Re: [PATCH v4 1/4] x86/sev: add SVSM vTPM probe/send_command functions

[Stefano Garzarella]

On Tue, Mar 25, 2025 at 09:56:53AM -0700, Dionna Amalie Glaze wrote:
> On Mon, Mar 24, 2025 at 3:47 AM Stefano Garzarella <sgarzare@xxxxxxxxxx> wrote:
> > From: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> >
> > Add two new functions to probe and send commands to the SVSM vTPM.
> > They leverage the two calls defined by the AMD SVSM specification [1]
> > for the vTPM protocol: SVSM_VTPM_QUERY and SVSM_VTPM_CMD.
> >
> > Expose these functions to be used by other modules such as a tpm
> > driver.
> >
> > [1] "Secure VM Service Module for SEV-SNP Guests"
> >     Publication # 58019 Revision: 1.00
> >
> > Co-developed-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> > Co-developed-by: Claudio Carvalho <cclaudio@xxxxxxxxxxxxx>
> > Signed-off-by: Claudio Carvalho <cclaudio@xxxxxxxxxxxxx>
> > Reviewed-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
> > Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> > ---
> > v4:
> > - added Tom's R-b
> > - added functions documentation [Jarkko]
> > - simplified TPM_SEND_COMMAND check [Tom/Jarkko]
> > v3:
> > - removed link to the spec because those URLs are unstable [Borislav]
> > - squashed "x86/sev: add SVSM call macros for the vTPM protocol" patch
> >   in this one [Borislav]
> > - slimmed down snp_svsm_vtpm_probe() [Borislav]
> > - removed features check and any print related [Tom]
> > ---
> >  arch/x86/include/asm/sev.h |  7 +++++
> >  arch/x86/coco/sev/core.c   | 59 ++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 66 insertions(+)
> >
> > diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
> > index ba7999f66abe..09471d058ce5 100644
> > --- a/arch/x86/include/asm/sev.h
> > +++ b/arch/x86/include/asm/sev.h
> > @@ -384,6 +384,10 @@ struct svsm_call {
> >  #define SVSM_ATTEST_SERVICES           0
> >  #define SVSM_ATTEST_SINGLE_SERVICE     1
> >
> > +#define SVSM_VTPM_CALL(x)              ((2ULL << 32) | (x))
> > +#define SVSM_VTPM_QUERY                        0
> > +#define SVSM_VTPM_CMD                  1
> > +
> >  #ifdef CONFIG_AMD_MEM_ENCRYPT
> >
> >  extern u8 snp_vmpl;
> > @@ -481,6 +485,9 @@ void snp_msg_free(struct snp_msg_desc *mdesc);
> >  int snp_send_guest_request(struct snp_msg_desc *mdesc, struct snp_guest_req *req,
> >                            struct snp_guest_request_ioctl *rio);
> >
> > +bool snp_svsm_vtpm_probe(void);
> > +int snp_svsm_vtpm_send_command(u8 *buffer);
> > +
>
> These should be defined static inline with trivial definitions in the
> #else case, yes?

For now the only user of those is the tpm_svsm driver which is build 
only if CONFIG_AMD_MEM_ENCRYPT is defined, so there should be no 
problem, but you are right, better to follow the other functions and 
define the stubs

I'll fix in v5, good catch!

Thanks,
Stefano