Extend VFIO_PCI_OFFSET_SHIFT to 48 to use the vfio-pci
VFIO_PCI_OFFSET_TO_INDEX() mechanism with the 256 TiB pseudo-BAR 0 of
the ISM device on s390. This bar is never mapped.
Acked-by: Alexandra Winter <wintera@linux.ibm.com>
Signed-off-by: Julian Ruess <julianr@linux.ibm.com>
---
drivers/vfio/pci/vfio_pci_core.c | 4 ++--
include/linux/vfio_pci_core.h | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
index 3a11e6f450f70105f17a3a621520c195d99e0671..3d70bf6668c7a69c4b46674195954d1ada662006 100644
--- a/drivers/vfio/pci/vfio_pci_core.c
+++ b/drivers/vfio/pci/vfio_pci_core.c
@@ -1647,7 +1647,7 @@ static unsigned long vma_to_pfn(struct vm_area_struct *vma)
u64 pgoff;
pgoff = vma->vm_pgoff &
- ((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
+ ((1UL << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
return (pci_resource_start(vdev->pdev, index) >> PAGE_SHIFT) + pgoff;
}
@@ -1751,7 +1751,7 @@ int vfio_pci_core_mmap(struct vfio_device *core_vdev, struct vm_area_struct *vma
phys_len = PAGE_ALIGN(pci_resource_len(pdev, index));
req_len = vma->vm_end - vma->vm_start;
pgoff = vma->vm_pgoff &
- ((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
+ ((1UL << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
req_start = pgoff << PAGE_SHIFT;
if (req_start + req_len > phys_len)
diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
index 1ac86896875cf5c9b5cc8ef25fae8bbd4394de05..12781707f086a330161990dc3579ec0d75887da8 100644
--- a/include/linux/vfio_pci_core.h
+++ b/include/linux/vfio_pci_core.h
@@ -20,7 +20,7 @@
#ifndef VFIO_PCI_CORE_H
#define VFIO_PCI_CORE_H
-#define VFIO_PCI_OFFSET_SHIFT 40
+#define VFIO_PCI_OFFSET_SHIFT 48
#define VFIO_PCI_OFFSET_TO_INDEX(off) (off >> VFIO_PCI_OFFSET_SHIFT)
#define VFIO_PCI_INDEX_TO_OFFSET(index) ((u64)(index) << VFIO_PCI_OFFSET_SHIFT)
#define VFIO_PCI_OFFSET_MASK (((u64)(1) << VFIO_PCI_OFFSET_SHIFT) - 1)
--
2.51.0Hi Julian,
kernel test robot noticed the following build warnings:
[auto build test WARNING on 05f7e89ab9731565d8a62e3b5d1ec206485eeb0b]
url: https://github.com/intel-lab-lkp/linux/commits/Julian-Ruess/vfio-pci-Set-VFIO_PCI_OFFSET_SHIFT-to-48/20260212-220938
base: 05f7e89ab9731565d8a62e3b5d1ec206485eeb0b
patch link: https://lore.kernel.org/r/20260212-vfio_pci_ism-v1-1-333262ade074%40linux.ibm.com
patch subject: [PATCH 1/3] vfio/pci: Set VFIO_PCI_OFFSET_SHIFT to 48
config: riscv-randconfig-001-20260213 (https://download.01.org/0day-ci/archive/20260213/202602130659.urh1Dx2i-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 11.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260213/202602130659.urh1Dx2i-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602130659.urh1Dx2i-lkp@intel.com/
All warnings (new ones prefixed by >>):
drivers/vfio/pci/nvgrace-gpu/main.c: In function 'addr_to_pgoff':
>> drivers/vfio/pci/nvgrace-gpu/main.c:196:22: warning: left shift count >= width of type [-Wshift-count-overflow]
196 | ((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
| ^~
drivers/vfio/pci/nvgrace-gpu/main.c: In function 'nvgrace_gpu_mmap':
drivers/vfio/pci/nvgrace-gpu/main.c:272:22: warning: left shift count >= width of type [-Wshift-count-overflow]
272 | ((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
| ^~
vim +196 drivers/vfio/pci/nvgrace-gpu/main.c
a23b10608d4203 Ankit Agrawal 2025-11-27 191
9db65489b87298 Ankit Agrawal 2025-11-27 192 static unsigned long addr_to_pgoff(struct vm_area_struct *vma,
9db65489b87298 Ankit Agrawal 2025-11-27 193 unsigned long addr)
