linux-kernel - [PATCH RFC v2 3/5] vfio/virtio: add __always_inline for virtiovf_get_device_config

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Message-Id: <20250416-noautoinline-v2-3-e69a2717530f@uniontech.com>
Date: Wed, 16 Apr 2025 17:44:49 +0800
From: Chen Linxuan via B4 Relay <devnull+chenlinxuan.uniontech.com@...nel.org>
To: Keith Busch <kbusch@...nel.org>, Jens Axboe <axboe@...nel.dk>, 
 Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>, 
 Andrew Morton <akpm@...ux-foundation.org>, 
 Yishai Hadas <yishaih@...dia.com>, Jason Gunthorpe <jgg@...pe.ca>, 
 Shameer Kolothum <shameerali.kolothum.thodi@...wei.com>, 
 Kevin Tian <kevin.tian@...el.com>, 
 Alex Williamson <alex.williamson@...hat.com>, 
 Peter Huewe <peterhuewe@....de>, Jarkko Sakkinen <jarkko@...nel.org>, 
 Masahiro Yamada <masahiroy@...nel.org>, 
 Nathan Chancellor <nathan@...nel.org>, 
 Nicolas Schier <nicolas.schier@...ux.dev>, 
 Nick Desaulniers <nick.desaulniers+lkml@...il.com>, 
 Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>
Cc: linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 linux-mm@...ck.org, kvm@...r.kernel.org, virtualization@...ts.linux.dev, 
 linux-integrity@...r.kernel.org, linux-kbuild@...r.kernel.org, 
 llvm@...ts.linux.dev, Winston Wen <wentao@...ontech.com>, 
 Chen Linxuan <chenlinxuan@...ontech.com>, 
 Changbin Du <changbin.du@...el.com>
Subject: [PATCH RFC v2 3/5] vfio/virtio: add __always_inline for
 virtiovf_get_device_config_size

From: Winston Wen <wentao@...ontech.com>

Presume that kernel is compiled for x86_64 with gcc version 13.3.0:

  make defconfig
  ./scripts/kconfig/merge_config.sh .config <(
    echo CONFIG_VFIO=m
    echo CONFIG_VIRTIO_PCI=y
    echo CONFIG_VIRTIO_PCI_LIB_LEGACY=y
    echo CONFIG_VIRTIO_VFIO_PCI=m
    echo CONFIG_VIRTIO_VFIO_PCI_ADMIN_LEGACY=y
  )
  make KCFLAGS="-fno-inline-small-functions -fno-inline-functions-called-once" \
    drivers/vfio/pci/virtio/legacy_io.o

This results a compile error:

    CALL    scripts/checksyscalls.sh
    DESCEND objtool
    INSTALL libsubcmd_headers
    CC      drivers/vfio/pci/virtio/legacy_io.o
  In file included from <command-line>:
  drivers/vfio/pci/virtio/legacy_io.c: In function 'virtiovf_init_legacy_io':
  ././include/linux/compiler_types.h:557:45: error: call to '__compiletime_assert_889' declared with attribute error: BUILD_BUG_ON failed: !is_power_of_2(virtvdev->bar0_virtual_buf_size)
    557 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
        |                                             ^
  ././include/linux/compiler_types.h:538:25: note: in definition of macro '__compiletime_assert'
    538 |                         prefix ## suffix();                             \
        |                         ^~~~~~
  ././include/linux/compiler_types.h:557:9: note: in expansion of macro '_compiletime_assert'
    557 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
        |         ^~~~~~~~~~~~~~~~~~~
  ./include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
     39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
        |                                     ^~~~~~~~~~~~~~~~~~
  ./include/linux/build_bug.h:50:9: note: in expansion of macro 'BUILD_BUG_ON_MSG'
     50 |         BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
        |         ^~~~~~~~~~~~~~~~
  drivers/vfio/pci/virtio/legacy_io.c:401:9: note: in expansion of macro 'BUILD_BUG_ON'
    401 |         BUILD_BUG_ON(!is_power_of_2(virtvdev->bar0_virtual_buf_size));
        |         ^~~~~~~~~~~~

BUILD_BUG_ON needs virtvdev->bar0_virtual_buf_size to be computed at
compile time. So we should mark virtiovf_get_device_config_size() with
__always_inline here.

Co-developed-by: Chen Linxuan <chenlinxuan@...ontech.com>
Signed-off-by: Chen Linxuan <chenlinxuan@...ontech.com>
Signed-off-by: Winston Wen <wentao@...ontech.com>
---
 drivers/vfio/pci/virtio/legacy_io.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/vfio/pci/virtio/legacy_io.c b/drivers/vfio/pci/virtio/legacy_io.c
index 832af5ba267c49a079009cfe0fa93c15ba7a490f..b6871d50b9f9e278ef3c49a9cb2baf474b8271c6 100644
--- a/drivers/vfio/pci/virtio/legacy_io.c
+++ b/drivers/vfio/pci/virtio/legacy_io.c
@@ -350,7 +350,7 @@ int virtiovf_open_legacy_io(struct virtiovf_pci_core_device *virtvdev)
 	return virtiovf_set_notify_addr(virtvdev);
 }
 
-static int virtiovf_get_device_config_size(unsigned short device)
+static __always_inline int virtiovf_get_device_config_size(unsigned short device)
 {
 	/* Network card */
 	return offsetofend(struct virtio_net_config, status);

-- 
2.48.1