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i386/kvm: correct the meaning of '0xffffffff' value for hv-spinlocks

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Hyper-V TLFS prior to version 6.0 had a mistake in it: special value
'0xffffffff' for CPUID 0x40000004.EBX was called 'never to retry', this
looked weird (like why it's not '0' which supposedly have the same effect?)
but nobody raised the question. In TLFS version 6.0 the mistake was
corrected to 'never notify' which sounds logical. Fix QEMU accordingly.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Message-Id: <20200515114847.74523-1-vkuznets@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
This commit is contained in:
Vitaly Kuznetsov 2020-05-15 13:48:47 +02:00 committed by Eduardo Habkost
parent 053a417781
commit f701c082e7
4 changed files with 6 additions and 6 deletions
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2
docs/hyperv.txt
View File

@ -49,7 +49,7 @@ more efficiently. In particular, this enlightenment allows paravirtualized
======================
Enables paravirtualized spinlocks. The parameter indicates how many times
spinlock acquisition should be attempted before indicating the situation to the
hypervisor. A special value 0xffffffff indicates "never to retry".
hypervisor. A special value 0xffffffff indicates "never notify".
3.4. hv-vpindex
================

2
target/i386/cpu.c
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@ -7263,7 +7263,7 @@ static Property x86_cpu_properties[] = {
DEFINE_PROP_BOOL("pmu", X86CPU, enable_pmu, false),
DEFINE_PROP_UINT32("hv-spinlocks", X86CPU, hyperv_spinlock_attempts,
HYPERV_SPINLOCK_NEVER_RETRY),
HYPERV_SPINLOCK_NEVER_NOTIFY),
DEFINE_PROP_BIT64("hv-relaxed", X86CPU, hyperv_features,
HYPERV_FEAT_RELAXED, 0),
DEFINE_PROP_BIT64("hv-vapic", X86CPU, hyperv_features,

4
target/i386/cpu.h
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@ -991,8 +991,8 @@ typedef uint64_t FeatureWordArray[FEATURE_WORDS];
#define HYPERV_FEAT_IPI 13
#define HYPERV_FEAT_STIMER_DIRECT 14
#ifndef HYPERV_SPINLOCK_NEVER_RETRY
#define HYPERV_SPINLOCK_NEVER_RETRY 0xFFFFFFFF
#ifndef HYPERV_SPINLOCK_NEVER_NOTIFY
#define HYPERV_SPINLOCK_NEVER_NOTIFY 0xFFFFFFFF
#endif
#define EXCP00_DIVZ 0

4
target/i386/kvm.c
View File

@ -730,7 +730,7 @@ static bool hyperv_enabled(X86CPU *cpu)
{
CPUState *cs = CPU(cpu);
return kvm_check_extension(cs->kvm_state, KVM_CAP_HYPERV) > 0 &&
((cpu->hyperv_spinlock_attempts != HYPERV_SPINLOCK_NEVER_RETRY) ||
((cpu->hyperv_spinlock_attempts != HYPERV_SPINLOCK_NEVER_NOTIFY) ||
cpu->hyperv_features || cpu->hyperv_passthrough);
}
@ -1236,7 +1236,7 @@ static int hyperv_handle_properties(CPUState *cs,
env->features[FEAT_HV_RECOMM_EAX] = c->eax;
/* hv-spinlocks may have been overriden */
if (cpu->hyperv_spinlock_attempts != HYPERV_SPINLOCK_NEVER_RETRY) {
if (cpu->hyperv_spinlock_attempts != HYPERV_SPINLOCK_NEVER_NOTIFY) {
c->ebx = cpu->hyperv_spinlock_attempts;
}
}