On 10.03.20 14:23, Christian Borntraeger wrote:

On 10.03.20 14:21, David Hildenbrand wrote:

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On 10.03.20 14:12, Christian Borntraeger wrote:

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When we do the initial CPU reset we must not only clear the registers in the internal data structures but also in kvm_run sync_regs. For modern userspace sync_regs is the only place that it looks at.

Cc: stable@vger.kernel.org

# v?

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Signed-off-by: Christian Borntraeger borntraeger@de.ibm.com

arch/s390/kvm/kvm-s390.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c index d7ff30e45589..c2e6d4ba4e23 100644 --- a/arch/s390/kvm/kvm-s390.c +++ b/arch/s390/kvm/kvm-s390.c @@ -3268,7 +3268,10 @@ static void kvm_arch_vcpu_ioctl_initial_reset(struct kvm_vcpu *vcpu) /* Initial reset is a superset of the normal reset */ kvm_arch_vcpu_ioctl_normal_reset(vcpu);

• /* this equals initial cpu reset in pop, but we don't switch to ESA */

• /*

• * This equals initial cpu reset in pop, but we don't switch to ESA.
  

• * We do not only reset the internal data, but also ...
  

• */
  

  vcpu->arch.sie_block->gpsw.mask = 0; vcpu->arch.sie_block->gpsw.addr = 0; kvm_s390_set_prefix(vcpu, 0);

@@ -3278,6 +3281,19 @@ static void kvm_arch_vcpu_ioctl_initial_reset(struct kvm_vcpu *vcpu) memset(vcpu->arch.sie_block->gcr, 0, sizeof(vcpu->arch.sie_block->gcr)); vcpu->arch.sie_block->gcr[0] = CR0_INITIAL_MASK; vcpu->arch.sie_block->gcr[14] = CR14_INITIAL_MASK;

• /* ... the data in sync regs */
• memset(vcpu->run->s.regs.crs, 0, sizeof(vcpu->run->s.regs.crs));
• vcpu->run->s.regs.ckc = 0;
• vcpu->run->s.regs.crs[0] = CR0_INITIAL_MASK;
• vcpu->run->s.regs.crs[14] = CR14_INITIAL_MASK;
• vcpu->run->psw_addr = 0;
• vcpu->run->psw_mask = 0;
• vcpu->run->s.regs.todpr = 0;
• vcpu->run->s.regs.cputm = 0;
• vcpu->run->s.regs.ckc = 0;
• vcpu->run->s.regs.pp = 0;
• vcpu->run->s.regs.gbea = 1; vcpu->run->s.regs.fpc = 0; vcpu->arch.sie_block->gbea = 1; vcpu->arch.sie_block->pp = 0;

Acked-by: David Hildenbrand david@redhat.com

However, I do wonder if that ioctl *originally* was designed for that - IOW if this is rally a stable patch or just some change that makes sense. IIRC, userspace/QEMU always did the right thing, no? There was no documentation about the guarantees AFAIK.

Yes, I moved forth and back. Maybe removing cc stable and just adding Fixes: 7de3f1423ff ("KVM: s390: Add new reset vcpu API") is better then.

Makes sense.