On 22.08.2018 12:31, Janosch Frank wrote: > On 22.08.2018 11:53, David Hildenbrand wrote: >> When DATA exceptions and vector-processing exceptions (program interrupts) >> are injected, the DXC/VXC is also to be stored in the fpc, if AFP is >> enabled in CR0. >> >> This can happen inside KVM when reinjecting an interrupt during program >> interrupt intercepts. These are triggered for example when debugging the >> guest (concurrent PER events result in an intercept instead of an >> injection of such interrupts). >> >> Signed-off-by: David Hildenbrand <[email protected]> >> --- >> >> Only compile-tested. > > It baffles me that AFP is still a thing in zArch mode. I would have > expected it to be a default 1. But then again, I just found out about it. > > POP checks out: > Reviewed-by: Janosch Frank <[email protected]> > > >> >> arch/s390/include/asm/ctl_reg.h | 1 + >> arch/s390/kvm/interrupt.c | 8 ++++++++ >> 2 files changed, 9 insertions(+) >> >> diff --git a/arch/s390/include/asm/ctl_reg.h >> b/arch/s390/include/asm/ctl_reg.h >> index 4600453536c2..88f3f14baee9 100644 >> --- a/arch/s390/include/asm/ctl_reg.h >> +++ b/arch/s390/include/asm/ctl_reg.h >> @@ -11,6 +11,7 @@ >> #include <linux/const.h> >> >> #define CR0_CLOCK_COMPARATOR_SIGN _BITUL(63 - 10) >> +#define CR0_AFP_REGISTER_CONTROL _BITUL(63 - 45) >> #define CR0_EMERGENCY_SIGNAL_SUBMASK _BITUL(63 - 49) >> #define CR0_EXTERNAL_CALL_SUBMASK _BITUL(63 - 50) >> #define CR0_CLOCK_COMPARATOR_SUBMASK _BITUL(63 - 52) >> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c >> index fcb55b02990e..5b5754d8f460 100644 >> --- a/arch/s390/kvm/interrupt.c >> +++ b/arch/s390/kvm/interrupt.c >> @@ -765,6 +765,14 @@ static int __must_check __deliver_prog(struct kvm_vcpu >> *vcpu) >> break; >> case PGM_VECTOR_PROCESSING: >> case PGM_DATA: >> + if (vcpu->arch.sie_block->gcr[0] & CR0_AFP_REGISTER_CONTROL) { >> + /* make sure the new fpc will be lazily loaded */ >> + save_fpu_regs(); >> + /* the DXC/VXC cannot make the fpc invalid */ >> + current->thread.fpu.fpc &= ~0xff00u; >> + current->thread.fpu.fpc |= (pgm_info.data_exc_code << 8) >> + & 0xff00u; > > Everything except that byte should be 0 anyway when it comes from > lowcore, why do you mask?
User space can inject such an interrupt and could therefore set reserved bits, leading to a crash (fpc invalid when loaded). E.g. via kvm_s390_set_irq_state(). As of now, DXC/VXC is always 1byte. The other ones are to be stored as 0. (what we expect to always hold for now but user space can do crazy things) Thanks! > >> + } >> rc = put_guest_lc(vcpu, pgm_info.data_exc_code, >> (u32 *)__LC_DATA_EXC_CODE); >> break; >> > > -- Thanks, David / dhildenb
