Re: [Qemu-devel] [PATCH v6 3/6] Qemu-Xen-vTPM: Xen frontend driver infrastructure

[Stefano Stabellini]

On Mon, 4 May 2015, Quan Xu wrote:
> This patch adds infrastructure for xen front drivers living in qemu,
> so drivers don't need to implement common stuff on their own.  It's
> mostly xenbus management stuff: some functions to access XenStore,
> setting up XenStore watches, callbacks on device discovery and state
> changes, and handle event channel between the virtual machines.
> 
> Call xen_fe_register() function to register XenDevOps, and make sure,
>          [...]
>     3 = ""
>      [...]
>      device = "" (frontend device, the backend is running in QEMU/.etc)
>       vkbd = ""
>        [...]
>       vif = ""
>        [...]
> 
>  ..
> 
> (QEMU) xen_vtpmdev_ops is initialized with the following process:
>   xen_hvm_init()
>     [...]
>     -->xen_fe_register("vtpm", ...)
>       -->xenstore_fe_scan()
>         -->xen_fe_try_init(ops)
>           --> XenDevOps.init()
>         -->xen_fe_get_xendev()
>           --> XenDevOps.alloc()
>         -->xen_fe_check()
>           -->xen_fe_try_initialise()
>             --> XenDevOps.initialise()
>           -->xen_fe_try_connected()
>             --> XenDevOps.connected()
>         -->xs_watch()
>     [...]
> 
> Signed-off-by: Quan Xu <address@hidden>
> 
> --Changes in v6:
>  -Replace buf_size with PAGE_SIZE and use length rather than
>   shr->length.
> ---
>  hw/tpm/Makefile.objs         |   1 +
>  hw/tpm/xen_vtpm_frontend.c   | 315 
> +++++++++++++++++++++++++++++++++++++++++++
>  hw/xen/xen_frontend.c        |  20 +++
>  include/hw/xen/xen_backend.h |   5 +
>  include/hw/xen/xen_common.h  |   6 +
>  xen-hvm.c                    |   5 +
>  6 files changed, 352 insertions(+)
>  create mode 100644 hw/tpm/xen_vtpm_frontend.c
> 
> diff --git a/hw/tpm/Makefile.objs b/hw/tpm/Makefile.objs
> index 99f5983..57919fa 100644
> --- a/hw/tpm/Makefile.objs
> +++ b/hw/tpm/Makefile.objs
> @@ -1,2 +1,3 @@
>  common-obj-$(CONFIG_TPM_TIS) += tpm_tis.o
>  common-obj-$(CONFIG_TPM_PASSTHROUGH) += tpm_passthrough.o
> +common-obj-$(CONFIG_TPM_XENSTUBDOMS) += xen_vtpm_frontend.o
> diff --git a/hw/tpm/xen_vtpm_frontend.c b/hw/tpm/xen_vtpm_frontend.c
> new file mode 100644
> index 0000000..d6e7cc6
> --- /dev/null
> +++ b/hw/tpm/xen_vtpm_frontend.c
> @@ -0,0 +1,315 @@
> +/*
> + * Connect to Xen vTPM stubdom domain
> + *
> + *  Copyright (c) 2015 Intel Corporation
> + *  Authors:
> + *    Quan Xu <address@hidden>
> + *
> + * This library is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU Lesser General Public
> + * License as published by the Free Software Foundation; either
> + * version 2 of the License, or (at your option) any later version.
> + *
> + * This library is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> + * Lesser General Public License for more details.
> + *
> + * You should have received a copy of the GNU Lesser General Public
> + * License along with this library; if not, see 
> <http://www.gnu.org/licenses/>
> + */
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <stdarg.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include <signal.h>
> +#include <inttypes.h>
> +#include <time.h>
> +#include <fcntl.h>
> +#include <errno.h>
> +#include <sys/ioctl.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <sys/mman.h>
> +#include <sys/uio.h>
> +
> +#include "hw/hw.h"
> +#include "block/aio.h"
> +#include "hw/xen/xen_backend.h"
> +
> +#ifndef XS_STUBDOM_VTPM_ENABLE
> +#define XS_STUBDOM_VTPM_ENABLE    "1"
> +#endif
> +
> +#ifndef PAGE_SIZE
> +#define PAGE_SIZE      4096
> +#endif
> +
> +enum tpmif_state {
> +    /* No contents, vTPM idle, cancel complete */
> +    TPMIF_STATE_IDLE,
> +    /* Request ready or vTPM working */
> +    TPMIF_STATE_SUBMIT,
> +    /* Response ready or vTPM idle */
> +    TPMIF_STATE_FINISH,
> +    /* Cancel requested or vTPM working */
> +    TPMIF_STATE_CANCEL,
> +};
> +
> +static AioContext *vtpm_aio_ctx;
> +
> +enum status_bits {
> +    VTPM_STATUS_RUNNING  = 0x1,
> +    VTPM_STATUS_IDLE     = 0x2,
> +    VTPM_STATUS_RESULT   = 0x4,
> +    VTPM_STATUS_CANCELED = 0x8,
> +};
> +
> +struct tpmif_shared_page {
> +    /* Request and response length in bytes */
> +    uint32_t length;
> +    /* Enum tpmif_state */
> +    uint8_t  state;
> +    /* For the current request */
> +    uint8_t  locality;
> +    /* Should be zero */
> +    uint8_t  pad;
> +    /* Extra pages for long packets; may be zero */
> +    uint8_t  nr_extra_pages;
> +    /*
> +     * Grant IDs, the length is actually nr_extra_pages.
