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From:   Steffen Eiden <seiden@linux.ibm.com>
To:     kvm@vger.kernel.org, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Viktor Mihajlovski <mihajlov@linux.ibm.com>
Cc:     Janosch Frank <frankja@linux.ibm.com>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>,
        Nico Boehr <nrb@linux.ibm.com>,
        Christian Borntraeger <borntraeger@linux.ibm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Hendrik Brueckner <brueckner@linux.ibm.com>
Subject: [PATCH 1/5] s390/uvdevice: Add info IOCTL
Date:   Fri, 12 May 2023 11:31:49 +0200
Message-Id: <20230512093153.206378-2-seiden@linux.ibm.com>
In-Reply-To: <20230512093153.206378-1-seiden@linux.ibm.com>
References: <20230512093153.206378-1-seiden@linux.ibm.com>
MIME-Version: 1.0
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Add an IOCTL that allows userspace to find out which IOCTLs the uvdevice
supports without trial and error.

Explicitly expose the IOCTL nr for the request types.

Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
---
 arch/s390/include/uapi/asm/uvdevice.h | 45 +++++++++++++++-
 drivers/s390/char/uvdevice.c          | 77 ++++++++++++++++++++++++---
 2 files changed, 114 insertions(+), 8 deletions(-)

diff --git a/arch/s390/include/uapi/asm/uvdevice.h b/arch/s390/include/uapi/asm/uvdevice.h
index 10a5ac918e02..ed58979b8438 100644
--- a/arch/s390/include/uapi/asm/uvdevice.h
+++ b/arch/s390/include/uapi/asm/uvdevice.h
@@ -32,6 +32,36 @@ struct uvio_attest {
 	__u16 reserved136;				/* 0x0136 */
 };
 
+/**
+ * uvio_uvdev_info - Information of supported functions
+ *
+ * @supp_uvio_cmds - supported IOCTLs by this device
+ * @supp_uv_cmds - supported UVCs corresponding to the IOCTL
+ *
+ * UVIO request to get information about supported request types by this
+ * uvdevice and the Ultravisor.
+ * Everything is output. Bits are in LSB0 ordering.
+ * If the bit is set in both, @supp_uvio_cmds and @supp_uv_cmds,
+ * the uvdevice and the Ultravisor support that call.
+ *
+ * Note that bit 0 (UVIO_IOCTL_UVDEV_INFO_NR) is always zero for `supp_uv_cmds`
+ * as there is no corresponding UV-call.
+ */
+struct uvio_uvdev_info {
+	/*
+	 * If bit `n` is set, this device supports the IOCTL with nr `n`.
+	 */
+	__u64 supp_uvio_cmds;
+	/*
+	 * If bit `n` is set, the Ultravisor(UV) supports the UV-call
+	 * corresponding to the IOCTL with nr `n` in the calling contextx
+	 * (host or guest).
+	 * The value is only valid if the corresponding bit in @supp_uvio_cmds
+	 * is set as well.
+	 */
+	__u64 supp_uv_cmds;
+};
+
 /*
  * The following max values define an upper length for the IOCTL in/out buffers.
  * However, they do not represent the maximum the Ultravisor allows which is
@@ -46,6 +76,19 @@ struct uvio_attest {
 #define UVIO_DEVICE_NAME "uv"
 #define UVIO_TYPE_UVC 'u'
 
-#define UVIO_IOCTL_ATT _IOWR(UVIO_TYPE_UVC, 0x01, struct uvio_ioctl_cb)
+enum UVIO_IOCTL_NR {
+	UVIO_IOCTL_UVDEV_INFO_NR = 0x00,
+	UVIO_IOCTL_ATT_NR,
+	/* must be the last entry */
+	UVIO_IOCTL_NUM_IOCTLS
+};
+
+#define UVIO_IOCTL(nr)		_IOWR(UVIO_TYPE_UVC, nr, struct uvio_ioctl_cb)
+#define UVIO_IOCTL_UVDEV_INFO	UVIO_IOCTL(UVIO_IOCTL_UVDEV_INFO_NR)
+#define UVIO_IOCTL_ATT		UVIO_IOCTL(UVIO_IOCTL_ATT_NR)
+
+#define UVIO_SUPP_CALL(nr)	(1ULL << (nr))
+#define UVIO_SUPP_UDEV_INFO	UVIO_SUPP_CALL(UVIO_IOCTL_UDEV_INFO_NR)
+#define UVIO_SUPP_ATT		UVIO_SUPP_CALL(UVIO_IOCTL_ATT_NR)
 
 #endif /* __S390_ASM_UVDEVICE_H */
diff --git a/drivers/s390/char/uvdevice.c b/drivers/s390/char/uvdevice.c
index 1d40457c7b10..27f5bf1cf27a 100644
--- a/drivers/s390/char/uvdevice.c
+++ b/drivers/s390/char/uvdevice.c
@@ -20,6 +20,7 @@
  *  channel for userspace to the Ultravisor.
  */
 
