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2014-05-06KVM: s390: return -EFAULT if copy_from_user() failsDan Carpenter1-2/+3
When copy_from_user() fails, this code returns the number of bytes remaining instead of a negative error code. The positive number is returned to the user but otherwise it is harmless. Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
2014-04-22KVM: s390: no timer interrupts when single-stepping a guestDavid Hildenbrand1-0/+2
When a guest is single-stepped, we want to disable timer interrupts. Otherwise, the guest will continuously execute the external interrupt handler and make debugging of code where timer interrupts are enabled almost impossible. The delivery of timer interrupts can be enforced in such sections by setting a breakpoint and continuing execution. In order to disable timer interrupts, they are disabled in the control register of the guest just before SIE entry and are suppressed in the interrupt check/delivery methods. Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com> Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
2014-04-22KVM: s390: hardware support for guest debuggingDavid Hildenbrand1-0/+479
This patch adds support to debug the guest using the PER facility on s390. Single-stepping, hardware breakpoints and hardware watchpoints are supported. In order to use the PER facility of the guest without it noticing it, the control registers of the guest have to be patched and access to them has to be intercepted(stctl, stctg, lctl, lctlg). All PER program interrupts have to be intercepted and only the relevant PER interrupts for the guest have to be given back. Special care has to be taken about repeated exits on the same hardware breakpoint. The intervention of the host in the guests PER configuration is not fully transparent. PER instruction nullification can not be used by the guest and too many storage alteration events may be reported to the guest (if it is activated for special address ranges only) when the host concurrently debugging it. Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>