On Wed, Jul 22, 2026 at 11:13:13PM +0000, Lisa Wang wrote: > From: Erdem Aktas <[email protected]> > > Add code to boot a TDX test VM. Since TDX registers are inaccessible to > KVM, the boot code loads the relevant values from memory into the > registers before jumping to the guest code. > > Reviewed-by: Binbin Wu <[email protected]> > Signed-off-by: Erdem Aktas <[email protected]> > Co-developed-by: Ackerley Tng <[email protected]> > Signed-off-by: Ackerley Tng <[email protected]> > Co-developed-by: Sagi Shahar <[email protected]> > Signed-off-by: Sagi Shahar <[email protected]> > Signed-off-by: Lisa Wang <[email protected]> > ---
[ ... ] > diff --git a/tools/testing/selftests/kvm/include/x86/tdx/td_boot.h > b/tools/testing/selftests/kvm/include/x86/tdx/td_boot.h > index bf2282931d49..89cf6c3485be 100644 > --- a/tools/testing/selftests/kvm/include/x86/tdx/td_boot.h > +++ b/tools/testing/selftests/kvm/include/x86/tdx/td_boot.h > @@ -2,9 +2,6 @@ > #ifndef SELFTEST_TDX_TD_BOOT_H > #define SELFTEST_TDX_TD_BOOT_H > > -#include <linux/compiler.h> > -#include <linux/types.h> > - > /* > * Layout for boot section (not to scale) > * > @@ -24,7 +21,19 @@ > * | | > * | | > * |___________________________|____ 0x0_ffff_0000: TD_BOOT_PARAMETERS_GPA > + * > + * TD_BOOT_PARAMETERS_GPA is arbitrarily chosen to > + * > + * + be within the 4GB address space > + * + provide enough contiguous memory for the struct td_boot_parameters such > + * that there is one struct td_per_vcpu_parameters for KVM_MAX_VCPUS > */ > +#define TD_BOOT_PARAMETERS_GPA 0xffff0000 > + > +#if !defined(__ASSEMBLY__) && !defined(__ASSEMBLER__) Is the "__ASSEMBLY__" check really needed here? I don't think the toolchain uses -D__ASSEMBLY__... Also, I think __ASSEMBLY__ is slowly being removed from the tree [1][2]. [1] https://lore.kernel.org/all/[email protected]/ [2] https://lore.kernel.org/all/[email protected]/ > + > +#include <linux/compiler.h> > +#include <linux/types.h> > > /* > * The exact memory layout for LGDT or LIDT instructions. > @@ -63,4 +72,11 @@ struct td_boot_parameters { > struct td_per_vcpu_parameters per_vcpu[]; > }; > > +void td_boot(void); > +void td_boot_code_end(void); This looks a bit off to me. td_boot_code_end is just a symbol and not a function at all. Maybe something like this? extern u8 td_boot_code_start[], td_boot_code_end[]; > + > +#define TD_BOOT_CODE_SIZE (td_boot_code_end - td_boot) > + > +#endif /* !defined(__ASSEMBLY__) && !defined(__ASSEMBLER__) */ > + > #endif /* SELFTEST_TDX_TD_BOOT_H */ > diff --git a/tools/testing/selftests/kvm/lib/x86/tdx/td_boot.S > b/tools/testing/selftests/kvm/lib/x86/tdx/td_boot.S > new file mode 100644 > index 000000000000..bca9a4c3d8f8 > --- /dev/null > +++ b/tools/testing/selftests/kvm/lib/x86/tdx/td_boot.S > @@ -0,0 +1,61 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > + > +#include "tdx/td_boot.h" > +#include "tdx/td_boot_offsets.h" > +#include "processor_asm.h" > + > +.code32 > + > +.globl td_boot > +td_boot: > + /* > + * In this procedure, edi is used as a temporary register. Hmm, "mul %esi" clobbers edx as well. Not sure if that needs to be called out. Perhaps documenting the registers that need to be preserved thoughout this procedure (eax, ebx) is more useful. A comment below already mentions that edi is a scratch register. > + * Paging is turned off. > + */ > + cli > + > + movl $TD_BOOT_PARAMETERS_GPA, %ebx > + > + /* > + * Find the address of struct td_per_vcpu_parameters for this > + * vCPU based on esi (TDX spec: initialized with vCPU id). Put > + * struct address into register for indirect addressing. ^^^^^^^^ maybe just say eax? > + */ > + movl $SIZEOF_TD_PER_VCPU_PARAMETERS, %eax > + mul %esi > + leal TD_BOOT_PARAMETERS_PER_VCPU(%ebx), %edi > + addl %edi, %eax > +