+#include "asm-generic/ioctl.h"
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/miscdevice.h>
@@ -32,6 +33,51 @@
 #include <asm/uvdevice.h>
 #include <asm/uv.h>
 
+/* Mapping from IOCTL-nr to UVC-bit */
+static const u64 ioctl_nr_to_uvc_bit[] __initconst = {
+	[UVIO_IOCTL_UVDEV_INFO_NR] = -1UL,
+	[UVIO_IOCTL_ATT_NR] = BIT_UVC_CMD_RETR_ATTEST,
+};
+
+static_assert(ARRAY_SIZE(ioctl_nr_to_uvc_bit) == UVIO_IOCTL_NUM_IOCTLS);
+
+static struct uvio_uvdev_info uvdev_info = {
+	.supp_uvio_cmds = GENMASK_ULL(UVIO_IOCTL_NUM_IOCTLS - 1, 0),
+};
+
+static void __init set_supp_uv_cmds(struct uvio_uvdev_info *info)
+{
+	int i;
+
+	for (i = 0; i < UVIO_IOCTL_NUM_IOCTLS; i++) {
+		if (ioctl_nr_to_uvc_bit[i] == -1UL)
+			continue;
+		if (!test_bit_inv(ioctl_nr_to_uvc_bit[i], uv_info.inst_calls_list))
+			continue;
+		set_bit(i, (unsigned long *)&info->supp_uv_cmds);
+	}
+}
+
+/**
+ * uvio_uvdev_info() - get information about the uvdevice
+ *
+ * @uv_ioctl: ioctl control block
+ *
+ * Lists all supported IOCTLs by this uvdevice
+ */
+static int uvio_uvdev_info(struct uvio_ioctl_cb *uv_ioctl)
+{
+	void __user *user_buf_arg = (void __user *)uv_ioctl->argument_addr;
+
+	if (uv_ioctl->argument_len < sizeof(uvdev_info))
+		return -EINVAL;
+	if (copy_to_user(user_buf_arg, &uvdev_info, sizeof(uvdev_info)))
+		return -EFAULT;
+
+	uv_ioctl->uv_rc = UVC_RC_EXECUTED;
+	return  0;
+}
+
 static int uvio_build_uvcb_attest(struct uv_cb_attest *uvcb_attest, u8 *arcb,
 				  u8 *meas, u8 *add_data, struct uvio_attest *uvio_attest)
 {
@@ -185,8 +231,19 @@ static int uvio_attestation(struct uvio_ioctl_cb *uv_ioctl)
 	return ret;
 }
 
-static int uvio_copy_and_check_ioctl(struct uvio_ioctl_cb *ioctl, void __user *argp)
+static int uvio_copy_and_check_ioctl(struct uvio_ioctl_cb *ioctl, void __user *argp,
+				     unsigned long cmd)
 {
+	u8 nr = _IOC_NR(cmd);
+
+	if (_IOC_DIR(cmd) != (_IOC_READ | _IOC_WRITE))
+		return -ENOIOCTLCMD;
+	if (_IOC_TYPE(cmd) != UVIO_TYPE_UVC)
+		return -ENOIOCTLCMD;
+	if (nr >= UVIO_IOCTL_NUM_IOCTLS)
+		return -ENOIOCTLCMD;
+	if (_IOC_SIZE(cmd) != sizeof(*ioctl))
+		return -ENOIOCTLCMD;
 	if (copy_from_user(ioctl, argp, sizeof(*ioctl)))
 		return -EFAULT;
 	if (ioctl->flags != 0)
@@ -194,7 +251,7 @@ static int uvio_copy_and_check_ioctl(struct uvio_ioctl_cb *ioctl, void __user *a
 	if (memchr_inv(ioctl->reserved14, 0, sizeof(ioctl->reserved14)))
 		return -EINVAL;
 
-	return 0;
+	return nr;
 }
 
 /*
@@ -205,12 +262,17 @@ static long uvio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	void __user *argp = (void __user *)arg;
 	struct uvio_ioctl_cb uv_ioctl = { };
 	long ret;
+	int nr;
+
+	nr = uvio_copy_and_check_ioctl(&uv_ioctl, argp, cmd);
+	if (nr < 0)
+		return nr;
 
-	switch (cmd) {
-	case UVIO_IOCTL_ATT:
-		ret = uvio_copy_and_check_ioctl(&uv_ioctl, argp);
-		if (ret)
-			return ret;
+	switch (nr) {
+	case UVIO_IOCTL_UVDEV_INFO_NR:
+		ret = uvio_uvdev_info(&uv_ioctl);
+		break;
+	case UVIO_IOCTL_ATT_NR:
 		ret = uvio_attestation(&uv_ioctl);
 		break;
 	default:
@@ -245,6 +307,7 @@ static void __exit uvio_dev_exit(void)
 
 static int __init uvio_dev_init(void)
 {
+	set_supp_uv_cmds(&uvdev_info);
 	return misc_register(&uvio_dev_miscdev);
 }
 
-- 
2.40.1