconfig =================================================================== --- linux-2.6.git.orig/arch/x86/Kconfig 2019-06-03 19:38:12.376619124 -0300 +++ linux-2.6.git/arch/x86/Kconfig 2019-06-03 19:42:34.478489868 -0300 @@ -787,6 +787,7 @@ bool "KVM Guest support (including kvmclock)" depends on PARAVIRT select PARAVIRT_CLOCK + select ARCH_CPUIDLE_HALTPOLL default y ---help--- This option enables various optimizations for running under the KVM @@ -795,6 +796,12 @@ underlying device model, the host provides the guest with timing infrastructure such as time of day, and system time +config ARCH_CPUIDLE_HALTPOLL + def_bool n + prompt "Disable host haltpoll when loading haltpoll driver" + help + If virtualized under KVM, disable host haltpoll. + config PVH bool "Support for running PVH guests" ---help--- Index: linux-2.6.git/arch/x86/kernel/kvm.c =================================================================== --- linux-2.6.git.orig/arch/x86/kernel/kvm.c 2019-06-03 19:38:12.376619124 -0300 +++ linux-2.6.git/arch/x86/kernel/kvm.c 2019-06-03 19:40:14.359024312 -0300 @@ -853,3 +853,43 @@ } #endif /* CONFIG_PARAVIRT_SPINLOCKS */ + +#ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL + +void kvm_disable_host_haltpoll(void *i) +{ + wrmsrl(MSR_KVM_POLL_CONTROL, 0); +} + +void kvm_enable_host_haltpoll(void *i) +{ + wrmsrl(MSR_KVM_POLL_CONTROL, 1); +} + +void arch_haltpoll_enable(void) +{ + if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) + return; + + preempt_disable(); + /* Enabling guest halt poll disables host halt poll */ + kvm_disable_host_haltpoll(NULL); + smp_call_function(kvm_disable_host_haltpoll, NULL, 1); + preempt_enable(); +} +EXPORT_SYMBOL_GPL(arch_haltpoll_enable); + +void arch_haltpoll_disable(void) +{ + if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) + return; + + preempt_disable(); + /* Enabling guest halt poll disables host halt poll */ + kvm_enable_host_haltpoll(NULL); + smp_call_function(kvm_enable_host_haltpoll, NULL, 1); + preempt_enable(); +} + +EXPORT_SYMBOL_GPL(arch_haltpoll_disable); +#endif
When performing guest side polling, it is not necessary to also perform host side polling. So disable host side polling, via the new MSR interface, when loading cpuidle-haltpoll driver. Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> --- v2: remove extra "}" arch/x86/Kconfig | 7 +++++ arch/x86/include/asm/cpuidle_haltpoll.h | 8 ++++++ arch/x86/kernel/kvm.c | 40 ++++++++++++++++++++++++++++++++ drivers/cpuidle/cpuidle-haltpoll.c | 9 ++++++- include/linux/cpuidle_haltpoll.h | 16 ++++++++++++ 5 files changed, 79 insertions(+), 1 deletion(-)