Messages in this thread | | | Subject | Re: [PATCH 2/4] KVM: s390: vsie: Fix length of facility list shadowed | From | Nina Schoetterl-Glausch <> | Date | Mon, 06 Nov 2023 14:06:22 +0100 |
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On Fri, 2023-11-03 at 19:34 +0100, David Hildenbrand wrote: > On 03.11.23 18:30, Nina Schoetterl-Glausch wrote: > > The length of the facility list accessed when interpretively executing > > STFLE is the same as the hosts facility list (in case of format-0) > > When shadowing, copy only those bytes. > > The memory following the facility list need not be accessible, in which > > case we'd wrongly inject a validity intercept. > > > > Fixes: 66b630d5b7f2 ("KVM: s390: vsie: support STFLE interpretation") > > Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com> > > --- > > arch/s390/include/asm/facility.h | 6 ++++++ > > arch/s390/kernel/Makefile | 2 +- > > arch/s390/kernel/facility.c | 18 ++++++++++++++++++ > > arch/s390/kvm/vsie.c | 12 +++++++++++- > > 4 files changed, 36 insertions(+), 2 deletions(-) > > create mode 100644 arch/s390/kernel/facility.c
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> > diff --git a/arch/s390/kernel/facility.c b/arch/s390/kernel/facility.c
[...]
> > +#include <asm/facility.h> > > + > > +unsigned int stfle_size(void) > > +{ > > + static unsigned int size = 0; > > + u64 dummy; > > + > > + if (!size) { > > + size = __stfle_asm(&dummy, 1) + 1; > > + } > > + return size; > > +} > > +EXPORT_SYMBOL(stfle_size); > > Possible races? Should have to use an atomic?
Good point. Calling __stfle_asm multiple times is fine and AFAIK torn reads/writes aren't possible. I don't see a way for the compiler to break things either. But it might indeed be nicer to use an atomic, without any downsides.
> > No access to documentation, but sounds plausible. > > Acked-by: David Hildenbrand <david@redhat.com>
Thanks!
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