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Commit 60e21a0e authored by Will Deacon's avatar Will Deacon Committed by Marc Zyngier
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arm64: KVM: Take S1 walks into account when determining S2 write faults

The WnR bit in the HSR/ESR_EL2 indicates whether a data abort was
generated by a read or a write instruction. For stage 2 data aborts
generated by a stage 1 translation table walk (i.e. the actual page
table access faults at EL2), the WnR bit therefore reports whether the
instruction generating the walk was a load or a store, *not* whether the
page table walker was reading or writing the entry.

For page tables marked as read-only at stage 2 (e.g. due to KSM merging
them with the tables from another guest), this could result in livelock,
where a page table walk generated by a load instruction attempts to
set the access flag in the stage 1 descriptor, but fails to trigger
CoW in the host since only a read fault is reported.

This patch modifies the arm64 kvm_vcpu_dabt_iswrite function to
take into account stage 2 faults in stage 1 walks. Since DBM cannot be
disabled at EL2 for CPUs that implement it, we assume that these faults
are alw...
parent 1001354c
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......@@ -178,11 +178,6 @@ static inline bool kvm_vcpu_dabt_isvalid(const struct kvm_vcpu *vcpu)
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_ISV);
}
static inline bool kvm_vcpu_dabt_iswrite(const struct kvm_vcpu *vcpu)
{
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WNR);
}
static inline bool kvm_vcpu_dabt_issext(const struct kvm_vcpu *vcpu)
{
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_SSE);
......@@ -203,6 +198,12 @@ static inline bool kvm_vcpu_dabt_iss1tw(const struct kvm_vcpu *vcpu)
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_S1PTW);
}
static inline bool kvm_vcpu_dabt_iswrite(const struct kvm_vcpu *vcpu)
{
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WNR) ||
kvm_vcpu_dabt_iss1tw(vcpu); /* AF/DBM update */
}
static inline bool kvm_vcpu_dabt_is_cm(const struct kvm_vcpu *vcpu)
{
return !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_CM);
......
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