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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Re: [PATCH 6 of 6] xl: implement multifunction device PCI pass-through
On Wed, 2010-08-04 at 16:47 +0100, Stefano Stabellini wrote:
> On Wed, 4 Aug 2010, Gianni Tedesco (3P) wrote:
> > On Wed, 2010-08-04 at 15:52 +0100, Stefano Stabellini wrote:
> > > On Mon, 2 Aug 2010, Gianni Tedesco (3P) wrote:
> > > > tools/libxl/libxl.h | 1 +
> > > > tools/libxl/libxl_pci.c | 118
> > > > ++++++++++++++++++++++++++++++++++++++++++++---
> > > > 2 files changed, 111 insertions(+), 8 deletions(-)
> > > >
> > > >
> > > > # HG changeset patch
> > > > # User Gianni Tedesco <gianni.tedesco@xxxxxxxxxx>
> > > > # Date 1280760698 -3600
> > > > # Branch pci-patches-v3
> > > > # Node ID 6379343447e58cc7b83e27beba9c35e62c232d9d
> > > > # Parent eb8ee481bc063b18b39feaa76d9b757331ed3a9f
> > > > xl: implement multifunction device PCI pass-through
> > > >
> > > > Implement PCI pass-through for multi-function devices. The supported BDF
> > > > notation is: BB:DD.* - therefore passing-through a subset of functions
> > > > or
> > > > remapping the function numbers is not supported. Largely because I
> > > > don't see
> > > > how that can ever be safe or sane (perhaps for SR-IOV cards?)
> > > >
> > > > Letting qemu automatically select the virtual slot is not supported
> > > > since I
> > > > don't believe that qemu-dm can actually handle that case.
> > > >
> > > > Signed-off-by: Gianni Tedesco <gianni.tedesco@xxxxxxxxxx>
> > > >
> > > > diff -r eb8ee481bc06 -r 6379343447e5 tools/libxl/libxl.h
> > > > --- a/tools/libxl/libxl.h Mon Aug 02 15:47:38 2010 +0100
> > > > +++ b/tools/libxl/libxl.h Mon Aug 02 15:51:38 2010 +0100
> > > > @@ -308,6 +308,7 @@ typedef struct {
> > > > unsigned int vdevfn;
> > > > bool msitranslate;
> > > > bool power_mgmt;
> > > > + bool multifunction;
> > > > } libxl_device_pci;
> > > >
> > > > enum {
> > > > diff -r eb8ee481bc06 -r 6379343447e5 tools/libxl/libxl_pci.c
> > > > --- a/tools/libxl/libxl_pci.c Mon Aug 02 15:47:38 2010 +0100
> > > > +++ b/tools/libxl/libxl_pci.c Mon Aug 02 15:51:38 2010 +0100
> > > > @@ -136,8 +136,13 @@ int libxl_device_pci_parse_bdf(libxl_ctx
> > > > break;
> > > > }
> > > > *ptr = '\0';
> > > > - if ( hex_convert(tok, &func, 0x7) )
> > > > - goto parse_error;
> > > > + if ( !strcmp(tok, "*") ) {
> > > > + pcidev->multifunction = 1;
> > > > + }else{
> > > > + if ( hex_convert(tok, &func, 0x7) )
> > > > + goto parse_error;
> > > > + pcidev->multifunction = 0;
> > > > + }
> > > > tok = ptr + 1;
> > > > }
> > > > break;
> > >
> > > Couldn't you add the func_mask somewhere in libxl_device_pci, instead of
> > > calling pci_multifunction_check multilple times?
> > > Would be possible to make the normal passthrough case just a subset of
> > > the general multifunction passthrough case to simplify the code?
> >
> > Not sure what you mean by this, the parsing parts don't (and oughtn't)
> > frob about with sysfs nodes etc. The pci_multifunction_check function is
> > called once per device add and once per device remove iff the parser had
> > seen XX:YY.* notation indicating multifunction devices.
> >
>
> I mean we could have a mask instead of an interger in libxl_device_pci
> to specify which functions should be assigned and in the single function
> case the mask will have only one bit set.
> At this point single function passthrough become just a case of
> multifunction passthrough.
> I am not entirely sure that this approach would produce better code
> though.
I see what you mean. I could set it to #define PCI_FUNCTION_EVERYTHING
~0 at parse-time then in multifunction_check unset all the non-existent
functions.
>
> > >
> > > > @@ -531,6 +536,50 @@ int libxl_device_pci_list_assignable(lib
> > > > return 0;
> > > > }
> > > >
> > > > +static int pci_multifunction_check(libxl_ctx *ctx, libxl_device_pci
> > > > *pcidev, unsigned int *func_mask)
> > > > +{
> > >
> > > a comment on top of this function to explain what it is actually checking
> > > would be nice
> >
> > This function checks that all functions of a device are bound to pciback
> > driver. It also initialises a bit-mask of which function numbers are
> > present on that device.
