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authorPaolo Bonzini <pbonzini@redhat.com>2022-04-22 12:30:13 +0200
committerPaolo Bonzini <pbonzini@redhat.com>2022-04-29 12:38:22 -0400
commitd495f942f40aa412f8d4d65951152648cfa09903 (patch)
tree81a4c05ce5fb66d9bdcc613d35f235b5b93e951b /arch/arm64
parent86931ff7207bc045fa5439ef97b31859613dc303 (diff)
downloadlinux-d495f942f40aa412f8d4d65951152648cfa09903.tar.bz2
KVM: fix bad user ABI for KVM_EXIT_SYSTEM_EVENT
When KVM_EXIT_SYSTEM_EVENT was introduced, it included a flags member that at the time was unused. Unfortunately this extensibility mechanism has several issues: - x86 is not writing the member, so it would not be possible to use it on x86 except for new events - the member is not aligned to 64 bits, so the definition of the uAPI struct is incorrect for 32- on 64-bit userspace. This is a problem for RISC-V, which supports CONFIG_KVM_COMPAT, but fortunately usage of flags was only introduced in 5.18. Since padding has to be introduced, place a new field in there that tells if the flags field is valid. To allow further extensibility, in fact, change flags to an array of 16 values, and store how many of the values are valid. The availability of the new ndata field is tied to a system capability; all architectures are changed to fill in the field. To avoid breaking compilation of userspace that was using the flags field, provide a userspace-only union to overlap flags with data[0]. The new field is placed at the same offset for both 32- and 64-bit userspace. Cc: Will Deacon <will@kernel.org> Cc: Marc Zyngier <maz@kernel.org> Cc: Peter Gonda <pgonda@google.com> Cc: Sean Christopherson <seanjc@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reported-by: kernel test robot <lkp@intel.com> Message-Id: <20220422103013.34832-1-pbonzini@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/kvm/psci.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index baac2b405f23..708d80e8e60d 100644
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -181,7 +181,8 @@ static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type, u64 flags)
memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
vcpu->run->system_event.type = type;
- vcpu->run->system_event.flags = flags;
+ vcpu->run->system_event.ndata = 1;
+ vcpu->run->system_event.data[0] = flags;
vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
}