On 09.02.20 16:50, Thomas Huth wrote:
> On 07/02/2020 12.39, Christian Borntraeger wrote:
>> From: Janosch Frank <frankja@xxxxxxxxxxxxx>
>>
>> A lot of the registers are controlled by the Ultravisor and never
>> visible to KVM. Also some registers are overlayed, like gbea is with
>> sidad, which might leak data to userspace.
>>
>> Hence we sync a minimal set of registers for both SIE formats and then
>> check and sync format 2 registers if necessary.
>>
>> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
>> [borntraeger@xxxxxxxxxx: patch merging, splitting, fixing]
>> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
>> ---
>> arch/s390/kvm/kvm-s390.c | 116 ++++++++++++++++++++++++---------------
>> 1 file changed, 72 insertions(+), 44 deletions(-)
>>
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index f995040102ea..7df48cc942fd 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -3447,9 +3447,11 @@ static void kvm_arch_vcpu_ioctl_initial_reset(struct kvm_vcpu *vcpu)
>> vcpu->arch.sie_block->gcr[0] = CR0_INITIAL_MASK;
>> vcpu->arch.sie_block->gcr[14] = CR14_INITIAL_MASK;
>> vcpu->run->s.regs.fpc = 0;
>> - vcpu->arch.sie_block->gbea = 1;
>> - vcpu->arch.sie_block->pp = 0;
>> - vcpu->arch.sie_block->fpf &= ~FPF_BPBC;
>> + if (!kvm_s390_pv_handle_cpu(vcpu)) {
>> + vcpu->arch.sie_block->gbea = 1;
>> + vcpu->arch.sie_block->pp = 0;
>> + vcpu->arch.sie_block->fpf &= ~FPF_BPBC;
>> + }
>
> Technically, this part is not about sync'ing but about reset ... worth
> to mention this in the patch description, too? (or maybe even move to
> the reset patch 34/35 or a new patch?)
Will move into a separate patch.
>
> And what about vcpu->arch.sie_block->todpr ? Should that be moved into
> the if-statement, too?
Yes, todpr is not accessible by the KVM and should go in here
>
>> }
>>
>> static void kvm_arch_vcpu_ioctl_clear_reset(struct kvm_vcpu *vcpu)
>> @@ -4060,25 +4062,16 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
>> return rc;
>> }
>>
>> -static void sync_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>> +static void sync_regs_fmt2(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>> {
>> struct runtime_instr_cb *riccb;
>> struct gs_cb *gscb;
>>
>> - riccb = (struct runtime_instr_cb *) &kvm_run->s.regs.riccb;
>> - gscb = (struct gs_cb *) &kvm_run->s.regs.gscb;
>> vcpu->arch.sie_block->gpsw.mask = kvm_run->psw_mask;
>> vcpu->arch.sie_block->gpsw.addr = kvm_run->psw_addr;
>> - if (kvm_run->kvm_dirty_regs & KVM_SYNC_PREFIX)
>> - kvm_s390_set_prefix(vcpu, kvm_run->s.regs.prefix);
>> - if (kvm_run->kvm_dirty_regs & KVM_SYNC_CRS) {
>> - memcpy(&vcpu->arch.sie_block->gcr, &kvm_run->s.regs.crs, 128);
>> - /* some control register changes require a tlb flush */
>> - kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
>> - }
>> + riccb = (struct runtime_instr_cb *) &kvm_run->s.regs.riccb;
>> + gscb = (struct gs_cb *) &kvm_run->s.regs.gscb;
>
> You could leave the riccb and gscb lines at the beginning to make the
> diff a little bit nicer.
ack.
