On Fri, Dec 09, 2022 at 09:03:45PM +0000, Sean Christopherson wrote: [...]
> > - GUEST_ASSERT(0); > > +out: > > + /* > > + * If the guest cannot grab a ucall structure from the pool then the > > + * only option to get out to userspace is a bare ucall. This is probably > > + * a good time to mention that guest assertions depend on ucalls with > > + * arguments too. > > + */ > > + GUEST_UCALL_NONE(); > > UCALL_NONE isn't much better than infinite stack recursion, e.g. a test might > end > up passing by dumb luck, or go in the wrong direction because it sometimes > handles > UCALL_NONE. Oh, I was just seeking an end to my misery. Yeah, we can use a magic value to signal this instead. > How about this? LGTM. -- Thanks, Oliver > From: Sean Christopherson <[email protected]> > Date: Fri, 9 Dec 2022 12:55:44 -0800 > Subject: [PATCH] KVM: selftests: Use magic value to signal ucall_alloc() > failure > > Use a magic value to signal a ucall_alloc() failure instead of simply > doing GUEST_ASSERT(). GUEST_ASSERT() relies on ucall_alloc() and so a > failure puts the guest into an infinite loop. > > Use -1 as the magic value, as a real ucall struct should never wrap. > > Reported-by: Oliver Upton <[email protected]> > Signed-off-by: Sean Christopherson <[email protected]> > --- > tools/testing/selftests/kvm/lib/ucall_common.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/kvm/lib/ucall_common.c > b/tools/testing/selftests/kvm/lib/ucall_common.c > index 0cc0971ce60e..2f0e2ea941cc 100644 > --- a/tools/testing/selftests/kvm/lib/ucall_common.c > +++ b/tools/testing/selftests/kvm/lib/ucall_common.c > @@ -4,6 +4,8 @@ > #include "linux/bitmap.h" > #include "linux/atomic.h" > > +#define GUEST_UCALL_FAILED -1 > + > struct ucall_header { > DECLARE_BITMAP(in_use, KVM_MAX_VCPUS); > struct ucall ucalls[KVM_MAX_VCPUS]; > @@ -41,7 +43,8 @@ static struct ucall *ucall_alloc(void) > struct ucall *uc; > int i; > > - GUEST_ASSERT(ucall_pool); > + if (!ucall_pool) > + goto ucall_failed; > > for (i = 0; i < KVM_MAX_VCPUS; ++i) { > if (!test_and_set_bit(i, ucall_pool->in_use)) { > @@ -51,7 +54,13 @@ static struct ucall *ucall_alloc(void) > } > } > > - GUEST_ASSERT(0); > +ucall_failed: > + /* > + * If the vCPU cannot grab a ucall structure, make a bare ucall with a > + * magic value to signal to get_ucall() that things went sideways. > + * GUEST_ASSERT() depends on ucall_alloc() and so cannot be used here. > + */ > + ucall_arch_do_ucall(GUEST_UCALL_FAILED); > return NULL; > } > > @@ -93,6 +102,9 @@ uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc) > > addr = ucall_arch_get_ucall(vcpu); > if (addr) { > + TEST_ASSERT(addr != (void *)GUEST_UCALL_FAILED, > + "Guest failed to allocate ucall struct"); > + > memcpy(uc, addr, sizeof(*uc)); > vcpu_run_complete_io(vcpu); > } else { > > base-commit: dc2efbe4813e0dc4368779bc36c5f0e636cb8eb2 > -- > _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
