From: Jarkko Sakkinen <jarkko@kernel.org>
Date: Mon, 4 Sep 2023 18:12:10 +0000 (+0300)
Subject: tpm: Enable hwrng only for Pluton on AMD CPUs
X-Git-Tag: archive/raspbian/6.1.52-1+rpi1^2~49
X-Git-Url: https://dgit.raspbian.org/%22http:/www.example.com/cgi/%22https:/%22bookmarks://%22Dat/%22http:/www.example.com/cgi/%22https:/%22bookmarks:/%22Dat?a=commitdiff_plain;h=aeebd48a46d602259245fc1abf0ea2856247e48b;p=linux.git

tpm: Enable hwrng only for Pluton on AMD CPUs

Origin: https://git.kernel.org/linus/8f7f35e5aa6f2182eabcfa3abef4d898a48e9aa8

The vendor check introduced by commit 554b841d4703 ("tpm: Disable RNG for
all AMD fTPMs") doesn't work properly on a number of Intel fTPMs.  On the
reported systems the TPM doesn't reply at bootup and returns back the
command code. This makes the TPM fail probe on Lenovo Legion Y540 laptop.

Since only Microsoft Pluton is the only known combination of AMD CPU and
fTPM from other vendor, disable hwrng otherwise. In order to make sysadmin
aware of this, print also info message to the klog.

Cc: stable@vger.kernel.org
Fixes: 554b841d4703 ("tpm: Disable RNG for all AMD fTPMs")
Reported-by: Todd Brandt <todd.e.brandt@intel.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217804
Reported-by: Patrick Steinhardt <ps@pks.im>
Reported-by: Raymond Jay Golo <rjgolo@gmail.com>
Reported-by: Ronan Pigott <ronan@rjp.ie>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

Gbp-Pq: Topic bugfix/x86
Gbp-Pq: Name tpm-Enable-hwrng-only-for-Pluton-on-AMD-CPUs.patch
---

diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index 7f7f3bded45..db0b774207d 100644
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -463,28 +463,6 @@ static bool crb_req_canceled(struct tpm_chip *chip, u8 status)
 	return (cancel & CRB_CANCEL_INVOKE) == CRB_CANCEL_INVOKE;
 }
 
-static int crb_check_flags(struct tpm_chip *chip)
-{
-	u32 val;
-	int ret;
-
-	ret = crb_request_locality(chip, 0);
-	if (ret)
-		return ret;
-
-	ret = tpm2_get_tpm_pt(chip, TPM2_PT_MANUFACTURER, &val, NULL);
-	if (ret)
-		goto release;
-
-	if (val == 0x414D4400U /* AMD */)
-		chip->flags |= TPM_CHIP_FLAG_HWRNG_DISABLED;
-
-release:
-	crb_relinquish_locality(chip, 0);
-
-	return ret;
-}
-
 static const struct tpm_class_ops tpm_crb = {
 	.flags = TPM_OPS_AUTO_STARTUP,
 	.status = crb_status,
@@ -826,9 +804,14 @@ static int crb_acpi_add(struct acpi_device *device)
 	if (rc)
 		goto out;
 
-	rc = crb_check_flags(chip);
-	if (rc)
-		goto out;
+#ifdef CONFIG_X86
+	/* A quirk for https://www.amd.com/en/support/kb/faq/pa-410 */
+	if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
+	    priv->sm != ACPI_TPM2_COMMAND_BUFFER_WITH_PLUTON) {
+		dev_info(dev, "Disabling hwrng\n");
+		chip->flags |= TPM_CHIP_FLAG_HWRNG_DISABLED;
+	}
+#endif /* CONFIG_X86 */
 
 	rc = tpm_chip_register(chip);