Messages in this thread | | | Subject | Re: [PATCH v9 09/22] s390: vfio-ap: register matrix device with VFIO mdev framework | From | Tony Krowiak <> | Date | Thu, 16 Aug 2018 12:24:16 -0400 |
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On 08/14/2018 07:19 AM, Cornelia Huck wrote: > On Mon, 13 Aug 2018 17:48:06 -0400 > Tony Krowiak <akrowiak@linux.vnet.ibm.com> wrote: > >> From: Tony Krowiak <akrowiak@linux.ibm.com> >> >> Registers the matrix device created by the VFIO AP device >> driver with the VFIO mediated device framework. >> Registering the matrix device will create the sysfs >> structures needed to create mediated matrix devices >> each of which will be used to configure the AP matrix >> for a guest and connect it to the VFIO AP device driver. >> >> Registering the matrix device with the VFIO mediated device >> framework will create the following sysfs structures: >> >> /sys/devices/vfio_ap/matrix/ >> ...... [mdev_supported_types] >> ......... [vfio_ap-passthrough] >> ............ create >> >> To create a mediated device for the AP matrix device, write a UUID >> to the create file: >> >> uuidgen > create >> >> A symbolic link to the mediated device's directory will be created in the >> devices subdirectory named after the generated $uuid: >> >> /sys/devices/vfio_ap/matrix/ >> ...... [mdev_supported_types] >> ......... [vfio_ap-passthrough] >> ............ [devices] >> ............... [$uuid] >> >> A symbolic link to the mediated device will also be created >> in the vfio_ap matrix's directory: >> >> /sys/devices/vfio_ap/matrix/[$uuid] >> >> Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> >> Reviewed-by: Halil Pasic <pasic@linux.ibm.com> >> Tested-by: Michael Mueller <mimu@linux.ibm.com> >> Tested-by: Farhan Ali <alifm@linux.ibm.com> >> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com> >> --- >> MAINTAINERS | 1 + >> drivers/s390/crypto/Makefile | 2 +- >> drivers/s390/crypto/vfio_ap_drv.c | 23 ++++++ >> drivers/s390/crypto/vfio_ap_ops.c | 124 +++++++++++++++++++++++++++++++++ >> drivers/s390/crypto/vfio_ap_private.h | 45 ++++++++++++ >> include/uapi/linux/vfio.h | 1 + >> 6 files changed, 195 insertions(+), 1 deletions(-) >> create mode 100644 drivers/s390/crypto/vfio_ap_ops.c >> > >> diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c >> new file mode 100644 >> index 0000000..8018c2d >> --- /dev/null >> +++ b/drivers/s390/crypto/vfio_ap_ops.c >> @@ -0,0 +1,124 @@ >> +// SPDX-License-Identifier: GPL-2.0+ >> +/* >> + * Adjunct processor matrix VFIO device driver callbacks. >> + * >> + * Copyright IBM Corp. 2018 >> + * >> + * Author(s): Tony Krowiak <akrowiak@linux.ibm.com> >> + * Halil Pasic <pasic@linux.ibm.com> >> + * Pierre Morel <pmorel@linux.ibm.com> >> + */ >> +#include <linux/string.h> >> +#include <linux/vfio.h> >> +#include <linux/device.h> >> +#include <linux/list.h> >> +#include <linux/ctype.h> >> + >> +#include "vfio_ap_private.h" >> + >> +#define VFIO_AP_MDEV_TYPE_HWVIRT "passthrough" >> +#define VFIO_AP_MDEV_NAME_HWVIRT "VFIO AP Passthrough Device" >> + >> +static void vfio_ap_matrix_init(struct ap_config_info *info, >> + struct ap_matrix *matrix) >> +{ >> + matrix->apm_max = info->apxa ? info->Na : 63; >> + matrix->aqm_max = info->apxa ? info->Nd : 15; >> + matrix->adm_max = info->apxa ? info->Nd : 15; >> +} >> + >> +static int vfio_ap_mdev_create(struct kobject *kobj, struct mdev_device *mdev) >> +{ >> + struct ap_matrix_mdev *matrix_mdev; >> + >> + matrix_mdev = kzalloc(sizeof(*matrix_mdev), GFP_KERNEL); >> + if (!matrix_mdev) >> + return -ENOMEM; >> + >> + matrix_mdev->name = dev_name(mdev_dev(mdev)); >> + vfio_ap_matrix_init(&matrix_dev.info, &matrix_mdev->matrix); >> + mdev_set_drvdata(mdev, matrix_mdev); >> + >> + if (atomic_dec_if_positive(&matrix_dev.available_instances) < 0) { >> + kfree(matrix_mdev); >> + return -EPERM; >> + } > Maybe move this check to the top of the function?
Please ignore my previous response to your comment. I can't move the call to atomic_dec_if_positive() to the top of the function because it decrements the available_instances and if the kzalloc() of matrix_mdev fails, then the value would have to then be incremented to remain valid. What I can do is this:
1. Check the value of available_instances using atomic_read() at the top of the function and if it is zero, return an error.
2. Replace the call to atomic_dec_if_positive() with a call to atomic_dec() to decrement the available_instances.
I agree that it makes sense to return before attempting to allocate the matrix_mdev if available_instances is zero.
> >> + >> + mutex_lock(&matrix_dev.lock); >> + list_add(&matrix_mdev->list, &matrix_dev.mdev_list); >> + mutex_unlock(&matrix_dev.lock); >> + >> + return 0; >> +}
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