Rather than always binding to the vfio-pci driver, use the new
function virPCIDeviceFindBestVFIOVariant() to see if the running
kernel has a VFIO variant driver available that is a better match for
the device, and if one is found, use that instead.
virPCIDeviceFindBestVFIOVariant() function reads the modalias file for
the given device from sysfs, then looks through
/lib/modules/${kernel_release}/modules.alias for the vfio_pci alias
that matches with the least number of wildcard ('*') fields.
The appropriate "VFIO variant" driver for a device will be the PCI
driver implemented by the discovered module - these drivers are
compatible with (and provide the entire API of) the standard vfio-pci
driver, but have additional device-specific APIs that can be useful
for, e.g., saving/restoring state for migration.
If a specific driver is named (using <driver model='blah'/> in the
device XML), that will still be used rather than searching
modules.alias; this makes it possible to force binding of vfio-pci if
there is an issue with the auto-selected variant driver.
Signed-off-by: Laine Stump <laine@xxxxxxxxxx>
---
Changes from V2:
* fail if device modalias file isn't found.
* use unsigned int instead of int for wildcardCt
* increase file memory buffer from 4MB to 8MB
* other minor nits pointed out by Peter
src/libvirt_private.syms | 1 +
src/util/virpci.c | 219 +++++++++++++++++++++++++++++++++++++++
src/util/virpci.h | 2 +
tests/virpcimock.c | 9 ++
4 files changed, 231 insertions(+)
diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index cccefe5a81..2cf01c5f50 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -3076,6 +3076,7 @@ virPCIDeviceCopy;
virPCIDeviceDetach;
virPCIDeviceExists;
virPCIDeviceFileIterate;
+virPCIDeviceFindBestVFIOVariant;
virPCIDeviceFree;
virPCIDeviceGetAddress;
virPCIDeviceGetConfigPath;
diff --git a/src/util/virpci.c b/src/util/virpci.c
index f6bdf56057..99d6740ed1 100644
--- a/src/util/virpci.c
+++ b/src/util/virpci.c
@@ -30,6 +30,10 @@
#include <sys/stat.h>
#include <unistd.h>
+#ifdef __linux__
+# include <sys/utsname.h>
+#endif
+
#include "virlog.h"
#include "virerror.h"
#include "virfile.h"
@@ -1321,6 +1325,206 @@ virPCIDeviceFindDriver(virPCIDevice *dev)
}
+#ifdef __linux__
+typedef struct {
+ /* this is the decomposed version of a string like:
+ *
+ * vNNNNNNNNdNNNNNNNNsvNNNNNNNNsdNNNNNNNNbcNNscNNiNN
+ *
+ * (followed by a space or newline). The "NNNN" are always of the
+ * length in the example unless replaced with a wildcard ("*"),
+ * but we make no assumptions about length.
+ *
+ * Rather than name each field, we just put them
+ * all in an array of 7 elements, so that we
+ * can write a simple loop to compare them
+ */
+ char *fields[7]; /* v, d, sv, sd, bc, sc, i */
+} virPCIDeviceAliasInfo;
+
+
+/* NULL in last position makes parsing loop simpler */
+static const char *fieldnames[] = { "v", "d", "sv", "sd", "bc", "sc", "i", NULL };
+
+
+static void
+virPCIDeviceAliasInfoFree(virPCIDeviceAliasInfo *info)
+{
+ if (info) {
+ size_t i;
+
+ for (i = 0; i < G_N_ELEMENTS(info->fields); i++)
