| Message ID | 20250311094225.35129-2-sgarzare@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Enlightened vTPM support for SVSM on SEV-SNP | expand |
On Tue, Mar 11, 2025 at 10:42:22AM +0100, Stefano Garzarella wrote: > 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@HansenPartnership.com> > Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> > Co-developed-by: Claudio Carvalho <cclaudio@linux.ibm.com> > Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com> > Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> > --- > 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 | 31 +++++++++++++++++++++++++++++++ > 2 files changed, 38 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); > + > void __init snp_secure_tsc_prepare(void); > void __init snp_secure_tsc_init(void); > > diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c > index 96c7bc698e6b..2166bdff88b7 100644 > --- a/arch/x86/coco/sev/core.c > +++ b/arch/x86/coco/sev/core.c > @@ -2628,6 +2628,37 @@ static int snp_issue_guest_request(struct snp_guest_req *req, struct snp_req_dat > return ret; > } > Since this is an exported symbol, it'd be a good practice document snp_svsm_vtpm_probe(). > +bool snp_svsm_vtpm_probe(void) > +{ > + struct svsm_call call = {}; > + > + /* The vTPM device is available only if a SVSM is present */ > + if (!snp_vmpl) > + return false; > + > + call.caa = svsm_get_caa(); > + call.rax = SVSM_VTPM_CALL(SVSM_VTPM_QUERY); I supposed CAA is some kind of shared memory area for host and VM? > + > + if (svsm_perform_call_protocol(&call)) > + return false; > + > + /* Check platform commands contains TPM_SEND_COMMAND - platform command 8 */ > + return (call.rcx_out & BIT_ULL(8)) == BIT_ULL(8); > +} > +EXPORT_SYMBOL_GPL(snp_svsm_vtpm_probe); > + Ditto. > +int snp_svsm_vtpm_send_command(u8 *buffer) > +{ > + struct svsm_call call = {}; > + > + call.caa = svsm_get_caa(); > + call.rax = SVSM_VTPM_CALL(SVSM_VTPM_CMD); > + call.rcx = __pa(buffer); > + > + return svsm_perform_call_protocol(&call); > +} > +EXPORT_SYMBOL_GPL(snp_svsm_vtpm_send_command); > + > static struct platform_device sev_guest_device = { > .name = "sev-guest", > .id = -1, > -- > 2.48.1 > That said, these are rather self-documenting (i.e, nice and clean). BR, Jarkko
On Tue, Mar 11, 2025 at 11:56:23AM +0200, Jarkko Sakkinen wrote: >On Tue, Mar 11, 2025 at 10:42:22AM +0100, Stefano Garzarella wrote: >> 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@HansenPartnership.com> >> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> >> Co-developed-by: Claudio Carvalho <cclaudio@linux.ibm.com> >> Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com> >> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> >> --- >> 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 | 31 +++++++++++++++++++++++++++++++ >> 2 files changed, 38 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); >> + >> void __init snp_secure_tsc_prepare(void); >> void __init snp_secure_tsc_init(void); >> >> diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c >> index 96c7bc698e6b..2166bdff88b7 100644 >> --- a/arch/x86/coco/sev/core.c >> +++ b/arch/x86/coco/sev/core.c >> @@ -2628,6 +2628,37 @@ static int snp_issue_guest_request(struct snp_guest_req *req, struct snp_req_dat >> return ret; >> } >> > >Since this is an exported symbol, it'd be a good practice document >snp_svsm_vtpm_probe(). Yes, you are right, since the others were not documented, I had not added it, but I agree with you, I'll do in v4. > >> +bool snp_svsm_vtpm_probe(void) >> +{ >> + struct svsm_call call = {}; >> + >> + /* The vTPM device is available only if a SVSM is present */ >> + if (!snp_vmpl) >> + return false; >> + >> + call.caa = svsm_get_caa(); >> + call.rax = SVSM_VTPM_CALL(SVSM_VTPM_QUERY); > >I supposed CAA is some kind of shared memory area for host and VM? Not with the host, but with SVSM, which is