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KVM: PPC: Book3S PR: Keep volatile reg values in vcpu rather than shadow_vcpu

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Currently PR-style KVM keeps the volatile guest register values
(R0 - R13, CR, LR, CTR, XER, PC) in a shadow_vcpu struct rather than
the main kvm_vcpu struct.  For 64-bit, the shadow_vcpu exists in two
places, a kmalloc'd struct and in the PACA, and it gets copied back
and forth in kvmppc_core_vcpu_load/put(), because the real-mode code
can't rely on being able to access the kmalloc'd struct.

This changes the code to copy the volatile values into the shadow_vcpu
as one of the last things done before entering the guest.  Similarly
the values are copied back out of the shadow_vcpu to the kvm_vcpu
immediately after exiting the guest.  We arrange for interrupts to be
still disabled at this point so that we can't get preempted on 64-bit
and end up copying values from the wrong PACA.

This means that the accessor functions in kvm_book3s.h for these
registers are greatly simplified, and are same between PR and HV KVM.
In places where accesses to shadow_vcpu fields are now replaced by
accesses to the kvm_vcpu, we can also remove the svcpu_get/put pairs.
Finally, on 64-bit, we don't need the kmalloc'd struct at all any more.

With this, the time to read the PVR one million times in a loop went
from 567.7ms to 575.5ms (averages of 6 values), an increase of about
1.4% for this worse-case test for guest entries and exits.  The
standard deviation of the measurements is about 11ms, so the
difference is only marginally significant statistically.

Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>
This commit is contained in:
Paul Mackerras
2013-09-20 14:52:43 +10:00
committed by Alexander Graf
parent f24817716e
commit a2d56020d1
9 changed files with 174 additions and 251 deletions
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7
arch/powerpc/kvm/trace.h
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@@ -101,17 +101,12 @@ TRACE_EVENT(kvm_exit,
),
TP_fast_assign(
#ifdef CONFIG_KVM_BOOK3S_PR
struct kvmppc_book3s_shadow_vcpu *svcpu;
#endif
__entry->exit_nr = exit_nr;
__entry->pc = kvmppc_get_pc(vcpu);
__entry->dar = kvmppc_get_fault_dar(vcpu);
__entry->msr = vcpu->arch.shared->msr;
#ifdef CONFIG_KVM_BOOK3S_PR
svcpu = svcpu_get(vcpu);
__entry->srr1 = svcpu->shadow_srr1;
svcpu_put(svcpu);
__entry->srr1 = vcpu->arch.shadow_srr1;
#endif
__entry->last_inst = vcpu->arch.last_inst;
),