Re: [RFC PATCH 17/21] coco/sev-guest: Implement the guest side of things

Jonathan Cameron
2024-08-28T15:54:45Z

On Fri, 23 Aug 2024 23:21:31 +1000
Alexey Kardashevskiy <aik@amd.com> wrote:

> Define tsm_ops for the guest and forward the ops calls to the HV via
> SVM_VMGEXIT_SEV_TIO_GUEST_REQUEST.
> Do the attestation report examination and enable MMIO.
>
> Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
More trivial stuff.

> diff --git a/drivers/virt/coco/sev-guest/sev_guest_tio.c b/drivers/virt/coco/sev-guest/sev_guest_tio.c
> new file mode 100644
> index 000000000000..33a082e7f039
> --- /dev/null
> +++ b/drivers/virt/coco/sev-guest/sev_guest_tio.c
> @@ -0,0 +1,513 @@

> +static int tio_tdi_sdte_write(struct tsm_tdi *tdi, struct snp_guest_dev *snp_dev, bool invalidate)
> +{
> + struct snp_guest_crypto *crypto = snp_dev->crypto;
> + size_t resp_len = sizeof(struct tio_msg_sdte_write_rsp) + crypto->a_len;
> + struct tio_msg_sdte_write_rsp *rsp = kzalloc(resp_len, GFP_KERNEL);
> + struct tio_msg_sdte_write_req req = {
> + .guest_device_id = pci_dev_id(tdi->pdev),
> + .sdte.vmpl = 0,
> + .sdte.vtom = tsm_vtom,
> + .sdte.vtom_en = 1,
> + .sdte.iw = 1,
> + .sdte.ir = 1,
> + .sdte.v = 1,
> + };
> + u64 fw_err = 0;
> + u64 bdfn = pci_dev_id(tdi->pdev);
> + int rc;
> +
> + BUILD_BUG_ON(sizeof(struct sdte) * 8 != 512);
> +
> + if (invalidate)
> + memset(&req, 0, sizeof(req));

Little odd to fill it then zero it. Maybe just fill it
if !invalidate

> +
> + pci_notice(tdi->pdev, "SDTE write vTOM=%lx", (unsigned long) req.sdte.vtom << 21);
> +
> + if (!rsp)

I'd allocate rsp down here as then obvious what is going on.

> + return -ENOMEM;
> +
> + rc = handle_tio_guest_request(snp_dev, TIO_MSG_SDTE_WRITE_REQ,
> + &req, sizeof(req), rsp, resp_len,
> + NULL, NULL, &bdfn, NULL, &fw_err);
> + if (rc) {
> + pci_err(tdi->pdev, "SDTE write failed with 0x%llx\n", fw_err);
> + goto free_exit;
> + }
> +
> +free_exit:
> + /* The response buffer contains the sensitive data, explicitly clear it. */
> + memzero_explicit(&rsp, sizeof(resp_len));
> + kfree(rsp);

kfree_sensitive() perhaps?

> + return rc;
> +}

> +static int sev_guest_tdi_validate(struct tsm_tdi *tdi, bool invalidate, void *private_data)
> +{
> + struct snp_guest_dev *snp_dev = private_data;
> + struct tsm_tdi_status ts = { 0 };
> + int ret;
> +
> + if (!tdi->report) {
> + ret = tio_tdi_status(tdi, snp_dev, &ts);
> +
> + if (ret || !tdi->report) {
> + pci_err(tdi->pdev, "No report available, ret=%d", ret);
> + if (!ret && tdi->report)
> + ret = -EIO;
> + return ret;
I'd split the error paths to simplify the logic.
if (ret) {
pci_err(tdi->pdev, "No report available, ret=%d", ret);
return ret;
}
if (!tdi->report) {
pci_err(... some more meaningful message)
return -EIO;
> + }
> +
> + if (ts.state != TDISP_STATE_RUN) {
> + pci_err(tdi->pdev, "Not in RUN state, state=%d instead", ts.state);
> + return -EIO;
> + }
> + }
> +
> + ret = tio_tdi_sdte_write(tdi, snp_dev, invalidate);
> + if (ret)
> + return ret;
> +
> + ret = tio_tdi_mmio_validate(tdi, snp_dev, invalidate);

return tio_tdi_mmio_validate();

> + if (ret)
> + return ret;
> +
> + return 0;
> +}