Messages in this thread | | | Date | Fri, 28 Jul 2023 09:28:58 +0200 | Subject | Re: [PATCH] KVM: s390: fix sthyi error handling | From | Christian Borntraeger <> |
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Am 27.07.23 um 20:29 schrieb Heiko Carstens: > Commit 9fb6c9b3fea1 ("s390/sthyi: add cache to store hypervisor info") > added cache handling for store hypervisor info. This also changed the > possible return code for sthyi_fill(). > > Instead of only returning a condition code like the sthyi instruction would > do, it can now also return a negative error value (-ENOMEM). handle_styhi() > was not changed accordingly. In case of an error, the negative error value > would incorrectly injected into the guest PSW. > > Add proper error handling to prevent this, and update the comment which > describes the possible return values of sthyi_fill().
To me it looks like this can only happen if page allocation fails? This should not happen in normal cases (and return -ENOMEM would likely kill the guest as QEMU would stop). But if it happens we better stop.
Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
> > Fixes: 9fb6c9b3fea1 ("s390/sthyi: add cache to store hypervisor info") > Signed-off-by: Heiko Carstens <hca@linux.ibm.com> > --- > arch/s390/kernel/sthyi.c | 6 +++--- > arch/s390/kvm/intercept.c | 9 ++++++--- > 2 files changed, 9 insertions(+), 6 deletions(-) > > diff --git a/arch/s390/kernel/sthyi.c b/arch/s390/kernel/sthyi.c > index 4d141e2c132e..2ea7f208f0e7 100644 > --- a/arch/s390/kernel/sthyi.c > +++ b/arch/s390/kernel/sthyi.c > @@ -459,9 +459,9 @@ static int sthyi_update_cache(u64 *rc) > * > * Fills the destination with system information returned by the STHYI > * instruction. The data is generated by emulation or execution of STHYI, > - * if available. The return value is the condition code that would be > - * returned, the rc parameter is the return code which is passed in > - * register R2 + 1. > + * if available. The return value is either a negative error value or > + * the condition code that would be returned, the rc parameter is the > + * return code which is passed in register R2 + 1. > */ > int sthyi_fill(void *dst, u64 *rc) > { > diff --git a/arch/s390/kvm/intercept.c b/arch/s390/kvm/intercept.c > index 954d39adf85c..341abafb96e4 100644 > --- a/arch/s390/kvm/intercept.c > +++ b/arch/s390/kvm/intercept.c > @@ -389,8 +389,8 @@ static int handle_partial_execution(struct kvm_vcpu *vcpu) > */ > int handle_sthyi(struct kvm_vcpu *vcpu) > { > - int reg1, reg2, r = 0; > - u64 code, addr, cc = 0, rc = 0; > + int reg1, reg2, cc = 0, r = 0; > + u64 code, addr, rc = 0; > struct sthyi_sctns *sctns = NULL; > > if (!test_kvm_facility(vcpu->kvm, 74)) > @@ -421,7 +421,10 @@ int handle_sthyi(struct kvm_vcpu *vcpu) > return -ENOMEM; > > cc = sthyi_fill(sctns, &rc); > - > + if (cc < 0) { > + free_page((unsigned long)sctns); > + return cc; > + } > out: > if (!cc) { > if (kvm_s390_pv_cpu_is_protected(vcpu)) {
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