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KVM: s390: Fix program check on interrupt delivery handling 

The current interrupt handling on s390 misbehaves on an error case. On s390
each cpu has the prefix area (lowcore) for interrupt delivery. This memory
must always be available. If we fail to access the prefix area for a guest
on interrupt delivery the configuration is completely unusable. There is no
point in sending another program interrupt to an inaccessible lowcore.
Furthermore, we should not bug the host kernel, because this can be triggered
by userspace. I think the guest kernel itself can not trigger the problem, as
SET PREFIX and SIGNAL PROCESSOR SET PREFIX both check that the memory is
available and sane. As this is a userspace bug (e.g. setting the wrong guest
offset, unmapping guest memory) we should kill the userspace process instead
of BUGing the host kernel.
In the long term we probably should notify the userspace process about this
problem.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>
This commit is contained in:
Christian Borntraeger 2008-07-25 15:51:54 +02:00 committed by Avi Kivity
parent 0096369daa
commit 3cd612998f
1 changed files with 7 additions and 14 deletions
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21
arch/s390/kvm/interrupt.c
View File

@ -13,6 +13,7 @@
#include <asm/lowcore.h> #include <asm/lowcore.h>
#include <asm/uaccess.h> #include <asm/uaccess.h>
#include <linux/kvm_host.h> #include <linux/kvm_host.h>
#include <linux/signal.h>
#include "kvm-s390.h" #include "kvm-s390.h"
#include "gaccess.h" #include "gaccess.h"
@ -246,15 +247,10 @@ static void __do_deliver_interrupt(struct kvm_vcpu *vcpu,
default: default:
BUG(); BUG();
} }
if (exception) { if (exception) {
VCPU_EVENT(vcpu, 1, "%s", "program exception while delivering" printk("kvm: The guest lowcore is not mapped during interrupt "
" interrupt"); "delivery, killing userspace\n");
kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING); do_exit(SIGKILL);
if (inti->type == KVM_S390_PROGRAM_INT) {
printk(KERN_WARNING "kvm: recursive program check\n");
BUG();
}
} }
} }
@ -277,14 +273,11 @@ static int __try_deliver_ckc_interrupt(struct kvm_vcpu *vcpu)
__LC_EXT_NEW_PSW, sizeof(psw_t)); __LC_EXT_NEW_PSW, sizeof(psw_t));
if (rc == -EFAULT) if (rc == -EFAULT)
exception = 1; exception = 1;
if (exception) { if (exception) {
VCPU_EVENT(vcpu, 1, "%s", "program exception while delivering" \ printk("kvm: The guest lowcore is not mapped during interrupt "
" ckc interrupt"); "delivery, killing userspace\n");
kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING); do_exit(SIGKILL);
return 0;
} }
return 1; return 1;
} }