> +     * beyond the extra_pages entries is the actual request
> +     * and response.
> +     */
> +    uint32_t extra_pages[0];
> +};
> +
> +struct xen_vtpm_dev {
> +    struct XenDevice xendev;  /* must be first */
> +    struct           tpmif_shared_page *shr;
> +    xc_gntshr        *xen_xcs;
> +    int              ring_ref;
> +    int              bedomid;
> +    QEMUBH           *sr_bh;
> +};
> +
> +static uint8_t vtpm_status(struct xen_vtpm_dev *vtpmdev)
> +{
> +    switch (vtpmdev->shr->state) {
> +    case TPMIF_STATE_IDLE:
> +    case TPMIF_STATE_FINISH:
> +        return VTPM_STATUS_IDLE;
> +    case TPMIF_STATE_SUBMIT:
> +    case TPMIF_STATE_CANCEL:
> +        return VTPM_STATUS_RUNNING;
> +    default:
> +        return 0;
> +    }
> +}
> +
> +static bool vtpm_aio_wait(AioContext *ctx)
> +{
> +    return aio_poll(ctx, true);
> +}
> +
> +static void sr_bh_handler(void *opaque)
> +{
> +}
> +
> +int vtpm_recv(struct XenDevice *xendev, uint8_t* buf, size_t *count)
> +{
> +    struct xen_vtpm_dev *vtpmdev = container_of(xendev, struct xen_vtpm_dev,
> +                                                xendev);
> +    struct tpmif_shared_page *shr = vtpmdev->shr;
> +    unsigned int offset;
> +    size_t length = shr->length;
> +
> +    if (shr->state == TPMIF_STATE_IDLE) {
> +        return -ECANCELED;
> +    }
> +
> +    offset = sizeof(*shr) + sizeof(shr->extra_pages[0])*shr->nr_extra_pages;
> +    if (offset > PAGE_SIZE) {
> +        return -EIO;
> +    }
> +
> +    if (offset + length > PAGE_SIZE) {
> +        length = PAGE_SIZE - offset;
> +    }
> +
> +    memcpy(buf, offset + (uint8_t *)shr, length);
> +    *count = length;
> +
> +    return 0;
> +}
> +
> +int vtpm_send(struct XenDevice *xendev, uint8_t* buf, size_t count)
> +{
> +    struct xen_vtpm_dev *vtpmdev = container_of(xendev, struct xen_vtpm_dev,
> +                                                xendev);
> +    struct tpmif_shared_page *shr = vtpmdev->shr;
> +    unsigned int offset = sizeof(*shr) +
> +                          sizeof(shr->extra_pages[0])*shr->nr_extra_pages;
> +
> +    if (offset > PAGE_SIZE) {
> +        return -EIO;
> +    }
> +
> +    if (offset + count > PAGE_SIZE) {
> +        return -ECANCELED;
> +    }
> +
> +    while (vtpm_status(vtpmdev) != VTPM_STATUS_IDLE) {
> +        vtpm_aio_wait(vtpm_aio_ctx);
> +    }
> +
> +    memcpy(offset + (uint8_t *)shr, buf, count);
> +    shr->length = count;
> +    barrier();
> +    shr->state = TPMIF_STATE_SUBMIT;
> +    xen_wmb();
> +    xen_be_send_notify(&vtpmdev->xendev);
> +
> +    while (vtpm_status(vtpmdev) != VTPM_STATUS_IDLE) {
> +        vtpm_aio_wait(vtpm_aio_ctx);
> +    }
> +
> +    return count;
> +}
> +
> +static int vtpm_initialise(struct XenDevice *xendev)
> +{
> +    struct xen_vtpm_dev *vtpmdev = container_of(xendev, struct xen_vtpm_dev,
> +                                                xendev);
> +    xs_transaction_t xbt = XBT_NULL;
> +    unsigned int ring_ref;
> +
> +    vtpmdev->xendev.fe = xenstore_read_be_str(&vtpmdev->xendev, "frontend");
> +    if (vtpmdev->xendev.fe == NULL) {
> +        return -1;
> +    }
> +
> +    /* Get backend domid */
> +    if (xenstore_read_fe_int(&vtpmdev->xendev, "backend-id",
> +                             &vtpmdev->bedomid)) {
> +        return -1;
> +    }
> +
> +    /* Alloc shared page */
> +    vtpmdev->shr = xc_gntshr_share_pages(vtpmdev->xen_xcs, vtpmdev->bedomid, 
