From 5d2ff7718d35f15636e231219d50d84fbd73ffb5 Mon Sep 17 00:00:00 2001
From: Pali Rohár <pali@kernel.org>
Date: Sat, 5 Nov 2022 17:32:38 +0100
Subject: libpci: mmio-ports: Bypass CPU cache and add barriers for read/write

Between accessing address address and data I/O ports it is needed to issue
barriers. Use explicit readl() for barrier and O_DSYNC to bypass CPU cache.
---
 lib/mmio-ports.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/lib/mmio-ports.c b/lib/mmio-ports.c
index b9e3926..50cbee7 100644
--- a/lib/mmio-ports.c
+++ b/lib/mmio-ports.c
@@ -269,7 +269,7 @@ conf1_init(struct pci_access *a)
   if (!validate_addrs(addrs))
     a->error("Option mmio-conf1.addrs has invalid address format \"%s\".", addrs);
 
-  a->fd = open(devmem, O_RDWR);
+  a->fd = open(devmem, O_RDWR | O_DSYNC); /* O_DSYNC bypass CPU cache for mmap() on Linux */
   if (a->fd < 0)
     a->error("Cannot open %s: %s.", devmem, strerror(errno));
 }
@@ -316,6 +316,7 @@ conf1_read(struct pci_dev *d, int pos, byte *buf, int len)
     return 0;
 
   writel(0x80000000 | ((d->bus & 0xff) << 16) | (PCI_DEVFN(d->dev, d->func) << 8) | (pos & 0xfc), addr);
+  readl(addr); /* write barrier for address */
 
   switch (len)
     {
@@ -353,6 +354,7 @@ conf1_write(struct pci_dev *d, int pos, byte *buf, int len)
     return 0;
 
   writel(0x80000000 | ((d->bus & 0xff) << 16) | (PCI_DEVFN(d->dev, d->func) << 8) | (pos & 0xfc), addr);
+  readl(addr); /* write barrier for address */
 
   switch (len)
     {
@@ -367,6 +369,17 @@ conf1_write(struct pci_dev *d, int pos, byte *buf, int len)
       break;
     }
 
+  /*
+   * write barrier for data
+   * Note that we cannot read from data port because it may have side effect.
+   * Instead we read from address port (which should not have side effect) to
+   * create a barrier between two conf1_write() calls. But this does not have
+   * to be 100% correct as it does not ensure barrier on data port itself.
+   * Correct way is to issue CPU instruction for full hw sync barrier but gcc
+   * does not provide any (builtin) function yet.
+   */
+  readl(addr);
+
   return 1;
 }
 
-- 
cgit 1.2.3-korg


From 438cde95675a2d9f2848962848c0f109423bed1f Mon Sep 17 00:00:00 2001
From: Pali Rohár <pali@kernel.org>
Date: Sat, 5 Nov 2022 17:36:42 +0100
Subject: libpci: mmio-ports: Add configure note messages

---
 lib/configure | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/configure b/lib/configure
index 978b21c..7676c0b 100755
--- a/lib/configure
+++ b/lib/configure
@@ -97,7 +97,7 @@ case $sys in
 		echo >>$c '#define PCI_HAVE_STDINT_H'
 		;;
 	freebsd*|kfreebsd*)
-		echo_n " fbsd-device"
+		echo_n " fbsd-device mem-ports"
 		echo >>$c '#define PCI_HAVE_PM_FBSD_DEVICE'
 		echo >>$c '#define PCI_HAVE_PM_MMIO_CONF'
 		echo >>$c '#define PCI_PATH_FBSD_DEVICE "/dev/pci"'
@@ -107,7 +107,7 @@ case $sys in
 		fi
 		;;
         openbsd)
-	        echo_n " obsd-device"
+	        echo_n " obsd-device mem-ports"
 		echo >>$c '#define PCI_HAVE_PM_OBSD_DEVICE'
 		echo >>$c '#define PCI_HAVE_PM_MMIO_CONF'
 		echo >>$c '#define PCI_PATH_OBSD_DEVICE "/dev/pci"'
@@ -136,7 +136,7 @@ case $sys in
 		echo >>$m 'DIRINSTALL=mkdir -p'
 		;;
 	netbsd)
-		echo_n " nbsd-libpci"
+		echo_n " nbsd-libpci mem-ports"
 		echo >>$c '#define PCI_HAVE_PM_NBSD_LIBPCI'
 		echo >>$c '#define PCI_HAVE_PM_MMIO_CONF'
 		echo >>$c '#define PCI_PATH_NBSD_DEVICE "/dev/pci0"'
-- 
cgit 1.2.3-korg


From b0c61ad624f8398b91bcdd201cdf13dc02d51372 Mon Sep 17 00:00:00 2001
From: Pali Rohár <pali@kernel.org>
Date: Sat, 5 Nov 2022 17:51:25 +0100
Subject: libpci: mmio-ports: Check for write access to /dev/mem in detect
 method

---
 lib/mmio-ports.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/mmio-ports.c b/lib/mmio-ports.c
index 50cbee7..ae9c30d 100644
--- a/lib/mmio-ports.c
+++ b/lib/mmio-ports.c
@@ -243,9 +243,9 @@ conf1_detect(struct pci_access *a)
       return 0;
     }
 
-  if (access(devmem, R_OK))
+  if (access(devmem, R_OK | W_OK))
     {
-      a->debug("cannot access %s", devmem);
+      a->debug("cannot access %s: %s", devmem, strerror(errno));
       return 0;
     }
 
-- 
cgit 1.2.3-korg