linux-kernel - [RFC] vDPA: Trying to make sense of config data

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Message-ID: <4f4572c8-1d8c-4ec6-96a1-fb74848475af@digitalocean.com>
Date: Thu, 22 Aug 2024 13:21:13 -0500
From: Carlos Bilbao <cbilbao@...italocean.com>
To: virtualization@...ts.linux-foundation.org, mst@...hat.com,
 jasowang@...hat.com
Cc: kvm@...r.kernel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC] vDPA: Trying to make sense of config data

Hello folks,

I'm using the code below to retrieve configuration data for my vDPA file
via ioctl. I get as output:

Configuration data (24 bytes):
5a c3 5f 68 48 a9 01 00 08 00 dc 05 00 00 00 00
00 00 00 00 00 00 00 00
ASCII representation:
Z._hH...................

Could a good Samaritan point me in the right direction for the docs I need
to understand these values and convert them to a human-readable format?
hank you in advance!

Regards,
Carlos

---

void check_config(int fd) {

    uint32_t size;
    struct vhost_vdpa_config *config;
    uint8_t *buf;

    if (ioctl(fd, VHOST_VDPA_GET_CONFIG_SIZE, &size) < 0) {
        perror("ioctl failed");
        return;
    }

    config = malloc(sizeof(struct vhost_vdpa_config) + size);
    if (!config) {
        perror("malloc failed");
        return;
    }

    memset(config, 0, sizeof(struct vhost_vdpa_config) + size);
    config->len = size;
    config->off = 0;

    buf = config->buf;

    if (ioctl(fd, VHOST_VDPA_GET_CONFIG, config) < 0) {
        perror("ioctl failed");
    } else {
        printf("Configuration data (%u bytes):\n", size);

        /* Print the data in a human-readable format */
        for (unsigned int i = 0; i < size; i++) {
            if (i % 16 == 0 && i != 0) printf("\n");
            printf("%02x ", buf[i]);
        }
        printf("\n");

        printf("ASCII representation:\n");
        for (unsigned int i = 0; i < size; i++) {
            if (buf[i] >= 32 && buf[i] <= 126) {
                printf("%c", buf[i]);
            } else {
                printf(".");
            }
        }
        printf("\n");
    }

    free(config);
}