From: Nina Schoetterl-Glausch <nsg@xxxxxxxxxxxxx> The length of the facility list accessed when interpretively executing STFLE is the same as the hosts facility list (in case of format-0) The memory following the facility list doesn't need to be accessible. The current VSIE implementation accesses a fixed length that exceeds the guest/host facility list length and can therefore wrongly inject a validity intercept. Instead, find out the host facility list length by running STFLE and copy only as much as necessary when shadowing. Acked-by: David Hildenbrand <david@xxxxxxxxxx> Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> Acked-by: Heiko Carstens <hca@xxxxxxxxxxxxx> Signed-off-by: Nina Schoetterl-Glausch <nsg@xxxxxxxxxxxxx> Reviewed-by: Janosch Frank <frankja@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20231219140854.1042599-3-nsg@xxxxxxxxxxxxx Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx> Message-ID: <20231219140854.1042599-3-nsg@xxxxxxxxxxxxx> --- arch/s390/include/asm/facility.h | 6 ++++++ arch/s390/kernel/Makefile | 2 +- arch/s390/kernel/facility.c | 21 +++++++++++++++++++++ arch/s390/kvm/vsie.c | 12 +++++++++++- 4 files changed, 39 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 353def93973b..7a562b4199c8 100644 --- a/arch/s390/kernel/Makefile +++ b/arch/s390/kernel/Makefile @@ -41,7 +41,7 @@ obj-y += sysinfo.o lgr.o os_info.o ctlreg.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..f02127219a27 --- /dev/null +++ b/arch/s390/kernel/facility.c @@ -0,0 +1,21 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright IBM Corp. 2023 + */ + +#include <asm/facility.h> + +unsigned int stfle_size(void) +{ + static unsigned int size; + unsigned int r; + u64 dummy; + + r = READ_ONCE(size); + if (!r) { + r = __stfle_asm(&dummy, 1) + 1; + WRITE_ONCE(size, r); + } + return r; +} +EXPORT_SYMBOL(stfle_size); diff --git a/arch/s390/kvm/vsie.c b/arch/s390/kvm/vsie.c index 3cf95bc0401d..aa8f4ab11e33 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" @@ -990,6 +991,10 @@ 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)) { retry_vsie_icpt(vsie_page); /* @@ -997,8 +1002,13 @@ static int handle_stfle(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page) * so we need to mask here before reading. */ fac = fac & 0x7ffffff8U; + /* + * 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; } -- 2.43.0