> >
> > I shall add the comment in next rev.
> >
> > > > + struct dirent *de;
> > > > + DIR *dir;
> > > > +
> > > > + *func_mask = 0;
> > > > +
> > > > + dir = opendir(SYSFS_PCI_DEV);
> > > > + if ( NULL == dir ) {
> > > > + XL_LOG_ERRNO(ctx, XL_LOG_ERROR, "Couldn't open %s",
> > > > SYSFS_PCI_DEV);
> > > > + return -1;
> > > > + }
> > > > +
> > > > + while( (de = readdir(dir)) ) {
> > > > + unsigned dom, bus, dev, func;
> > > > + struct stat st;
> > > > + char *path;
> > > > +
> > > > + if ( sscanf(de->d_name, PCI_BDF, &dom, &bus, &dev, &func) != 4
> > > > )
> > > > + continue;
> > > > + if ( pcidev->domain != dom )
> > > > + continue;
> > > > + if ( pcidev->bus != bus )
> > > > + continue;
> > > > + if ( pcidev->dev != dev )
> > > > + continue;
> > > > +
> > > > + path = libxl_sprintf(ctx, "%s/" PCI_BDF, SYSFS_PCIBACK_DRIVER,
> > > > dom, bus, dev, func);
> > > > + if ( lstat(path, &st) ) {
> > > > + if ( errno == ENOENT )
> > > > + XL_LOG(ctx, XL_LOG_ERROR, PCI_BDF " is not assigned to
> > > > pciback driver",
> > > > + dom, bus, dev, func);
> > > > + else
> > > > + XL_LOG_ERRNO(ctx, XL_LOG_ERROR, "Couldn't lstat %s",
> > > > path);
> > > > + closedir(dir);
> > > > + return -1;
> > > > + }
> > > > + (*func_mask) |= (1 << func);
> > > > + }
> > > > +
> > > > + closedir(dir);
> > > > + return 0;
> > > > +}
> > > > +
> > > > static int pci_ins_check(libxl_ctx *ctx, uint32_t domid, const char
> > > > *state, void *priv)
> > > > {
> > > > char *orig_state = priv;
> > > > @@ -679,10 +728,32 @@ int libxl_device_pci_add(libxl_ctx *ctx,
> > > > return rc;
> > > > }
> > > >
> > > > + if ( pcidev->multifunction ) {
> > > > + unsigned int i, orig_vdev, func_mask, rc = 0;
> > > > + orig_vdev = pcidev->vdevfn & ~7U;
> > > > +
> > > > + if ( pci_multifunction_check(ctx, pcidev, &func_mask) )
> > > > + return ERROR_FAIL;
> > > > + if ( !(pcidev->vdevfn >> 3) ) {
> > > > + XL_LOG(ctx, XL_LOG_ERROR, "Must specify a v-slot for
> > > > multi-function devices");
> > > > + return ERROR_FAIL;
> > > > + }
> > > > +
> > > > + for(i = 7; i < 8; --i) {
> > >
> > > shouldn't this be for(i = 7; i >= 0; --i)?
> >
> > That will generate a compiler warning since unsigned int's are always >=
> > 0. The code relies on an underflow condition. However, I could change it
> > to int if you think that makes it clearer.
