On Tue, Jul 18, 2023 at 02:39:18PM -0500, Michael Roth <michael.roth@xxxxxxx> wrote: > On Mon, Jul 17, 2023 at 06:58:54PM -0700, isaku.yamahata@xxxxxxxxx wrote: > > From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > > > > TDX KVM will use KVM_MEM_ENC_OP. Make struct sev_cmd common both for > > vendor backend, SEV and TDX, with rename. Make the struct common uABI for > > KVM_MEM_ENC_OP. TDX backend wants to return 64 bit error code instead of > > 32 bit. To keep ABI for SEV backend, use union to accommodate 64 bit > > member. > > > > Some data structures for sub-commands could be common. The current > > candidate would be KVM_SEV{,_ES}_INIT, KVM_SEV_LAUNCH_FINISH, > > KVM_SEV_LAUNCH_UPDATE_VMSA, KVM_SEV_DBG_DECRYPT, and KVM_SEV_DBG_ENCRYPT. > > > > Only compile tested for SEV code. > > > > Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx> > > --- > > arch/x86/include/asm/kvm_host.h | 2 +- > > arch/x86/include/uapi/asm/kvm.h | 22 +++++++++++ > > arch/x86/kvm/svm/sev.c | 68 ++++++++++++++++++--------------- > > arch/x86/kvm/svm/svm.h | 2 +- > > arch/x86/kvm/x86.c | 16 +++++++- > > 5 files changed, 76 insertions(+), 34 deletions(-) > > > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > > index 28bd38303d70..f14c8df707ac 100644 > > --- a/arch/x86/include/asm/kvm_host.h > > +++ b/arch/x86/include/asm/kvm_host.h > > @@ -1706,7 +1706,7 @@ struct kvm_x86_ops { > > void (*enable_smi_window)(struct kvm_vcpu *vcpu); > > #endif > > > > - int (*mem_enc_ioctl)(struct kvm *kvm, void __user *argp); > > + int (*mem_enc_ioctl)(struct kvm *kvm, struct kvm_mem_enc_cmd *cmd); > > int (*mem_enc_register_region)(struct kvm *kvm, struct kvm_enc_region *argp); > > int (*mem_enc_unregister_region)(struct kvm *kvm, struct kvm_enc_region *argp); > > int (*vm_copy_enc_context_from)(struct kvm *kvm, unsigned int source_fd); > > diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h > > index 1a6a1f987949..c458c38bb0cb 100644 > > --- a/arch/x86/include/uapi/asm/kvm.h > > +++ b/arch/x86/include/uapi/asm/kvm.h > > @@ -562,4 +562,26 @@ struct kvm_pmu_event_filter { > > /* x86-specific KVM_EXIT_HYPERCALL flags. */ > > #define KVM_EXIT_HYPERCALL_LONG_MODE BIT(0) > > > > +struct kvm_mem_enc_cmd { > > + /* sub-command id of KVM_MEM_ENC_OP. */ > > + __u32 id; > > + /* Auxiliary flags for sub-command. */ > > + __u32 flags; > > struct kvm_sev_cmd doesn't have this flags field, so this would break for > older userspaces that try to pass it in instead of the struct kvm_mem_enc_cmd > proposed by this patch. Maybe move it to the end of the struct? Or > make it part of a TDX-specific union field. Please notice the padding. We don't have __packed attribute. struct kvm_sev_cmd { __u32 id; <<<<< 32bit padding here __u64 data; __u32 error; __u32 sev_fd; }; > But then you might also run into issues if you copy_to_user() with > sizeof(struct kvm_mem_enc_cmd) instead of sizeof(struct kvm_sev_cmd), > since the former might copy an additional 4 bytes more than what userspace > allocated. > > So maybe only common bits should be copy_to_user()'d by common KVM code, > and the platform-specific fields in the union should be separately copied > by platform code? > > E.g. > > struct kvm_mem_enc_sev_cmd { > __u32 error; > __u32 sev_fd; > } > > struct kvm_mem_enc_tdx_cmd { > __u64 error; > __u32 flags; > } > > struct kvm_mem_enc_cmd { > __u32 id; > __u64 data; > union { > struct kvm_mem_enc_sev_cmd sev_cmd; > struct kvm_mem_enc_tdx_cmd tdx_cmd; > } > }; > > But then we'd need to copy_from_user() for common header, then for > platform-specific sub-command metadata like sev_fd, then for the > sub-command-specific parameters themselves. > > Make me wonder if this warrants a KVM_MEM_ENC_OP2 (or whatever) that > uses the new structure from the start so that legacy constaints aren't > an issue. I'm fine with a new ioctl and deprecating the existing one. I'm looking for the least painful way to avoid unnecessary divergence. Not only for creation/attestation, but also for debug, migration, etc in near future. Thoughts? -- Isaku Yamahata <isaku.yamahata@xxxxxxxxx>