| Message ID | 20231103173008.630217-3-nsg@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: s390: Fix minor bugs in STFLE shadowing | expand |
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 > > diff --git a/arch/s390/include/asm/facility.h b/arch/s390/include/asm/facility.h > index 94b6919026df..796007125dff 100644 > --- a/arch/s390/include/asm/facility.h > +++ b/arch/s390/include/asm/facility.h > @@ -111,4 +111,10 @@ static inline void stfle(u64 *stfle_fac_list, int size) > preempt_enable(); > } > > +/** > + * stfle_size - Actual size of the facility list as specified by stfle > + * (number of double words) > + */ > +unsigned int stfle_size(void); > + > #endif /* __ASM_FACILITY_H */ > diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile > index 0df2b88cc0da..0daa81439478 100644 > --- a/arch/s390/kernel/Makefile > +++ b/arch/s390/kernel/Makefile > @@ -41,7 +41,7 @@ obj-y += sysinfo.o lgr.o os_info.o > obj-y += runtime_instr.o cache.o fpu.o dumpstack.o guarded_storage.o sthyi.o > obj-y += entry.o reipl.o kdebugfs.o alternative.o > obj-y += nospec-branch.o ipl_vmparm.o machine_kexec_reloc.o unwind_bc.o > -obj-y += smp.o text_amode31.o stacktrace.o abs_lowcore.o > +obj-y += smp.o text_amode31.o stacktrace.o abs_lowcore.o facility.o > > extra-y += vmlinux.lds > > diff --git a/arch/s390/kernel/facility.c b/arch/s390/kernel/facility.c > new file mode 100644 > index 000000000000..c33a95a562da > --- /dev/null > +++ b/arch/s390/kernel/facility.c > @@ -0,0 +1,18 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright IBM Corp. 2023 > + */ > + > +#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? No access to documentation, but sounds plausible. Acked-by: David Hildenbrand <david@redhat.com>
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 [...] > > 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!
On Mon, Nov 06, 2023 at 02:06:22PM +0100, Nina Schoetterl-Glausch wrote: > > > +unsigned int stfle_size(void) > > > +{ > > > + static unsigned int size = 0; > > > + u64 dummy; > > > + > > > + if (!size) { > > > + size = __stfle_asm(&dummy, 1) + 1; > > > + } Please get rid of the braces here. checkpatch.pl with "--strict" should complain too, I guess. > > 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. Please use WRITE_ONCE() and READ_ONCE(); that's more than sufficient here.
diff --git a/arch/s390/include/asm/facility.h b/arch/s390/include/asm/facility.h index 94b6919026df..796007125dff 100644 --- a/arch/s390/include/asm/facility.h +++ b/arch/s390/include/asm/facility.h @@ -111,4 +111,10 @@ static inline void stfle(u64 *stfle_fac_list, int size) preempt_enable(); } +/** + * stfle_size - Actual size of the facility list as specified by stfle + * (number of double words) + */ +unsigned int stfle_size(void); + #endif /* __ASM_FACILITY_H */ diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile index 0df2b88cc0da..0daa81439478 100644 --- a/arch/s390/kernel/Makefile +++ b/arch/s390/kernel/Makefile @@ -41,7 +41,7 @@ obj-y += sysinfo.o lgr.o os_info.o obj-y += runtime_instr.o cache.o fpu.o dumpstack.o guarded_storage.o sthyi.o obj-y += entry.o reipl.o kdebugfs.o alternative.o obj-y += nospec-branch.o ipl_vmparm.o machine_kexec_reloc.o unwind_bc.o -obj-y += smp.o text_amode31.o stacktrace.o abs_lowcore.o +obj-y += smp.o text_amode31.o stacktrace.o abs_lowcore.o facility.o extra-y += vmlinux.lds diff --git a/arch/s390/kernel/facility.c b/arch/s390/kernel/facility.c new file mode 100644 index 000000000000..c33a95a562da --- /dev/null +++ b/arch/s390/kernel/facility.c @@ -0,0 +1,18 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright IBM Corp. 2023 + */ + +#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); diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c index d989772fe211..c168e88c64da 100644 --- a/arch/s390/kvm/vsie.c +++ b/arch/s390/kvm/vsie.c @@ -19,6 +19,7 @@ #include <asm/nmi.h> #include <asm/dis.h> #include <asm/fpu/api.h> +#include <asm/facility.h> #include "kvm-s390.h" #include "gaccess.h" @@ -990,11 +991,20 @@ static int handle_stfle(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page) struct kvm_s390_sie_block *scb_s = &vsie_page->scb_s; __u32 fac = READ_ONCE(vsie_page->scb_o->fac); + /* + * Alternate-STFLE-Interpretive-Execution facilities are not supported + * -> format-0 flcb + */ if (fac && test_kvm_facility(vcpu->kvm, 7)) { fac = fac & 0x7ffffff8U; retry_vsie_icpt(vsie_page); + /* + * format-0 -> size of nested guest's facility list == guest's size + * guest's size == host's size, since STFLE is interpretatively executed + * using a format-0 for the guest, too. + */ if (read_guest_real(vcpu, fac, &vsie_page->fac, - sizeof(vsie_page->fac))) + stfle_size() * sizeof(u64))) return set_validity_icpt(scb_s, 0x1090U); scb_s->fac = (__u32)(__u64) &vsie_page->fac; }
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