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KVM: s390: Intercept the tprot instruction
Based on original patch from Jeng-fang (Nick) Wang When standby memory is specified for a guest Linux, but no virtual memory has been allocated on the Qemu host backing that guest, the guest memory detection process encounters a memory access exception which is not thrown from the KVM handle_tprot() instruction-handler function. The access exception comes from sie64a returning EFAULT, which then passes an addressing exception to the guest. Unfortunately this does not the proper PSW fixup (nullifying vs. suppressing) so the guest will get a fault for the wrong address. Let's just intercept the tprot instruction all the time to do the right thing and not go the page fault handler path for standby memory. tprot is only used by Linux during startup so some exits should be ok. Without this patch, standby memory cannot be used with KVM. Signed-off-by: Nick Wang <jfwang@us.ibm.com> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com> Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com> Tested-by: Matthew Rosato <mjrosato@linux.vnet.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
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2 changed files with 4 additions and 1 deletions
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@ -110,6 +110,7 @@ struct kvm_s390_sie_block {
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#define ICTL_ISKE 0x00004000
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#define ICTL_SSKE 0x00002000
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#define ICTL_RRBE 0x00001000
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#define ICTL_TPROT 0x00000200
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__u32 ictl; /* 0x0048 */
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__u32 eca; /* 0x004c */
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#define ICPT_INST 0x04
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@ -637,7 +637,9 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
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if (sclp_has_siif())
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vcpu->arch.sie_block->eca |= 1;
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vcpu->arch.sie_block->fac = (int) (long) vfacilities;
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vcpu->arch.sie_block->ictl |= ICTL_ISKE | ICTL_SSKE | ICTL_RRBE;
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vcpu->arch.sie_block->ictl |= ICTL_ISKE | ICTL_SSKE | ICTL_RRBE |
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ICTL_TPROT;
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if (kvm_s390_cmma_enabled(vcpu->kvm)) {
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rc = kvm_s390_vcpu_setup_cmma(vcpu);
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if (rc)
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