>
>> if (kvm_run->kvm_dirty_regs & KVM_SYNC_ARCH0) {
>> - kvm_s390_set_cpu_timer(vcpu, kvm_run->s.regs.cputm);
>> - vcpu->arch.sie_block->ckc = kvm_run->s.regs.ckc;
>> vcpu->arch.sie_block->todpr = kvm_run->s.regs.todpr;
>> vcpu->arch.sie_block->pp = kvm_run->s.regs.pp;
>> vcpu->arch.sie_block->gbea = kvm_run->s.regs.gbea;
>> @@ -4119,6 +4112,47 @@ static void sync_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>> vcpu->arch.sie_block->fpf &= ~FPF_BPBC;
>> vcpu->arch.sie_block->fpf |= kvm_run->s.regs.bpbc ? FPF_BPBC : 0;
>> }
>> + if (MACHINE_HAS_GS) {
>> + preempt_disable();
>> + __ctl_set_bit(2, 4);
>> + if (current->thread.gs_cb) {
>> + vcpu->arch.host_gscb = current->thread.gs_cb;
>> + save_gs_cb(vcpu->arch.host_gscb);
>> + }
>> + if (vcpu->arch.gs_enabled) {
>> + current->thread.gs_cb = (struct gs_cb *)
>> + &vcpu->run->s.regs.gscb;
>> + restore_gs_cb(current->thread.gs_cb);
>> + }
>> + preempt_enable();
>> + }
>> + /* SIE will load etoken directly from SDNX and therefore kvm_run */
>> +}
>> +
>> +static void sync_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>> +{
>> + /*
>> + * at several places we have to modify our internal view to not do
>> + * things that are disallowed by the ultravisor. For example we must
>> + * not inject interrupts after specific exits (e.g. 112). We do this
>> + * by turning off the MIE bits of our PSW copy. To avoid getting
>> + * validity intercepts, we do only accept the condition code from
>> + * userspace.
>> + */
>> + vcpu->arch.sie_block->gpsw.mask &= ~PSW_MASK_CC;
>> + vcpu->arch.sie_block->gpsw.mask |= kvm_run->psw_mask & PSW_MASK_CC;
>
> I think it would be cleaner to only do this for protected guests. You
> could combine it with the call to sync_regs_fmt2():
>
> if (likely(!kvm_s390_pv_is_protected(vcpu->kvm))) {
> sync_regs_fmt2(vcpu, kvm_run);
> } else {
> vcpu->arch.sie_block->gpsw.mask &= ~PSW_MASK_CC;
> vcpu->arch.sie_block->gpsw.mask |= kvm_run->psw_mask &
> PSW_MASK_CC;
> }
I like that.
[...]
>> static void store_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>> @@ -4161,12 +4203,9 @@ static void store_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>> kvm_run->s.regs.cputm = kvm_s390_get_cpu_timer(vcpu);
>> kvm_run->s.regs.ckc = vcpu->arch.sie_block->ckc;
>> kvm_run->s.regs.todpr = vcpu->arch.sie_block->todpr;
>
> TODPR handling has been move from sync_regs() to sync_regs_fmt2() ...
> should this here move from store_regs() to store_regs_fmt2(), too?
ack.
>
> And maybe you should also not read the sie_block->gpsw.addr (and some of
> the control registers) field in store_regs() either, i.e. move the lines
> to store_regs_fmt2()?
>
>> - kvm_run->s.regs.pp = vcpu->arch.sie_block->pp;
>> - kvm_run->s.regs.gbea = vcpu->arch.sie_block->gbea;
>> kvm_run->s.regs.pft = vcpu->arch.pfault_token;
>> kvm_run->s.regs.pfs = vcpu->arch.pfault_select;
>> kvm_run->s.regs.pfc = vcpu->arch.pfault_compare;
>> - kvm_run->s.regs.bpbc = (vcpu->arch.sie_block->fpf & FPF_BPBC) == FPF_BPBC;
>> save_access_regs(vcpu->run->s.regs.acrs);
>> restore_access_regs(vcpu->arch.host_acrs);
>> /* Save guest register state */
>> @@ -4175,19 +4214,8 @@ static void store_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>> /* Restore will be done lazily at return */
>> current->thread.fpu.fpc = vcpu->arch.host_fpregs.fpc;
>> current->thread.fpu.regs = vcpu->arch.host_fpregs.regs;
>> - if (MACHINE_HAS_GS) {
>> - __ctl_set_bit(2, 4);
>> - if (vcpu->arch.gs_enabled)
>> - save_gs_cb(current->thread.gs_cb);
>> - preempt_disable();
>> - current->thread.gs_cb = vcpu->arch.host_gscb;
>> - restore_gs_cb(vcpu->arch.host_gscb);
>> - preempt_enable();
>> - if (!vcpu->arch.host_gscb)
>> - __ctl_clear_bit(2, 4);
>> - vcpu->arch.host_gscb = NULL;
>> - }
>> - /* SIE will save etoken directly into SDNX and therefore kvm_run */
>> + if (likely(!kvm_s390_pv_is_protected(vcpu->kvm)))
>> + store_regs_fmt2(vcpu, kvm_run);
>> }
>>
>> int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>>
>
> Thomas
>