the firmware running in the guest, but at a higher privilege level (VMPL) than the kernel, where, for example, the vTPM is emulated. BTW, yep it is a shared memory defined by the SVSM calling convention. From AMD SVSM specification: 5 Calling Convention Each call to the SVSM conveys data through a combination of the SVSM Calling Area (whose address was first configured through the SVSM_CAA field of the secrets page) and registers. Use of the Calling Area is necessary for the SVSM to detect the difference between a call that was issued by the guest and a spurious invocation by a poorly behaved host. Registers are used for all other parameters. The initially configured SVSM Calling Area is a page of memory that lies outside the initial SVSM memory range and has not had its VMPL permissions restricted in any way. The address is guaranteed to be aligned to a 4 KB boundary, so the remainder of the page may be used by the guest for memory-based parameter passing if desired. The contents of the Calling Area are described in the following table: Table 2: Calling Area Byte Size Name Description Offset 0x000 1 byte SVSM_CALL_PENDING Indicates whether a call has been requested by the guest (0=no call requested, 1=call requested). 0x001 1 byte SVSM_MEM_AVAILABLE Free memory is available to be withdrawn. 0x002 6 byte Reserved. The SVSM is not required to verify that these bytes are 0. > >> + >> + if (svsm_perform_call_protocol(&call)) >> + return false; >> + >> + /* Check platform commands contains TPM_SEND_COMMAND - platform command 8 */ >> + return (call.rcx_out & BIT_ULL(8)) == BIT_ULL(8); >> +} >> +EXPORT_SYMBOL_GPL(snp_svsm_vtpm_probe); >> + > >Ditto. Ack. > >> +int snp_svsm_vtpm_send_command(u8 *buffer) >> +{ >> + struct svsm_call call = {}; >> + >> + call.caa = svsm_get_caa(); >> + call.rax = SVSM_VTPM_CALL(SVSM_VTPM_CMD); >> + call.rcx = __pa(buffer); >> + >> + return svsm_perform_call_protocol(&call); >> +} >> +EXPORT_SYMBOL_GPL(snp_svsm_vtpm_send_command); >> + >> static struct platform_device sev_guest_device = { >> .name = "sev-guest", >> .id = -1, >> -- >> 2.48.1 >> > >That said, these are rather self-documenting (i.e, nice and clean). Thanks for the review! Stefano
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); + void __init snp_secure_tsc_prepare(void); void __init snp_secure_tsc_init(void); diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c index 96c7bc698e6b..2166bdff88b7 100644 --- a/arch/x86/coco/sev/core.c +++ b/arch/x86/coco/sev/core.c @@ -2628,6 +2628,37 @@ static int snp_issue_guest_request(struct snp_guest_req *req, struct snp_req_dat return ret; } +bool snp_svsm_vtpm_probe(void) +{ + struct svsm_call call = {}; + + /* The vTPM device is available only if a SVSM is present */ + if (!snp_vmpl) + return false; + + call.caa = svsm_get_caa(); + call.rax = SVSM_VTPM_CALL(SVSM_VTPM_QUERY); + + if (svsm_perform_call_protocol(&call)) + return false; + + /* Check platform commands contains TPM_SEND_COMMAND - platform command 8 */ + return (call.rcx_out & BIT_ULL(8)) == BIT_ULL(8); +} +EXPORT_SYMBOL_GPL(snp_svsm_vtpm_probe); + +int snp_svsm_vtpm_send_command(u8 *buffer) +{ + struct svsm_call call = {}; + + call.caa = svsm_get_caa(); + call.rax = SVSM_VTPM_CALL(SVSM_VTPM_CMD); + call.rcx = __pa(buffer); + + return svsm_perform_call_protocol(&call); +} +EXPORT_SYMBOL_GPL(snp_svsm_vtpm_send_command); + static struct platform_device sev_guest_device = { .name = "sev-guest", .id = -1,
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@HansenPartnership.com> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> Co-developed-by: Claudio Carvalho <cclaudio@linux.ibm.com> Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com> Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> --- 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 | 31 +++++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+)