KVM: s390: fix memory overwrites when vx is disabled

The kernel now always uses vector registers when available, however KVM
has special logic if support is really enabled for a guest. If support
is disabled, guest_fpregs.fregs will only contain memory for the fpu.
The kernel, however, will store vector registers into that area,
resulting in crazy memory overwrites.

Simply extending that area is not enough, because the format of the
registers also changes. We would have to do additional conversions, making
the code even more complex. Therefore let's directly use one place for
the vector/fpu registers + fpc (in kvm_run). We just have to convert the
data properly when accessing it. This makes current code much easier.

Please note that vector/fpu registers are now always stored to
vcpu->run->s.regs.vrs. Although this data is visible to QEMU and
used for migration, we only guarantee valid values to user space  when
KVM_SYNC_VRS is set. As that is only the case when we have vector
register support, we are on the safe side.

Fixes: b5510d9b68c3 ("s390/fpu: always enable the vector facility if it is available")
Cc: stable@vger.kernel.org # v4.4 d9a3a09af54d s390/kvm: remove dependency on struct save_area definition
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
[adopt to d9a3a09af54d]

1 files changed, 0 insertions, 1 deletions

diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index 6742414dbd6f..8959ebb6d2c9 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -546,7 +546,6 @@ struct kvm_vcpu_arch {
 	struct kvm_s390_sie_block *sie_block;
 	unsigned int      host_acrs[NUM_ACRS];
 	struct fpu	  host_fpregs;
-	struct fpu	  guest_fpregs;
 	struct kvm_s390_local_interrupt local_int;
 	struct hrtimer    ckc_timer;
 	struct kvm_s390_pgm_info pgm;