linux-kernel - Re: [PATCH v4 1/4] x86/sev: add SVSM vTPM probe/send

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Message-ID: <4euvodfh537v3hiiotkmugdknhpy3oxpy7kq5zcxilbpbdop6q@qgwwm557czjv>
Date: Thu, 27 Mar 2025 10:59:12 +0100
From: Stefano Garzarella <sgarzare@...hat.com>
To: Jarkko Sakkinen <jarkko@...nel.org>
Cc: Dionna Amalie Glaze <dionnaglaze@...gle.com>, 
	Joerg Roedel <jroedel@...e.de>, Ingo Molnar <mingo@...hat.com>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, Peter Huewe <peterhuewe@....de>, 
	Tom Lendacky <thomas.lendacky@....com>, Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org, 
	James Bottomley <James.Bottomley@...senpartnership.com>, linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>, 
	Jason Gunthorpe <jgg@...pe.ca>, "H. Peter Anvin" <hpa@...or.com>, linux-coco@...ts.linux.dev, 
	Claudio Carvalho <cclaudio@...ux.ibm.com>, Dov Murik <dovmurik@...ux.ibm.com>, 
	linux-integrity@...r.kernel.org
Subject: Re: [PATCH v4 1/4] x86/sev: add SVSM vTPM probe/send_command
 functions

On Wed, Mar 26, 2025 at 07:14:22PM +0200, Jarkko Sakkinen wrote:
>On Tue, Mar 25, 2025 at 06:20:48PM +0100, Stefano Garzarella wrote:
>> 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@...hat.com> wrote:
>> > >
>> > > From: Stefano Garzarella <sgarzare@...hat.com>
>> > >
>> > > 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@...senPartnership.com>
>> > > Signed-off-by: James Bottomley <James.Bottomley@...senPartnership.com>
>> > > Co-developed-by: Claudio Carvalho <cclaudio@...ux.ibm.com>
>> > > Signed-off-by: Claudio Carvalho <cclaudio@...ux.ibm.com>
>> > > Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
>> > > Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
>> > > ---
>> > > 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!
>
>Only denoting here that you can keep my reviewed-by in the v5 for
>this despite the minor change.

Thanks for pointing that out!
Stefano