Messages in this thread | | | Date | Mon, 14 Aug 2023 10:30:30 +0200 | Subject | Re: [PATCH v2 5/5] virt: sevguest: Add TSM_REPORTS support for SNP_{GET, GET_EXT}_REPORT | From | Jeremi Piotrowski <> |
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On 8/14/2023 9:43 AM, 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. > > 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)
get_report and get_ext_report both have a:
lockdep_assert_held(&snp_cmd_mutex);
so you'd need to take that lock somewhere here.
Jeremi
> +{ > + struct snp_guest_dev *snp_dev = dev_get_drvdata(dev); > + const int report_size = SZ_16K; > + 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, > + }; > + > + 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, > + }; > + > + ret = get_report(snp_dev, &input, SNP_KARG); > + } > + > + if (ret) > + return ERR_PTR(ret); > + > + *outblob_len = size; > + no_free_ptr(buf); > + return buf; > +} > + > +static const struct tsm_ops sev_tsm_ops = { > + .name = KBUILD_MODNAME, > + .report_new = sev_report_new, > +}; > + > +static const struct attribute_group *sev_tsm_attribute_groups[] = { > + &tsm_default_attribute_group, > + &tsm_extra_attribute_group, > + NULL, > +}; > + > +static void unregister_sev_tsm(void *data) > +{ > + unregister_tsm(&sev_tsm_ops); > +} > + > static int __init sev_guest_probe(struct platform_device *pdev) > { > struct snp_secrets_page_layout *layout; > @@ -842,6 +915,14 @@ static int __init sev_guest_probe(struct platform_device *pdev) > snp_dev->input.resp_gpa = __pa(snp_dev->response); > snp_dev->input.data_gpa = __pa(snp_dev->certs_data); > > + ret = register_tsm(&sev_tsm_ops, &pdev->dev, sev_tsm_attribute_groups); > + if (ret) > + goto e_free_cert_data; > + > + ret = devm_add_action_or_reset(&pdev->dev, unregister_sev_tsm, NULL); > + if (ret) > + goto e_free_cert_data; > + > ret = misc_register(misc); > if (ret) > goto e_free_cert_data; >
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