+ g_free(info->fields[i]);
+
+ g_free(info);
+ }
+}
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(virPCIDeviceAliasInfo, virPCIDeviceAliasInfoFree);
+
+
+static virPCIDeviceAliasInfo *
+virPCIDeviceAliasInfoNew(const char *str)
+{
+ const char *field = str;
+
+ size_t i;
+ g_autoptr(virPCIDeviceAliasInfo) ret = g_new0(virPCIDeviceAliasInfo, 1);
+
+ /* initialize from str */
+ for (i = 0; i < G_N_ELEMENTS(ret->fields); i++) {
+ int len = strlen(fieldnames[i]);
+ const char *next;
+
+ if (strncmp(field, fieldnames[i], len))
+ return NULL;
+
+ field += len;
+ if (fieldnames[i + 1]) {
+ if (!(next = strstr(field, fieldnames[i + 1])))
+ return NULL;
+ } else {
+ next = field;
+ while (*next && !g_ascii_isspace(*next))
+ next++;
+ }
+
+ ret->fields[i] = g_strndup(field, next - field);
+ field = next;
+ }
+
+ return g_steal_pointer(&ret);
+}
+
+
+static bool
+virPCIDeviceAliasInfoMatch(virPCIDeviceAliasInfo *orig,
+ virPCIDeviceAliasInfo *match,
+ unsigned int *wildCardCt)
+{
+ size_t i;
+
+ *wildCardCt = 0;
+
+ for (i = 0; i < G_N_ELEMENTS(orig->fields); i++) {
+ if (STREQ(match->fields[i], "*"))
+ (*wildCardCt)++;
+ else if (STRNEQ(orig->fields[i], match->fields[i]))
+ return false;
+ }
+ return true;
+}
+
+
+/* virPCIDeviceFindBestVFIOVariant:
+ *
+ * Find the "best" match of all vfio_pci aliases for @dev in the host
+ * modules.alias file. This uses the algorithm of finding every
+ * modules.alias line that begins with "vfio_pci:", then picking the
+ * one that matches the device's own modalias value (from the file of
+ * that name in the device's sysfs directory) with the fewest
+ * "wildcards" (* character, meaning "match any value for this
+ * attribute").
+ */
+int
+virPCIDeviceFindBestVFIOVariant(virPCIDevice *dev,
+ char **moduleName)
+{
+ g_autofree char *devModAliasPath = NULL;
+ g_autofree char *devModAliasContent = NULL;
+ const char *devModAlias;
+ g_autoptr(virPCIDeviceAliasInfo) devModAliasInfo = NULL;
+ struct utsname unameInfo;
+ g_autofree char *modulesAliasPath = NULL;
+ g_autofree char *modulesAliasContent = NULL;
+ const char *line;
+ unsigned int currentBestWildcardCt = INT_MAX;
+
+ *moduleName = NULL;
+
+ /* get the modalias values for the device from sysfs */
+ devModAliasPath = virPCIFile(dev->name, "modalias");
+ if (virFileReadAll(devModAliasPath, 100, &devModAliasContent) < 0)
+ return -1;
+
+ VIR_DEBUG("modalias path: '%s' contents: '%s'",
+ devModAliasPath, devModAliasContent);
+
+ /* "pci:vNNNNNNNNdNNNNNNNNsvNNNNNNNNsdNNNNNNNNbcNNscNNiNN\n" */
+ if ((devModAlias = STRSKIP(devModAliasContent, "pci:")) == NULL ||
+ !(devModAliasInfo = virPCIDeviceAliasInfoNew(devModAlias))) {
+ virReportError(VIR_ERR_INTERNAL_ERROR,
+ _("device modalias file %1$s content has improper format"),
+ devModAliasPath);
+ return -1;
+ }
+
+ uname(&unameInfo);
+ modulesAliasPath = g_strdup_printf("/lib/modules/%s/modules.alias", unameInfo.release);
+ if (virFileReadAll(modulesAliasPath, 8 * 1024 * 1024, &modulesAliasContent) < 0)
+ return -1;
+
+ /* Look for all lines that are aliases for vfio_pci drivers.
