Re: [PATCH v3 2/3] vfio/pci: Support 8-byte PCI loads and stores

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On 4/25/2024 9:56 AM, Gerd Bayer wrote:
From: Ben Segal <bpsegal@xxxxxxxxxx>

Many PCI adapters can benefit or even require full 64bit read
and write access to their registers. In order to enable work on
user-space drivers for these devices add two new variations
vfio_pci_core_io{read|write}64 of the existing access methods
when the architecture supports 64-bit ioreads and iowrites.

This is indeed necessary as back to back 32 bit may not be optimal in some devices.

Signed-off-by: Ben Segal <bpsegal@xxxxxxxxxx>
Co-developed-by: Gerd Bayer <gbayer@xxxxxxxxxxxxx>
Signed-off-by: Gerd Bayer <gbayer@xxxxxxxxxxxxx>
  drivers/vfio/pci/vfio_pci_rdwr.c | 16 ++++++++++++++++
  include/linux/vfio_pci_core.h    |  3 +++
  2 files changed, 19 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
index 3335f1b868b1..8ed06edaee23 100644
--- a/drivers/vfio/pci/vfio_pci_rdwr.c
+++ b/drivers/vfio/pci/vfio_pci_rdwr.c
@@ -89,6 +89,9 @@ EXPORT_SYMBOL_GPL(vfio_pci_core_ioread##size);
+#ifdef ioread64
#define VFIO_IORDWR(size) \
  static int vfio_pci_core_iordwr##size(struct vfio_pci_core_device *vdev,\
@@ -124,6 +127,10 @@ static int vfio_pci_core_iordwr##size(struct vfio_pci_core_device *vdev,\
+#if defined(ioread64) && defined(iowrite64)
   * Read or write from an __iomem region (MMIO or I/O port) with an excluded
   * range which is inaccessible.  The excluded range drops writes and fills
@@ -148,6 +155,15 @@ ssize_t vfio_pci_core_do_io_rw(struct vfio_pci_core_device *vdev, bool test_mem,
  			fillable = 0;
+#if defined(ioread64) && defined(iowrite64)

Can we check for #ifdef CONFIG_64BIT instead? In x86, ioread64 and iowrite64 get declared as extern functions if CONFIG_GENERIC_IOMAP is defined and this check always fails. In include/asm-generic/io.h, asm-generic/iomap.h gets included which declares them as extern functions.

One more thing to consider io-64-nonatomic-hi-lo.h and io-64-nonatomic-lo-hi.h, if included would define it as a macro that calls a function that rw 32 bits back to back.

+		if (fillable >= 8 && !(off % 8)) {
+			ret = vfio_pci_core_iordwr64(vdev, iswrite, test_mem,
+						     io, buf, off, &filled);
+			if (ret)
+				return ret;
+		} else
+#endif /* defined(ioread64) && defined(iowrite64) */
  		if (fillable >= 4 && !(off % 4)) {
  			ret = vfio_pci_core_iordwr32(vdev, iswrite, test_mem,
  						     io, buf, off, &filled);
diff --git a/include/linux/vfio_pci_core.h b/include/linux/vfio_pci_core.h
index a2c8b8bba711..f4cf5fd2350c 100644
--- a/include/linux/vfio_pci_core.h
+++ b/include/linux/vfio_pci_core.h
@@ -157,5 +157,8 @@ int vfio_pci_core_ioread##size(struct vfio_pci_core_device *vdev,	\
+#ifdef ioread64
nit: This macro is referenced only in this file. Can the typo be corrected (_DECLARATION)?

#endif /* VFIO_PCI_CORE_H */

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