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Date:      Wed, 4 Mar 2009 21:04:52 +0000 (UTC)
From:      John Baldwin <jhb@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r189373 - head/sys/dev/pci
Message-ID:  <200903042104.n24L4qMc053293@svn.freebsd.org>
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Author: jhb
Date: Wed Mar  4 21:04:52 2009
New Revision: 189373
URL: http://svn.freebsd.org/changeset/base/189373

Log:
  The recent PCI resource allocation fixes exposed a bug where the same
  BAR could be allocated twice by different children of a vgapci0 device.
  To fix this, change the vgapci0 device to track references on its associated
  resources so that they are only allocated once from the parent PCI bus and
  released when no children are using them.  Previously this leaked a small
  amount of KVA on at least some architectures.

Modified:
  head/sys/dev/pci/vga_pci.c

Modified: head/sys/dev/pci/vga_pci.c
==============================================================================
--- head/sys/dev/pci/vga_pci.c	Wed Mar  4 20:58:22 2009	(r189372)
+++ head/sys/dev/pci/vga_pci.c	Wed Mar  4 21:04:52 2009	(r189373)
@@ -42,12 +42,20 @@ __FBSDID("$FreeBSD$");
 #include <sys/bus.h>
 #include <sys/kernel.h>
 #include <sys/module.h>
+#include <sys/rman.h>
+#include <sys/systm.h>
 
 #include <dev/pci/pcireg.h>
 #include <dev/pci/pcivar.h>
 
+struct vga_resource {
+	struct resource	*vr_res;
+	int	vr_refs;
+};
+
 struct vga_pci_softc {
 	device_t	vga_msi_child;	/* Child driver using MSI. */
+	struct vga_resource vga_res[PCIR_MAX_BAR_0 + 1];
 };
 
 static int
@@ -130,7 +138,27 @@ static struct resource *
 vga_pci_alloc_resource(device_t dev, device_t child, int type, int *rid,
     u_long start, u_long end, u_long count, u_int flags)
 {
+	struct vga_pci_softc *sc;
+	int bar;
 
+	switch (type) {
+	case SYS_RES_MEMORY:
+	case SYS_RES_IOPORT:
+		/*
+		 * For BARs, we cache the resource so that we only allocate it
+		 * from the PCI bus once.
+		 */
+		bar = PCI_RID2BAR(*rid);
+		if (bar < 0 || bar > PCIR_MAX_BAR_0)
+			return (NULL);
+		sc = device_get_softc(dev);
+		if (sc->vga_res[bar].vr_res == NULL)
+			sc->vga_res[bar].vr_res = bus_alloc_resource(dev, type,
+			    rid, start, end, count, flags);
+		if (sc->vga_res[bar].vr_res != NULL)
+			sc->vga_res[bar].vr_refs++;
+		return (sc->vga_res[bar].vr_res);
+	}
 	return (bus_alloc_resource(dev, type, rid, start, end, count, flags));
 }
 
@@ -138,6 +166,37 @@ static int
 vga_pci_release_resource(device_t dev, device_t child, int type, int rid,
     struct resource *r)
 {
+	struct vga_pci_softc *sc;
+	int bar, error;
+
+	switch (type) {
+	case SYS_RES_MEMORY:
+	case SYS_RES_IOPORT:
+		/*
+		 * For BARs, we release the resource from the PCI bus
+		 * when the last child reference goes away.
+		 */
+		bar = PCI_RID2BAR(rid);
+		if (bar < 0 || bar > PCIR_MAX_BAR_0)
+			return (EINVAL);
+		sc = device_get_softc(dev);
+		if (sc->vga_res[bar].vr_res == NULL)
+			return (EINVAL);
+		KASSERT(sc->vga_res[bar].vr_res == r,
+		    ("vga_pci resource mismatch"));
+		if (sc->vga_res[bar].vr_refs > 1) {
+			sc->vga_res[bar].vr_refs--;
+			return (0);
+		}
+		KASSERT(sc->vga_res[bar].vr_refs > 0,
+		    ("vga_pci resource reference count underflow"));
+		error = bus_release_resource(dev, type, rid, r);
+		if (error == 0) {
+			sc->vga_res[bar].vr_res = NULL;
+			sc->vga_res[bar].vr_refs = 0;
+		}
+		return (error);
+	}
 
 	return (bus_release_resource(dev, type, rid, r));
 }

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