From d495f942f40aa412f8d4d65951152648cfa09903 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 22 Apr 2022 12:30:13 +0200 Subject: 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 Cc: Marc Zyngier Cc: Peter Gonda Cc: Sean Christopherson Signed-off-by: Paolo Bonzini Reported-by: kernel test robot Message-Id: <20220422103013.34832-1-pbonzini@redhat.com> Signed-off-by: Paolo Bonzini --- include/uapi/linux/kvm.h | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 91a6fe4e02c0..6a184d260c7f 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -445,7 +445,13 @@ struct kvm_run { #define KVM_SYSTEM_EVENT_RESET 2 #define KVM_SYSTEM_EVENT_CRASH 3 __u32 type; - __u64 flags; + __u32 ndata; + union { +#ifndef __KERNEL__ + __u64 flags; +#endif + __u64 data[16]; + }; } system_event; /* KVM_EXIT_S390_STSI */ struct { @@ -1144,6 +1150,8 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_S390_MEM_OP_EXTENSION 211 #define KVM_CAP_PMU_CAPABILITY 212 #define KVM_CAP_DISABLE_QUIRKS2 213 +/* #define KVM_CAP_VM_TSC_CONTROL 214 */ +#define KVM_CAP_SYSTEM_EVENT_DATA 215 #ifdef KVM_CAP_IRQ_ROUTING -- cgit v1.2.3