Messages in this thread | | | Date | Tue, 15 Aug 2023 14:40:38 -0700 | From | Dan Williams <> | Subject | Re: [PATCH v2 5/5] virt: sevguest: Add TSM_REPORTS support for SNP_{GET, GET_EXT}_REPORT |
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Tom Lendacky wrote: > On 8/14/23 02:43, Dan Williams wrote: > > The sevguest driver was a first mover in the confidential computing > > space. As a first mover that afforded some leeway to build the driver > > without concern for common infrastructure. > > > > Now that sevguest is no longer a singleton [1] the common operation of > > building and transmitting attestation report blobs can / should be made > > common. In this model the so called "TSM-provider" implementations can > > share a common envelope ABI even if the contents of that envelope remain > > vendor-specific. When / if the industry agrees on an attestation record > > format, that definition can also fit in the same ABI. In the meantime > > the kernel's maintenance burden is reduced and collaboration on the > > commons is increased. > > > > Convert sevguest to use CONFIG_TSM_REPORTS to retrieve the blobs that > > the SNP_{GET,GET_EXT}_REPORT ioctls produce. An example flow for > > retrieving the SNP_GET_REPORT blob via the TSM interface utility, > > assuming no nonce and VMPL==2: > > > > echo 2 > /sys/class/tsm/tsm0/privlevel > > dd if=/dev/urandom bs=64 count=1 | xxd -p -c 0 > /sys/class/tsm/tsm0/inhex > > hexdump -C /sys/class/tsm/tsm0/outblob > > > > ...while the SNP_GET_EXT_REPORT flow needs to additionally set the > > format to "extended": > > > > echo 2 > /sys/class/tsm/tsm0/privlevel > > echo extended > /sys/class/tsm/tsm0/format > > dd if=/dev/urandom bs=64 count=1 | xxd -p -c 0 > /sys/class/tsm/tsm0/inhex > > hexdump -C /sys/class/tsm/tsm0/outblob > > > > The old ioctls can be lazily deprecated, the main motivation of this > > effort is to stop the proliferation of new ioctls, and to increase > > cross-vendor colloboration. > > > > Note, only compile-tested. > > I just got back from vacation, so I'll apply and test as soon as I get a
Appreciate it! Hold off on testing until v3 though since Peter highlighted I am misusing no_free_ptr(), Jeremi pointed out that sev-guest locking is being violated, and configfs may need to be deployed for this to future proof the ABI for future use cases.
> chance. > > > > > Link: http://lore.kernel.org/r/64961c3baf8ce_142af829436@dwillia2-xfh.jf.intel.com.notmuch [1] > > Cc: Borislav Petkov <bp@alien8.de> > > Cc: Tom Lendacky <thomas.lendacky@amd.com> > > Cc: Dionna Glaze <dionnaglaze@google.com> > > Cc: Brijesh Singh <brijesh.singh@amd.com> > > Signed-off-by: Dan Williams <dan.j.williams@intel.com> > > --- > > drivers/virt/coco/sev-guest/Kconfig | 1 > > drivers/virt/coco/sev-guest/sev-guest.c | 81 +++++++++++++++++++++++++++++++ > > 2 files changed, 82 insertions(+) > > > > diff --git a/drivers/virt/coco/sev-guest/Kconfig b/drivers/virt/coco/sev-guest/Kconfig > > index da2d7ca531f0..1cffc72c41cb 100644 > > --- a/drivers/virt/coco/sev-guest/Kconfig > > +++ b/drivers/virt/coco/sev-guest/Kconfig > > @@ -5,6 +5,7 @@ config SEV_GUEST > > select CRYPTO > > select CRYPTO_AEAD2 > > select CRYPTO_GCM > > + select TSM_REPORTS > > help > > SEV-SNP firmware provides the guest a mechanism to communicate with > > the PSP without risk from a malicious hypervisor who wishes to read, > > diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c > > index f48c4764a7a2..5941081502e8 100644 > > --- a/drivers/virt/coco/sev-guest/sev-guest.c > > +++ b/drivers/virt/coco/sev-guest/sev-guest.c > > @@ -16,6 +16,7 @@ > > #include <linux/miscdevice.h> > > #include <linux/set_memory.h> > > #include <linux/fs.h> > > +#include <linux/tsm.h> > > #include <crypto/aead.h> > > #include <linux/scatterlist.h> > > #include <linux/psp-sev.h> > > @@ -769,6 +770,78 @@ static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno > > return key; > > } > > > > +static u8 *sev_report_new(struct device *dev, const struct tsm_desc *desc, > > + size_t *outblob_len) > > +{ > > + struct snp_guest_dev *snp_dev = dev_get_drvdata(dev); > > + const int report_size = SZ_16K; > > The response buffer from the PSP is limited to 4K, so the report size can > be SZ_4K.
Oh, ok, what about the extended case?
> > > + const int ext_size = SZ_16K; > > + int ret, size; > > + > > + if (desc->inblob_len != 64) > > + return ERR_PTR(-EINVAL); > > + > > + if (desc->outblob_format == TSM_FORMAT_EXTENDED) > > + size = report_size + ext_size; > > + else > > + size = report_size; > > + > > + u8 *buf __free(kvfree) = kvzalloc(size, GFP_KERNEL); > > + > > + if (desc->outblob_format == TSM_FORMAT_EXTENDED) { > > + struct snp_ext_report_req ext_req = { > > + .data = { .vmpl = desc->privlevel }, > > + .certs_address = (__u64)buf + report_size, > > + .certs_len = ext_size, > > + }; > > + memcpy(&ext_req.data.user_data, desc->inblob, desc->inblob_len); > > + > > + struct snp_guest_request_ioctl input = { > > + .msg_version = 1, > > + .req_data = (__u64)&ext_req, > > + .resp_data = (__u64)buf, > > + }; > > Won't the compiler complain about this declaration being after the memcpy()?
The memcpy is into @ext_req, @input is just referencing @ext_req.
> > > + > > + ret = get_ext_report(snp_dev, &input, SNP_KARG); > > + } else { > > + struct snp_report_req req = { > > + .vmpl = desc->privlevel, > > + }; > > + memcpy(&req.user_data, desc->inblob, desc->inblob_len); > > + > > + struct snp_guest_request_ioctl input = { > > + .msg_version = 1, > > + .req_data = (__u64) &req, > > + .resp_data = (__u64) buf, > > + }; > > Ditto here. >
I think its ok, but let me know if you think I am missing something. Thanks for taking a look!
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