> >
>
> yeah please do that
OK
> > > > + if ( (1 << i) & func_mask ) {
> > > > + pcidev->func = i;
> > > > + pcidev->vdevfn = orig_vdev | i;
> > > > + if ( do_pci_add(ctx, domid, pcidev) )
> > > > + rc = ERROR_FAIL;
> > > > + }
> > > > + }
> > > > + return rc;
> > > > + }
> > > > +
> > > > return do_pci_add(ctx, domid, pcidev);
> > > > }
> > > >
> > > > -int libxl_device_pci_remove(libxl_ctx *ctx, uint32_t domid,
> > > > libxl_device_pci *pcidev)
> > > > +static int do_pci_remove(libxl_ctx *ctx, uint32_t domid,
> > > > libxl_device_pci *pcidev)
> > > > {
> > > > libxl_device_pci *assigned;
> > > > char *path;
> > > > @@ -711,10 +782,15 @@ int libxl_device_pci_remove(libxl_ctx *c
> > > > libxl_xs_write(ctx, XBT_NULL, path, PCI_BDF, pcidev->domain,
> > > > pcidev->bus, pcidev->dev, pcidev->func);
> > > > path = libxl_sprintf(ctx,
> > > > "/local/domain/0/device-model/%d/command", domid);
> > > > - xs_write(ctx->xsh, XBT_NULL, path, "pci-rem",
> > > > strlen("pci-rem"));
> > > > - if (libxl_wait_for_device_model(ctx, domid, "pci-removed",
> > > > NULL, NULL) < 0) {
> > > > - XL_LOG(ctx, XL_LOG_ERROR, "Device Model didn't respond in
> > > > time");
> > > > - return ERROR_FAIL;
> > > > +
> > > > + /* Remove all functions at once atomically by only signalling
> > > > + * device-model for function 0 */
> > > > + if ( !pcidev->multifunction || pcidev->func == 0 ) {
> > > > + xs_write(ctx->xsh, XBT_NULL, path, "pci-rem",
> > > > strlen("pci-rem"));
> > > > + if (libxl_wait_for_device_model(ctx, domid, "pci-removed",
> > > > NULL, NULL) < 0) {
> > > > + XL_LOG(ctx, XL_LOG_ERROR, "Device Model didn't respond
> > > > in time");
> > > > + return ERROR_FAIL;
> > > > + }
> > > > }
> > > > path = libxl_sprintf(ctx,
> > > > "/local/domain/0/device-model/%d/state", domid);
> > > > xs_write(ctx->xsh, XBT_NULL, path, state, strlen(state));
> > > > @@ -769,7 +845,10 @@ skip1:
> > > > fclose(f);
> > > > }
> > > > out:
> > > > - libxl_device_pci_reset(ctx, pcidev->domain, pcidev->bus,
> > > > pcidev->dev, pcidev->func);
> > > > + /* don't do multiple resets while some functions are still passed
> > > > through */
> > > > + if ( !pcidev->multifunction || pcidev->func == 0 ) {
> > > > + libxl_device_pci_reset(ctx, pcidev->domain, pcidev->bus,
> > > > pcidev->dev, pcidev->func);
> > > > + }
> > > >
> > > > if (!libxl_is_stubdom(ctx, domid, NULL)) {
> > > > rc = xc_deassign_device(ctx->xch, domid, pcidev->value);
> > > > @@ -786,6 +865,29 @@ out:
> > > > return 0;
> > > > }
> > > >
> > > > +int libxl_device_pci_remove(libxl_ctx *ctx, uint32_t domid,
> > > > libxl_device_pci *pcidev)
> > > > +{
> > > > + if ( pcidev->multifunction ) {
> > > > + unsigned int i, orig_vdev, func_mask, rc;
> > > > + orig_vdev = pcidev->vdevfn & ~7U;
> > > > +
> > > > + if ( pci_multifunction_check(ctx, pcidev, &func_mask) )
> > > > + return ERROR_FAIL;
> > > > +
> > > > + for(i = 7; i < 8; --i) {
> > >
> > > same here
> > >
> > > > + if ( (1 << i) & func_mask ) {
> > > > + pcidev->func = i;
> > > > + pcidev->vdevfn = orig_vdev | i;
> > > > + if ( do_pci_remove(ctx, domid, pcidev) )
> > > > + rc = ERROR_FAIL;
> > > > + }
> > > > + }
> > > > + return rc;
> > > > + }
> > > > +
> > > > + return do_pci_remove(ctx, domid, pcidev);
> > > > +}
> > > > +
> > > > int libxl_device_pci_list_assigned(libxl_ctx *ctx, libxl_device_pci
> > > > **list, uint32_t domid, int *num)
> > > > {
> > > > char *be_path, *num_devs, *xsdev, *xsvdevfn, *xsopts;
> > > >
> > >
> > >
> > > applied all the other patches in the series
> >
> > OK thanks.
> >
> > I will also need to handle cleanup in the error path of multifunction
> > device addition as discussed. This can actually happen quite easily if
> > function 0 alone is assigned to another domain because
> > pci_multifunction_check() doesn't look in xenstore and also because of
> > missing safety checks. Specifically, when adding a non-multifunction
> > device we need a check to make sure that the physical device really has
> > only one function.
> >
> > I am thinking that we probably ought to scrap the XX:YY.* notation and
> > enforce that function is ALWAYS set to 0. Then when adding/removing the
> > device we should check for additional functions and handle them
> > transparently to the user. As I said in the commit message I am unaware
> > of any valid uses for separating functions but I need to look at how
> > SR-IOV works.
> >
> >
>
> With SR-IOV devices you can easily have valid BDFs like 0000:05:1c.2, so
> enforcing that function is always 0 is not a good idea.
I will have to look in to that and try come up something that is safe in
all such cases. For now I will just re-work the patch along the lines
you mentioned.
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