Re: [Qemu-devel] [RFC PATCH]pci-assign: Fix memory out of bound when MSI-X table not fit in a single page

[Gonglei (Arei)]

> > Hi,
> >
> > I have a problem about SR-IOV pass-through.
> >
> > The PF is Emulex Corporation OneConnect NIC (Lancer)(rev 10),
> > and the VF pci config is as follow:
> >
> > LINUX:/sys/bus/pci/devices/0000:04:00.6 # hexdump config
> > 0000000 ffff ffff 0000 0010 0010 0200 0000 0080
> > 0000010 0000 0000 0000 0000 0000 0000 0000 0000
> > 0000020 0000 0000 0000 0000 0000 0000 10df e264
> > 0000030 0000 0000 0054 0000 0000 0000 0000 0000
> > 0000040 0000 0000 0008 0000 0000 0000 0000 0000
> > 0000050 0000 0000 6009 0008 2b41 c002 0000 0000
> > 0000060 7805 018a 0000 0000 0000 0000 0000 0000
> > 0000070 0000 0000 0000 0000 8411 03ff 4000 0000
> > 0000080 3400 0000 9403 0000 0000 0000 0000 0000
> > 0000090 0000 0000 0010 0002 8724 1000 0000 0000
> > 00000a0 dc83 0041 0000 0000 0000 0000 0000 0000
> > 00000b0 0000 0000 0000 0000 001f 0010 0000 0000
> > 00000c0 000e 0000 0000 0000 0000 0000 0000 0000
> > 00000d0 0000 0000 0000 0000 0000 0000 0000 0000
> >
> > We can see the msix_max is 0x3ff and msix_table_entry is 0x4000 (4 pages).
> But QEMU
> > only mmap MSIX_PAGE_SIZE memory for all pci devices in funciton
> assigned_dev_register_msix_mmio,
> > meanwhile the set the one page memmory to zero, so the rest memory will
> be random value
> > (maybe etnry.data is not 0).
> >
> > In function assigned_dev_update_msix_mmio maybe occur the issue of
> entry_nr > 256,
> > and the kmod reports the EINVAL error.
> >
> > My patch fix this issue which alloc memory according to the real size of pci
> device config.
> >
> > Any ideas? Thnaks.
> >
> > Signed-off-by: Gonglei <address@hidden>
> > ---
> >  hw/i386/kvm/pci-assign.c |   24 +++++++++++++++++++-----
> >  1 files changed, 19 insertions(+), 5 deletions(-)
> >
> > diff --git a/hw/i386/kvm/pci-assign.c b/hw/i386/kvm/pci-assign.c
> > index a825871..daa191c 100644
> > --- a/hw/i386/kvm/pci-assign.c
> > +++ b/hw/i386/kvm/pci-assign.c
> > @@ -1591,10 +1591,6 @@ static void
> assigned_dev_msix_reset(AssignedDevice *dev)
> >      MSIXTableEntry *entry;
> >      int i;
> >
> > -    if (!dev->msix_table) {
> > -        return;
> > -    }
> > -
> >      memset(dev->msix_table, 0, MSIX_PAGE_SIZE);
> >
> >      for (i = 0, entry = dev->msix_table; i < dev->msix_max; i++, entry++) {
> > @@ -1604,13 +1600,31 @@ static void
> assigned_dev_msix_reset(AssignedDevice *dev)
> >
> >  static int assigned_dev_register_msix_mmio(AssignedDevice *dev)
> >  {
> > -    dev->msix_table = mmap(NULL, MSIX_PAGE_SIZE,
> PROT_READ|PROT_WRITE,
> > +    int nr_pages;
> > +    int size;
> > +    int entry_per_page = MSIX_PAGE_SIZE / sizeof(struct MSIXTableEntry);
> > +
> > +    if (dev->msix_max > entry_per_page) {
> > +        nr_pages = dev->msix_max / entry_per_page;
> > +        if (dev->msix_max % entry_per_page) {
> > +            nr_pages += 1;
> > +        }
> > +    } else {
> > +        nr_pages = 1;
> > +    }
> 
> It's usually not a good idea to special-case corner-cases like this.
> 
IMHO, we should assure the memory page-aligned, so I use ROUND_UP according to 
dev->msix_max.

> 
> > +
> > +    size = MSIX_PAGE_SIZE * nr_pages;
> 
> Just use ROUND_UP?
> 
> > +    dev->msix_table = mmap(NULL, size, PROT_READ|PROT_WRITE,
> >                             MAP_ANONYMOUS|MAP_PRIVATE, 0, 0);
> 
> Need to fix unmap as well?
> 
Yep, it should be unmap for new size memory in 
assigned_dev_unregister_msix_mmio. Thanks, Michael.

BTW, do you think the KVM should upsize the max support MSI-X entry to 2048.
Because the MSI-X supports a maximum table size of 2048 entries, which is 
descript in 
PCI specification 3.0 version 6.8.3.2: "MSI-X Configuration".

The history patch about downsize the MSI-X entry size to 256:
http://thread.gmane.org/gmane.comp.emulators.kvm.devel/38852/focus=38849

Best regards,
-Gonglei