Hi Sagi, On 10/28/25 2:20 PM, Sagi Shahar wrote: > TDX guests' registers cannot be initialized directly using
Previous patch used the term "TDX VMs". It will make the changelogs easier to read if the same terms are used consistently. > vcpu_regs_set(), hence the stack pointer needs to be initialized by > the guest itself, running boot code beginning at the reset vector. Sean highlighted in https://lore.kernel.org/lkml/[email protected]/ that the changelog requirements for selftests should follow Documentation/process/maintainer-kvm-x86.rst. This means that the changelogs should start with a short description of the change followed by the context and problem description (if needed). > > Expose the function to allocate the guest stack so that TDX > initialization code can allocate it itself and skip the allocation in > vm_arch_vcpu_add() in that case. TDX still allocates the stack in vm_arch_vcpu_add() though, no? Perhaps something like below (caveat is that KVM style is new to me also so consider this a draft): Introduce kvm_allocate_vcpu_stack() to allocate a vCPU's stack in preparation for TDX to allocate a vCPU's stack and initialize its stack pointer. TDX VMs' registers are protected state and cannot be initialized using the KVM_SET_REGS ioctl() that is used for normal VMs. A TDX vCPU's stack address will be a property of the TDX specific boot code that initializes the vCPUs' stack pointers at boot. > > Reviewed-by: Binbin Wu <[email protected]> > Signed-off-by: Sagi Shahar <[email protected]> > --- > .../selftests/kvm/include/x86/processor.h | 2 ++ > tools/testing/selftests/kvm/lib/x86/processor.c | 16 +++++++++++----- > 2 files changed, 13 insertions(+), 5 deletions(-) > > diff --git a/tools/testing/selftests/kvm/include/x86/processor.h > b/tools/testing/selftests/kvm/include/x86/processor.h > index 9caeb3de7df6..dba2b3d558d1 100644 > --- a/tools/testing/selftests/kvm/include/x86/processor.h > +++ b/tools/testing/selftests/kvm/include/x86/processor.h > @@ -1120,6 +1120,8 @@ static inline void vcpu_clear_cpuid_feature(struct > kvm_vcpu *vcpu, > vcpu_set_or_clear_cpuid_feature(vcpu, feature, false); > } > > +vm_vaddr_t kvm_allocate_vcpu_stack(struct kvm_vm *vm); > + > uint64_t vcpu_get_msr(struct kvm_vcpu *vcpu, uint64_t msr_index); > int _vcpu_set_msr(struct kvm_vcpu *vcpu, uint64_t msr_index, uint64_t > msr_value); > > diff --git a/tools/testing/selftests/kvm/lib/x86/processor.c > b/tools/testing/selftests/kvm/lib/x86/processor.c > index 2d1544e8af6c..2898fe4f6de4 100644 > --- a/tools/testing/selftests/kvm/lib/x86/processor.c > +++ b/tools/testing/selftests/kvm/lib/x86/processor.c > @@ -693,12 +693,9 @@ void vcpu_arch_set_entry_point(struct kvm_vcpu *vcpu, > void *guest_code) > vcpu_regs_set(vcpu, ®s); > } > > -struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id) > +vm_vaddr_t kvm_allocate_vcpu_stack(struct kvm_vm *vm) > { > - struct kvm_mp_state mp_state; > - struct kvm_regs regs; > vm_vaddr_t stack_vaddr; > - struct kvm_vcpu *vcpu; > > stack_vaddr = __vm_vaddr_alloc(vm, DEFAULT_STACK_PGS * getpagesize(), > DEFAULT_GUEST_STACK_VADDR_MIN, > @@ -719,6 +716,15 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, > uint32_t vcpu_id) > "__vm_vaddr_alloc() did not provide a page-aligned > address"); > stack_vaddr -= 8; > > + return stack_vaddr; > +} > + > +struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, uint32_t vcpu_id) > +{ > + struct kvm_mp_state mp_state; > + struct kvm_regs regs; > + struct kvm_vcpu *vcpu; Even though the original code did not do so I'd propose these declarations be in reverse fir order. > + > vcpu = __vm_vcpu_add(vm, vcpu_id); > vcpu_init_cpuid(vcpu, kvm_get_supported_cpuid()); > vcpu_init_sregs(vm, vcpu); > @@ -727,7 +733,7 @@ struct kvm_vcpu *vm_arch_vcpu_add(struct kvm_vm *vm, > uint32_t vcpu_id) > /* Setup guest general purpose registers */ > vcpu_regs_get(vcpu, ®s); > regs.rflags = regs.rflags | 0x2; > - regs.rsp = stack_vaddr; > + regs.rsp = kvm_allocate_vcpu_stack(vm); > vcpu_regs_set(vcpu, ®s); > > /* Setup the MP state */ Reinette
