[libvirt] [PATCH 1/2] virpci: Introduce virPCIDeviceIsPCIExpress and friends

Martin Kletzander mkletzan at redhat.com
Thu Jun 12 08:56:51 UTC 2014


On Fri, Jun 06, 2014 at 12:54:17PM +0200, Michal Privoznik wrote:
>These functions will handle PCIe devices and their link capabilities
>to query some info about it.
>
>Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>---
> src/libvirt_private.syms |  3 ++
> src/util/virpci.c        | 81 +++++++++++++++++++++++++++++++++++++++++++++++-
> src/util/virpci.h        |  8 +++++
> 3 files changed, 91 insertions(+), 1 deletion(-)
>
>diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
>index d73a9f5..f72a3ad 100644
>--- a/src/libvirt_private.syms
>+++ b/src/libvirt_private.syms
>@@ -1690,6 +1690,8 @@ virPCIDeviceFree;
> virPCIDeviceGetDriverPathAndName;
> virPCIDeviceGetIOMMUGroupDev;
> virPCIDeviceGetIOMMUGroupList;
>+virPCIDeviceGetLinkCap;
>+virPCIDeviceGetLinkSta;
> virPCIDeviceGetManaged;
> virPCIDeviceGetName;
> virPCIDeviceGetRemoveSlot;
>@@ -1698,6 +1700,7 @@ virPCIDeviceGetStubDriver;
> virPCIDeviceGetUnbindFromStub;
> virPCIDeviceGetUsedBy;
> virPCIDeviceIsAssignable;
>+virPCIDeviceIsPCIExpress;
> virPCIDeviceListAdd;
> virPCIDeviceListAddCopy;
> virPCIDeviceListCount;
>diff --git a/src/util/virpci.c b/src/util/virpci.c
>index e0f2344..8ad28b8 100644
>--- a/src/util/virpci.c
>+++ b/src/util/virpci.c
>@@ -130,7 +130,13 @@ struct _virPCIDeviceList {
>
> /* PCIe20 7.8.3  Device Capabilities Register (Offset 04h) */
> #define PCI_EXP_DEVCAP          0x4     /* Device capabilities */
>-#define PCI_EXP_DEVCAP_FLR     (1<<28) /* Function Level Reset */
>+#define PCI_EXP_LNKCAP          0xc     /* Link Capabilities */
>+#define PCI_EXP_LNKSTA          0x12    /* Link Status */
>+#define PCI_EXP_DEVCAP_FLR     (1<<28)  /* Function Level Reset */
>+#define PCI_EXP_LNKCAP_SPEED    0x0000f /* Maximum Link Speed */
>+#define PCI_EXP_LNKCAP_WIDTH    0x003f0 /* Maximum Link Width */
>+#define PCI_EXP_LNKSTA_SPEED    0x000f  /* Negotiated Link Speed */
>+#define PCI_EXP_LNKSTA_WIDTH    0x03f0  /* Negotiated Link Width */
>

These two sets are essentially the same, just keep it as e.g.
PCI_EXP_LINK_(SPEED|WIDTH) with 0x(f|3f) respectively.  And keep the
order of the names alphabetical.

> /* Header type 1 BR12 3.2 PCI-to-PCI Bridge Configuration Space Header Format */
> #define PCI_PRIMARY_BUS         0x18    /* BR12 3.2.5.2 Primary bus number */
>@@ -2750,3 +2756,76 @@ virPCIGetVirtualFunctionInfo(const char *vf_sysfs_device_path ATTRIBUTE_UNUSED,
>     return -1;
> }
> #endif /* __linux__ */
>+
>+int
>+virPCIDeviceIsPCIExpress(virPCIDevicePtr dev)
>+{
>+    int fd;
>+    int ret = -1;
>+
>+    if ((fd = virPCIDeviceConfigOpen(dev, true)) < 0)
>+        return ret;
>+
>+    if (virPCIDeviceInit(dev, fd) < 0)
>+        goto cleanup;
>+
>+    ret = dev->pcie_cap_pos != 0;
>+
>+ cleanup:
>+    virPCIDeviceConfigClose(dev, fd);
>+    return ret;
>+}
>+
>+int
>+virPCIDeviceGetLinkCap(virPCIDevicePtr dev,
>+                       int *port,
>+                       unsigned int *speed,
>+                       unsigned int *width)
>+{
>+    uint32_t t;
>+    int fd;
>+    int ret = -1;
>+
>+    if ((fd = virPCIDeviceConfigOpen(dev, true) < 0))
>+        return ret;
>+
>+    if (virPCIDeviceInit(dev, fd) < 0)
>+        goto cleanup;
>+
>+    t = virPCIDeviceRead32(dev, fd, dev->pcie_cap_pos + PCI_EXP_LNKCAP);
>+
>+    *port = t >> 0x18;

Took me second to figure out you just want the highest byte.
s/0x18/24/ would make that much more clear, at least for me.

>+    *speed = t & PCI_EXP_LNKCAP_SPEED;
>+    *width = (t & PCI_EXP_LNKCAP_WIDTH) >> 4;

And if I wanted to be *really* digging deep into this and nitpicking a
lot, I'd say you can do:

port = Read8
speed = Read16 & SPEED
width = Read8

>+    ret = 0;
>+
>+ cleanup:
>+    virPCIDeviceConfigClose(dev, fd);
>+    return ret;
>+}
>+
>+int
>+virPCIDeviceGetLinkSta(virPCIDevicePtr dev,
>+                       unsigned int *speed,
>+                       unsigned int *width)
>+{
>+    uint32_t t;
>+    int fd;
>+    int ret = -1;
>+
>+    if ((fd = virPCIDeviceConfigOpen(dev, true) < 0))
>+        return ret;
>+
>+    if (virPCIDeviceInit(dev, fd) < 0)
>+        goto cleanup;
>+
>+    t = virPCIDeviceRead32(dev, fd, dev->pcie_cap_pos + PCI_EXP_LNKSTA);
>+
>+    *speed = t & PCI_EXP_LNKSTA_SPEED;
>+    *width = (t & PCI_EXP_LNKSTA_WIDTH) >> 4;
>+    ret = 0;
>+
>+ cleanup:
>+    virPCIDeviceConfigClose(dev, fd);
>+    return ret;
>+}

Both these functions do the same thing with 2 micro differences,
either merge it to one, so you avoid double open, init, etc.  Or
create one that at least takes a parameter saying whether the caller
wants CAPability or STAtus data.

Other than that it looks good.

Martin
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