+ * (The first line is always a comment, so we can be sure "alias"
+ * is preceded by a newline)
+ */
+ line = modulesAliasContent;
+
+ while ((line = strstr(line, "\nalias vfio_pci:"))) {
+ g_autoptr(virPCIDeviceAliasInfo) fileModAliasInfo = NULL;
+ unsigned int wildCardCt;
+
+ /* "alias vfio_pci:vNNNNNNNNdNNNNNNNNsvNNNNNNNNsdNNNNNNNNbcNNscNNiNN XXXX\n" */
+ line += strlen("\nalias vfio_pci:");
+ if (!(fileModAliasInfo = virPCIDeviceAliasInfoNew(line)))
+ continue;
+
+ if (virPCIDeviceAliasInfoMatch(devModAliasInfo,
+ fileModAliasInfo, &wildCardCt)) {
+
+ const char *aliasStart = strchr(line, ' ');
+ const char *aliasEnd = NULL;
+ g_autofree char *aliasName = NULL;
+
+ if (!aliasStart) {
+ VIR_WARN("malformed modules.alias vfio_pci: line");
+ continue;
+ }
+
+ aliasStart++;
+ line = aliasEnd = strchrnul(aliasStart, '\n');
+ aliasName = g_strndup(aliasStart, aliasEnd - aliasStart);
+
+ VIR_DEBUG("matching alias '%s' found, %u wildcards, best previously was %u",
+ aliasName, wildCardCt, currentBestWildcardCt);
+
+ if (wildCardCt < currentBestWildcardCt) {
+
+ /* this is a better match than previous */
+ currentBestWildcardCt = wildCardCt;
+ g_free(*moduleName);
+ *moduleName = g_steal_pointer(&aliasName);
+ }
+ }
+ }
+ return 0;
+}
+
+
+#else /* __linux__ */
+
+
+int
+virPCIDeviceFindBestVFIOVariant(virPCIDevice *dev G_GNUC_UNUSED,
+ char **moduleName G_GNUC_UNUSED)
+{
+ virReportSystemError(ENOSYS, "%s",
+ _("VFIO device assignment is not available on this platform"));
+ return -1;
+}
+#endif /* __linux__ */
+
+
int
virPCIDeviceUnbind(virPCIDevice *dev)
{
@@ -1431,6 +1635,21 @@ virPCIDeviceBindToStub(virPCIDevice *dev)
return -1;
}
+ if (dev->stubDriverType == VIR_PCI_STUB_DRIVER_VFIO && !dev->stubDriverName) {
+ g_autofree char *autodetectModuleName = NULL;
+
+ /* automatically use a VFIO variant driver if available for
+ * this device.
+ */
+
+ if (virPCIDeviceFindBestVFIOVariant(dev, &autodetectModuleName) < 0)
+ return -1;
+
+ g_free(dev->stubDriverName);
+ dev->stubDriverName = g_steal_pointer(&autodetectModuleName);
+ }
+
+ /* if a driver name hasn't been decided by now, use default for this type */
if (!dev->stubDriverName) {
const char *stubDriverName = NULL;
diff --git a/src/util/virpci.h b/src/util/virpci.h
index bc7cb2329f..a5bfe9c35d 100644
--- a/src/util/virpci.h
+++ b/src/util/virpci.h
@@ -124,6 +124,8 @@ int virPCIDeviceReset(virPCIDevice *dev,
virPCIDeviceList *activeDevs,
virPCIDeviceList *inactiveDevs);
+int virPCIDeviceFindBestVFIOVariant(virPCIDevice *dev, char **moduleName) G_NO_INLINE;
+
void virPCIDeviceSetManaged(virPCIDevice *dev,
bool managed);
bool virPCIDeviceGetManaged(virPCIDevice *dev);
diff --git a/tests/virpcimock.c b/tests/virpcimock.c
index b2111794e6..13b37bb23d 100644
--- a/tests/virpcimock.c
+++ b/tests/virpcimock.c
@@ -25,6 +25,7 @@
#if defined(__linux__) || defined(__FreeBSD__) || defined(__APPLE__)
# define VIR_MOCK_LOOKUP_MAIN
# include "virmock.h"
+# include "virpci.h"
# include <unistd.h>
# include <fcntl.h>
# include <sys/stat.h>
@@ -925,6 +926,14 @@ pci_driver_handle_unbind(const char *path)
}
+
+int
+virPCIDeviceFindBestVFIOVariant(virPCIDevice *dev G_GNUC_UNUSED,
+ char **moduleName G_GNUC_UNUSED)
+{
+ return 0;
+}
+
/*
* Functions to load the symbols and init the environment
*/
--
2.43.0
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