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[PATCH RFC V6 0/5] kvm : Paravirt-spinlock support for KVM guests

 

 

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raghavendra.kt at linux

Apr 23, 2012, 2:59 AM

Post #1 of 1 (56 views)
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[PATCH RFC V6 0/5] kvm : Paravirt-spinlock support for KVM guests

The 5-patch series to follow this email extends KVM-hypervisor and Linux guest
running on KVM-hypervisor to support pv-ticket spinlocks, based on Xen's
implementation.

One hypercall is introduced in KVM hypervisor,that allows a vcpu to kick
another vcpu out of halt state.
The blocking of vcpu is done using halt() in (lock_spinning) slowpath.

Note: 1) patch is based on 3.4-rc3 + ticketlock patches in
https://lkml.org/lkml/2012/4/19/335

[ The patches are targeted for 3.5 window ]

Changes in V6:
- Rebased to 3.4-rc3
- Removed debugfs changes patch which should now be in Xen/linux-next.
(https://lkml.org/lkml/2012/3/30/687)
- Removed PV_UNHALT_MSR since currently we don't need guest communication,
and made pv_unhalt folded to GET_MP_STATE (Marcello, Avi[long back])
- Take jumplabel changes from Ingo/Jason into use (static_key_slow_inc usage)
- Added inline to spinlock_init in non PARAVIRT case
- Move arch specific code to arch/x86 and add stubs to other archs (Marcello)
- Added more comments on pv_unhalt usage etc (Marcello)

Changes in V5:
- rebased to 3.3-rc6
- added PV_UNHALT_MSR that would help in live migration (Avi)
- removed PV_LOCK_KICK vcpu request and pv_unhalt flag (re)added.
- Changed hypercall documentaion (Alex).
- mode_t changed to umode_t in debugfs.
- MSR related documentation added.
- rename PV_LOCK_KICK to PV_UNHALT.
- host and guest patches not mixed. (Marcelo, Alex)
- kvm_kick_cpu now takes cpu so it can be used by flush_tlb_ipi_other
paravirtualization (Nikunj)
- coding style changes in variable declarion etc (Srikar)

Changes in V4:
- reabsed to 3.2.0 pre.
- use APIC ID for kicking the vcpu and use kvm_apic_match_dest for matching (Avi)
- fold vcpu->kicked flag into vcpu->requests (KVM_REQ_PVLOCK_KICK) and related
changes for UNHALT path to make pv ticket spinlock migration friendly(Avi, Marcello)
- Added Documentation for CPUID, Hypercall (KVM_HC_KICK_CPU)
and capabilty (KVM_CAP_PVLOCK_KICK) (Avi)
- Remove unneeded kvm_arch_vcpu_ioctl_set_mpstate call. (Marcello)
- cumulative variable type changed (int ==> u32) in add_stat (Konrad)
- remove unneeded kvm_guest_init for !CONFIG_KVM_GUEST case

Changes in V3:
- rebased to 3.2-rc1
- use halt() instead of wait for kick hypercall.
- modify kick hyper call to do wakeup halted vcpu.
- hook kvm_spinlock_init to smp_prepare_cpus call (moved the call out of head##.c).
- fix the potential race when zero_stat is read.
- export debugfs_create_32 and add documentation to API.
- use static inline and enum instead of ADDSTAT macro.
- add barrier() in after setting kick_vcpu.
- empty static inline function for kvm_spinlock_init.
- combine the patches one and two readuce overhead.
- make KVM_DEBUGFS depends on DEBUGFS.
- include debugfs header unconditionally.

Changes in V2:
- rebased patchesto -rc9
- synchronization related changes based on Jeremy's changes
(Jeremy Fitzhardinge <jeremy.fitzhardinge [at] citrix>) pointed by
Stephan Diestelhorst <stephan.diestelhorst [at] amd>
- enabling 32 bit guests
- splitted patches into two more chunks

Results:
results for PLE / non PLE machine were posted for V5 patches in
https://lkml.org/lkml/2012/3/23/50
https://lkml.org/lkml/2012/4/5/73

Current series is giving similar results but more formal results will
be posted in next couple of days.

Interestingly with current patchset I do not see CPU stalls observed in vanilla.

TODO: 1) remove CONFIG_PARAVIRT_SPINLOCK ?
2) experiments on further optimization possibilities.
(discussed in V6 of ticketlock)
3) possible debugfs cleanups (combining common code of Xen/KVM)

Let me know if you have any sugestion/comments...
---
V5 kernel changes:
https://lkml.org/lkml/2012/3/23/50
Qemu changes for V5:
http://lists.gnu.org/archive/html/qemu-devel/2012-03/msg04455.html

V4 kernel changes:
https://lkml.org/lkml/2012/1/14/66

Qemu changes for V4:
http://www.mail-archive.com/kvm [at] vger/msg66450.html

V3 kernel Changes:
https://lkml.org/lkml/2011/11/30/62
V2 kernel changes :
https://lkml.org/lkml/2011/10/23/207

Previous discussions : (posted by Srivatsa V).
https://lkml.org/lkml/2010/7/26/24
https://lkml.org/lkml/2011/1/19/212

Qemu patch for V3:
http://lists.gnu.org/archive/html/qemu-devel/2011-12/msg00397.html

Srivatsa Vaddagiri (3):
Add a hypercall to KVM hypervisor to support pv-ticketlocks
Added configuration support to enable debug information for KVM Guests
pv-ticketlock support for linux guests running on KVM hypervisor

Raghavendra K T (2):
Fold pv_unhalt flag into GET_MP_STATE ioctl to aid migration
Add documentation on Hypercalls and features used for PV spinlock

Documentation/virtual/kvm/api.txt | 7 +
Documentation/virtual/kvm/cpuid.txt | 4 +
Documentation/virtual/kvm/hypercalls.txt | 59 +++++++
arch/ia64/include/asm/kvm_host.h | 3 +
arch/powerpc/include/asm/kvm_host.h | 4 +
arch/s390/include/asm/kvm_host.h | 4 +
arch/x86/Kconfig | 9 +
arch/x86/include/asm/kvm_host.h | 6 +
arch/x86/include/asm/kvm_para.h | 16 ++-
arch/x86/kernel/kvm.c | 254 ++++++++++++++++++++++++++++++
arch/x86/kvm/cpuid.c | 3 +-
arch/x86/kvm/x86.c | 46 ++++++-
include/linux/kvm.h | 1 +
include/linux/kvm_para.h | 1 +
virt/kvm/kvm_main.c | 8 +
15 files changed, 421 insertions(+), 4 deletions(-)


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