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    SubjectRe: [PATCH v2 1/2] KVM: Start populating /sys/hypervisor with KVM entries
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    On 14.05.19 17:16, Filippo Sironi wrote:
    > Start populating /sys/hypervisor with KVM entries when we're running on
    > KVM. This is to replicate functionality that's available when we're
    > running on Xen.
    >
    > Start with /sys/hypervisor/uuid, which users prefer over
    > /sys/devices/virtual/dmi/id/product_uuid as a way to recognize a virtual
    > machine, since it's also available when running on Xen HVM and on Xen PV
    > and, on top of that doesn't require root privileges by default.
    > Let's create arch-specific hooks so that different architectures can
    > provide different implementations.
    >
    > Signed-off-by: Filippo Sironi <sironi@amazon.de>
    > ---
    > v2:
    > * move the retrieval of the VM UUID out of uuid_show and into
    > kvm_para_get_uuid, which is a weak function that can be overwritten
    >
    > drivers/Kconfig | 2 ++
    > drivers/Makefile | 2 ++
    > drivers/kvm/Kconfig | 14 ++++++++++++++
    > drivers/kvm/Makefile | 1 +
    > drivers/kvm/sys-hypervisor.c | 30 ++++++++++++++++++++++++++++++
    > 5 files changed, 49 insertions(+)
    > create mode 100644 drivers/kvm/Kconfig
    > create mode 100644 drivers/kvm/Makefile
    > create mode 100644 drivers/kvm/sys-hypervisor.c
    >
    > diff --git a/drivers/Kconfig b/drivers/Kconfig
    > index 45f9decb9848..90eb835fe951 100644
    > --- a/drivers/Kconfig
    > +++ b/drivers/Kconfig
    > @@ -146,6 +146,8 @@ source "drivers/hv/Kconfig"
    >
    > source "drivers/xen/Kconfig"
    >
    > +source "drivers/kvm/Kconfig"
    > +
    > source "drivers/staging/Kconfig"
    >
    > source "drivers/platform/Kconfig"
    > diff --git a/drivers/Makefile b/drivers/Makefile
    > index c61cde554340..79cc92a3f6bf 100644
    > --- a/drivers/Makefile
    > +++ b/drivers/Makefile
    > @@ -44,6 +44,8 @@ obj-y += soc/
    > obj-$(CONFIG_VIRTIO) += virtio/
    > obj-$(CONFIG_XEN) += xen/
    >
    > +obj-$(CONFIG_KVM_GUEST) += kvm/
    > +
    > # regulators early, since some subsystems rely on them to initialize
    > obj-$(CONFIG_REGULATOR) += regulator/
    >
    > diff --git a/drivers/kvm/Kconfig b/drivers/kvm/Kconfig
    > new file mode 100644
    > index 000000000000..3fc041df7c11
    > --- /dev/null
    > +++ b/drivers/kvm/Kconfig
    > @@ -0,0 +1,14 @@
    > +menu "KVM driver support"
    > + depends on KVM_GUEST
    > +
    > +config KVM_SYS_HYPERVISOR
    > + bool "Create KVM entries under /sys/hypervisor"
    > + depends on SYSFS
    > + select SYS_HYPERVISOR
    > + default y
    > + help
    > + Create KVM entries under /sys/hypervisor (e.g., uuid). When running
    > + native or on another hypervisor, /sys/hypervisor may still be
    > + present, but it will have no KVM entries.
    > +
    > +endmenu
    > diff --git a/drivers/kvm/Makefile b/drivers/kvm/Makefile
    > new file mode 100644
    > index 000000000000..73a43fc994b9
    > --- /dev/null
    > +++ b/drivers/kvm/Makefile
    > @@ -0,0 +1 @@
    > +obj-$(CONFIG_KVM_SYS_HYPERVISOR) += sys-hypervisor.o
    > diff --git a/drivers/kvm/sys-hypervisor.c b/drivers/kvm/sys-hypervisor.c
    > new file mode 100644
    > index 000000000000..43b1d1a09807
    > --- /dev/null
    > +++ b/drivers/kvm/sys-hypervisor.c
    > @@ -0,0 +1,30 @@
    > +/* SPDX-License-Identifier: GPL-2.0 */
    > +
    > +#include <asm/kvm_para.h>
    > +
    > +#include <linux/kobject.h>
    > +#include <linux/sysfs.h>
    > +
    > +__weak const char *kvm_para_get_uuid(void)
    > +{
    > + return NULL;
    > +}
    > +
    > +static ssize_t uuid_show(struct kobject *obj,
    > + struct kobj_attribute *attr,
    > + char *buf)
    > +{
    > + const char *uuid = kvm_para_get_uuid();

    I would prefer to have kvm_para_get_uuid return a uuid_t
    but char * will probably work out as well.


    > + return sprintf(buf, "%s\n", uuid);
    > +}
    > +
    > +static struct kobj_attribute uuid = __ATTR_RO(uuid);
    > +
    > +static int __init uuid_init(void)
    > +{
    > + if (!kvm_para_available())

    Isnt kvm_para_available a function that is defined in the context of the HOST
    and not of the guest?

    > + return 0;
    > + return sysfs_create_file(hypervisor_kobj, &uuid.attr);
    > +}
    > +
    > +device_initcall(uuid_init);
    >

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