> 1,
> +                                         &ring_ref, PROT_READ|PROT_WRITE);
> +    vtpmdev->ring_ref = ring_ref;
> +    if (vtpmdev->shr == NULL) {
> +        return -1;
> +    }
> +
> +    /* Create event channel */
> +    if (xen_fe_alloc_unbound(&vtpmdev->xendev, 0, vtpmdev->bedomid)) {
> +        xc_gntshr_munmap(vtpmdev->xen_xcs, vtpmdev->shr, 1);
> +        return -1;
> +    }
> +
> +    xc_evtchn_unmask(vtpmdev->xendev.evtchndev,
> +                     vtpmdev->xendev.local_port);
> +
> +again:
> +    xbt = xs_transaction_start(xenstore);
> +    if (xbt == XBT_NULL) {
> +        goto abort_transaction;
> +    }
> +
> +    if (xenstore_write_int(vtpmdev->xendev.fe, "ring-ref",
> +                           vtpmdev->ring_ref)) {
> +        goto abort_transaction;
> +    }
> +
> +    if (xenstore_write_int(vtpmdev->xendev.fe, "event-channel",
> +                           vtpmdev->xendev.local_port)) {
> +        goto abort_transaction;
> +    }
> +
> +    /* Publish protocol v2 feature */
> +    if (xenstore_write_int(vtpmdev->xendev.fe, "feature-protocol-v2", 1)) {
> +        goto abort_transaction;
> +    }
> +
> +    if (!xs_transaction_end(xenstore, xbt, 0)) {
> +        if (errno == EAGAIN) {
> +            goto again;
> +        }
> +    }
> +
> +    return 0;
> +
> +abort_transaction:
> +    xc_gntshr_munmap(vtpmdev->xen_xcs, vtpmdev->shr, 1);
> +    xs_transaction_end(xenstore, xbt, 1);
> +    return -1;
> +}
> +
> +static int vtpm_free(struct XenDevice *xendev)
> +{
> +    struct xen_vtpm_dev *vtpmdev = container_of(xendev, struct xen_vtpm_dev,
> +                                                xendev);
> +
> +    aio_poll(vtpm_aio_ctx, false);
> +    qemu_bh_delete(vtpmdev->sr_bh);
> +    if (vtpmdev->shr) {
> +        xc_gntshr_munmap(vtpmdev->xen_xcs, vtpmdev->shr, 1);
> +    }
> +    xc_interface_close(vtpmdev->xen_xcs);
> +    return 0;
> +}
> +
> +static int vtpm_init(struct XenDevice *xendev)
> +{
> +    char path[XEN_BUFSIZE];
> +    char *value;
> +    unsigned int stubdom_vtpm = 0;
> +
> +    snprintf(path, sizeof(path), 
> "/local/domain/%d/platform/acpi_stubdom_vtpm",
> +             xen_domid);
> +    value = xs_read(xenstore, 0, path, &stubdom_vtpm);
> +    if (stubdom_vtpm <= 0 || strcmp(value, XS_STUBDOM_VTPM_ENABLE)) {
> +        free(value);
> +        return -1;
> +    }
> +    free(value);
> +    return 0;
> +}
> +
> +static void vtpm_alloc(struct XenDevice *xendev)
> +{
> +    struct xen_vtpm_dev *vtpmdev = container_of(xendev, struct xen_vtpm_dev,
> +                                                xendev);
> +
> +    vtpm_aio_ctx = aio_context_new(NULL);
> +    if (vtpm_aio_ctx == NULL) {
> +        return;
> +    }
> +    vtpmdev->sr_bh = aio_bh_new(vtpm_aio_ctx, sr_bh_handler, vtpmdev);
> +    qemu_bh_schedule(vtpmdev->sr_bh);
> +    vtpmdev->xen_xcs = xen_xc_gntshr_open(0, 0);
> +}
> +
> +static void vtpm_event(struct XenDevice *xendev)
> +{
> +    struct xen_vtpm_dev *vtpmdev = container_of(xendev, struct xen_vtpm_dev,
> +                                                xendev);
> +
> +    qemu_bh_schedule(vtpmdev->sr_bh);
> +}
> +
> +struct XenDevOps xen_vtpmdev_ops = {
> +    .size             = sizeof(struct xen_vtpm_dev),
> +    .flags            = DEVOPS_FLAG_IGNORE_STATE |
> +                        DEVOPS_FLAG_FE,
> +    .event            = vtpm_event,
> +    .free             = vtpm_free,