9db65489b87298 Ankit Agrawal 2025-11-27 194 {
9db65489b87298 Ankit Agrawal 2025-11-27 195 u64 pgoff = vma->vm_pgoff &
9db65489b87298 Ankit Agrawal 2025-11-27 @196 ((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
9db65489b87298 Ankit Agrawal 2025-11-27 197
9db65489b87298 Ankit Agrawal 2025-11-27 198 return ((addr - vma->vm_start) >> PAGE_SHIFT) + pgoff;
9db65489b87298 Ankit Agrawal 2025-11-27 199 }
9db65489b87298 Ankit Agrawal 2025-11-27 200
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Hi Julian,
kernel test robot noticed the following build warnings:
[auto build test WARNING on 05f7e89ab9731565d8a62e3b5d1ec206485eeb0b]
url: https://github.com/intel-lab-lkp/linux/commits/Julian-Ruess/vfio-pci-Set-VFIO_PCI_OFFSET_SHIFT-to-48/20260212-220938
base: 05f7e89ab9731565d8a62e3b5d1ec206485eeb0b
patch link: https://lore.kernel.org/r/20260212-vfio_pci_ism-v1-1-333262ade074%40linux.ibm.com
patch subject: [PATCH 1/3] vfio/pci: Set VFIO_PCI_OFFSET_SHIFT to 48
config: powerpc-randconfig-002-20260213 (https://download.01.org/0day-ci/archive/20260213/202602130603.5vXcHBPj-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260213/202602130603.5vXcHBPj-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602130603.5vXcHBPj-lkp@intel.com/
All warnings (new ones prefixed by >>):
>> drivers/vfio/pci/vfio_pci_core.c:1646:28: warning: shift count >= width of type [-Wshift-count-overflow]
1646 | int index = vma->vm_pgoff >> (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT);
| ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/vfio/pci/vfio_pci_core.c:1650:9: warning: shift count >= width of type [-Wshift-count-overflow]
1650 | ((1UL << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
| ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/vfio/pci/vfio_pci_core.c:1701:22: warning: shift count >= width of type [-Wshift-count-overflow]
1701 | vma->vm_pgoff >>
| ^
1702 | (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT),
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/dev_printk.h:244:9: note: expanded from macro 'dev_dbg_ratelimited'
244 | ##__VA_ARGS__); \
| ^~~~~~~~~~~
drivers/vfio/pci/vfio_pci_core.c:1729:24: warning: shift count >= width of type [-Wshift-count-overflow]
1729 | index = vma->vm_pgoff >> (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT);
| ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/vfio/pci/vfio_pci_core.c:1754:9: warning: shift count >= width of type [-Wshift-count-overflow]
1754 | ((1UL << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
| ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
5 warnings generated.
vim +1646 drivers/vfio/pci/vfio_pci_core.c
abafbc551fdded drivers/vfio/pci/vfio_pci.c Alex Williamson 2020-04-22 1642
aac6db75a9fc2c drivers/vfio/pci/vfio_pci_core.c Alex Williamson 2024-05-29 1643 static unsigned long vma_to_pfn(struct vm_area_struct *vma)
11c4cd07ba111a drivers/vfio/pci/vfio_pci.c Alex Williamson 2020-04-28 1644 {
536475109c8284 drivers/vfio/pci/vfio_pci_core.c Max Gurtovoy 2021-08-26 1645 struct vfio_pci_core_device *vdev = vma->vm_private_data;
aac6db75a9fc2c drivers/vfio/pci/vfio_pci_core.c Alex Williamson 2024-05-29 @1646 int index = vma->vm_pgoff >> (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT);
aac6db75a9fc2c drivers/vfio/pci/vfio_pci_core.c Alex Williamson 2024-05-29 1647 u64 pgoff;
11c4cd07ba111a drivers/vfio/pci/vfio_pci.c Alex Williamson 2020-04-28 1648
