vfio/pci: Use bitfield for struct vfio_pci_core_device flags

struct vfio_pci_core_device contains eleven boolean flags.
Boolean flags clearly indicate their usage but space usage
starts to be a concern when there are many.

An upcoming change adds another boolean flag to
struct vfio_pci_core_device, thereby increasing the concern
that the boolean flags are consuming unnecessary space.

Transition the boolean flags to use bitfields. On a system that
uses one byte per boolean this reduces the space consumed
by existing flags from 11 bytes to 2 bytes with room for
a few more flags without increasing the structure's size.

Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://lore.kernel.org/r/cf34bf0499c889554a8105eeb18cc0ab673005be.1683740667.git.reinette.chatre@intel.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
index 148fd1ae6c1c43e6e09a4cbb4b08b18872f50851..adb47e2914d7451293cadaee43f0c4a4225e057c 100644 (file)
--- a/include/linux/vfio_pci_core.h
+++ b/include/linux/vfio_pci_core.h
@@ -68,17 +68,17 @@ struct vfio_pci_core_device {
        u16                     msix_size;
        u32                     msix_offset;
        u32                     rbar[7];
-       bool                    pci_2_3;
-       bool                    virq_disabled;
-       bool                    reset_works;
-       bool                    extended_caps;
-       bool                    bardirty;
-       bool                    has_vga;
-       bool                    needs_reset;
-       bool                    nointx;
-       bool                    needs_pm_restore;
-       bool                    pm_intx_masked;
-       bool                    pm_runtime_engaged;
+       bool                    pci_2_3:1;
+       bool                    virq_disabled:1;
+       bool                    reset_works:1;
+       bool                    extended_caps:1;
+       bool                    bardirty:1;
+       bool                    has_vga:1;
+       bool                    needs_reset:1;
+       bool                    nointx:1;
+       bool                    needs_pm_restore:1;
+       bool                    pm_intx_masked:1;
+       bool                    pm_runtime_engaged:1;
        struct pci_saved_state  *pci_saved_state;
        struct pci_saved_state  *pm_save;
        int                     ioeventfds_nr;