> +    .init             = vtpm_init,
> +    .alloc            = vtpm_alloc,
> +    .initialise       = vtpm_initialise,
> +    .backend_changed  = vtpm_backend_changed,
> +};
> diff --git a/hw/xen/xen_frontend.c b/hw/xen/xen_frontend.c
> index 55af45a..1ca7342 100644
> --- a/hw/xen/xen_frontend.c
> +++ b/hw/xen/xen_frontend.c
> @@ -60,6 +60,26 @@ static void xen_fe_evtchn_event(void *opaque)
>  
>  /* ------------------------------------------------------------- */
>  
> +void vtpm_backend_changed(struct XenDevice *xendev, const char *node)
> +{
> +    int be_state;
> +
> +    if (strcmp(node, "state") == 0) {
> +        xenstore_read_be_int(xendev, node, &be_state);
> +        switch (be_state) {
> +        case XenbusStateConnected:
> +            /* TODO */
> +            break;
> +        case XenbusStateClosing:
> +        case XenbusStateClosed:
> +            xenbus_switch_state(xendev, XenbusStateClosing);
> +            break;
> +        default:
> +            break;
> +        }
> +    }
> +}

If this function is vtpm specific, it should be moved to
hw/tpm/xen_vtpm_frontend.c, where the vtpm frontend driver lives.


>  int xen_fe_alloc_unbound(struct XenDevice *xendev, int dom, int remote_dom)
>  {
>      xendev->local_port = xc_evtchn_bind_unbound_port(xendev->evtchndev,
> diff --git a/include/hw/xen/xen_backend.h b/include/hw/xen/xen_backend.h
> index bb0b303..b959413 100644
> --- a/include/hw/xen/xen_backend.h
> +++ b/include/hw/xen/xen_backend.h
> @@ -110,6 +110,11 @@ int xen_fe_register(const char *type, struct XenDevOps 
> *ops);
>  int xen_fe_alloc_unbound(struct XenDevice *xendev, int dom, int remote_dom);
>  int xenbus_switch_state(struct XenDevice *xendev, enum xenbus_state xbus);
>  
> +/* Xen vtpm */
> +int vtpm_send(struct XenDevice *xendev, uint8_t* buf, size_t count);
> +int vtpm_recv(struct XenDevice *xendev, uint8_t* buf, size_t *count);
> +void vtpm_backend_changed(struct XenDevice *xendev, const char *node);

Then you don't need this anymore.


>  /* actual backend drivers */
>  extern struct XenDevOps xen_console_ops;      /* xen_console.c     */
>  extern struct XenDevOps xen_kbdmouse_ops;     /* xen_framebuffer.c */
> diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
> index 38f29fb..7268d0c 100644
> --- a/include/hw/xen/xen_common.h
> +++ b/include/hw/xen/xen_common.h
> @@ -132,6 +132,12 @@ static inline XenXC xen_xc_interface_open(void *logger, 
> void *dombuild_logger,
>      return xc_interface_open(logger, dombuild_logger, open_flags);
>  }
>  
> +static inline xc_gntshr *xen_xc_gntshr_open(void *logger,
> +                                            unsigned int open_flags)
> +{
> +    return xc_gntshr_open(logger, open_flags);
> +}
> +
>  /* FIXME There is now way to have the xen fd */
>  static inline int xc_fd(xc_interface *xen_xc)
>  {
> diff --git a/xen-hvm.c b/xen-hvm.c
> index 315864c..b2403dc 100644
> --- a/xen-hvm.c
> +++ b/xen-hvm.c
> @@ -1308,6 +1308,11 @@ int xen_hvm_init(ram_addr_t *below_4g_mem_size, 
> ram_addr_t *above_4g_mem_size,
>          fprintf(stderr, "%s: xen backend core setup failed\n", __FUNCTION__);
>          return -1;
>      }
> +
> +#ifdef CONFIG_TPM_XENSTUBDOMS
> +    xen_fe_register("vtpm", &xen_vtpmdev_ops);
> +#endif
> +
>      xen_be_register("console", &xen_console_ops);
>      xen_be_register("vkbd", &xen_kbdmouse_ops);
>      xen_be_register("qdisk", &xen_blkdev_ops);
> -- 
> 1.8.3.2
>