aac6db75a9fc2c drivers/vfio/pci/vfio_pci_core.c Alex Williamson 2024-05-29 1649 pgoff = vma->vm_pgoff &
c298baab91b6e3 drivers/vfio/pci/vfio_pci_core.c Julian Ruess 2026-02-12 1650 ((1UL << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
aac6db75a9fc2c drivers/vfio/pci/vfio_pci_core.c Alex Williamson 2024-05-29 1651
aac6db75a9fc2c drivers/vfio/pci/vfio_pci_core.c Alex Williamson 2024-05-29 1652 return (pci_resource_start(vdev->pdev, index) >> PAGE_SHIFT) + pgoff;
11c4cd07ba111a drivers/vfio/pci/vfio_pci.c Alex Williamson 2020-04-28 1653 }
11c4cd07ba111a drivers/vfio/pci/vfio_pci.c Alex Williamson 2020-04-28 1654
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
On Thu, 12 Feb 2026 15:02:15 +0100 Julian Ruess <julianr@linux.ibm.com> wrote: > Extend VFIO_PCI_OFFSET_SHIFT to 48 to use the vfio-pci > VFIO_PCI_OFFSET_TO_INDEX() mechanism with the 256 TiB pseudo-BAR 0 of > the ISM device on s390. This bar is never mapped. Why does the entirety of vfio-pci need to adapt to the BAR requirements of this device? There's a variant driver included here that implements its own read/write handlers and doesn't support mmap, so you're already halfway there to implement your own region offsets independent of the conventions of the rest of vfio-pci. Thanks, Alex > Acked-by: Alexandra Winter <wintera@linux.ibm.com> > Signed-off-by: Julian Ruess <julianr@linux.ibm.com> > --- > drivers/vfio/pci/vfio_pci_core.c | 4 ++-- > include/linux/vfio_pci_core.h | 2 +- > 2 files changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c > index 3a11e6f450f70105f17a3a621520c195d99e0671..3d70bf6668c7a69c4b46674195954d1ada662006 100644 > --- a/drivers/vfio/pci/vfio_pci_core.c > +++ b/drivers/vfio/pci/vfio_pci_core.c > @@ -1647,7 +1647,7 @@ static unsigned long vma_to_pfn(struct vm_area_struct *vma) > u64 pgoff; > > pgoff = vma->vm_pgoff & > - ((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1); > + ((1UL << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1); > > return (pci_resource_start(vdev->pdev, index) >> PAGE_SHIFT) + pgoff; > } > @@ -1751,7 +1751,7 @@ int vfio_pci_core_mmap(struct vfio_device *core_vdev, struct vm_area_struct *vma > phys_len = PAGE_ALIGN(pci_resource_len(pdev, index)); > req_len = vma->vm_end - vma->vm_start; > pgoff = vma->vm_pgoff & > - ((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1); > + ((1UL << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1); > req_start = pgoff << PAGE_SHIFT; > > if (req_start + req_len > phys_len) > diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h > index 1ac86896875cf5c9b5cc8ef25fae8bbd4394de05..12781707f086a330161990dc3579ec0d75887da8 100644 > --- a/include/linux/vfio_pci_core.h > +++ b/include/linux/vfio_pci_core.h > @@ -20,7 +20,7 @@ > #ifndef VFIO_PCI_CORE_H > #define VFIO_PCI_CORE_H > > -#define VFIO_PCI_OFFSET_SHIFT 40 > +#define VFIO_PCI_OFFSET_SHIFT 48 > #define VFIO_PCI_OFFSET_TO_INDEX(off) (off >> VFIO_PCI_OFFSET_SHIFT) > #define VFIO_PCI_INDEX_TO_OFFSET(index) ((u64)(index) << VFIO_PCI_OFFSET_SHIFT) > #define VFIO_PCI_OFFSET_MASK (((u64)(1) << VFIO_PCI_OFFSET_SHIFT) - 1) >
On Thu, Feb 12, 2026 at 03:02:15PM +0100, Julian Ruess wrote: > Extend VFIO_PCI_OFFSET_SHIFT to 48 to use the vfio-pci > VFIO_PCI_OFFSET_TO_INDEX() mechanism with the 256 TiB pseudo-BAR 0 of > the ISM device on s390. This bar is never mapped. Woah, this is dangerous, the size was selected to fit within a pgoff of a 32bit system.. Does this entirely break vfio on 32 bit? Jason
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