[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [v1 1/2] xen/p2m: Create identity mappings for PFNs beyound E820 and PCI BARs
On Fri, Oct 25, 2013 at 11:03:20AM -0400, Konrad Rzeszutek Wilk wrote: > On bootup the E820 "gaps" or E820_RESV regions are marked as > identity regions. Meaning that any lookup done in the P2M > will return the same value: pfn_to_mfn(pfn) == pfn. > > This is needed for PCI devices so that drivers can reference > the correct bus address. Unfortunatly there are also PCIe > devices which setup their MMIO region above the E820. By default > we assume in the P2M that any region above the last E820 entry > is to be used for ballooning. That is not true - and we don't > mark such regions as IDENTIY_FRAME but INVALID_P2M_ENTRY. > The result is that any lookup in the P2M (pfn_to_mfn(pfn) == 0) > gets us the 0 bus address which is hardly correct. > > A solution that this patch implements is to walk the PCI device > BAR regions and mark them as IDENTITY_FRAMEs in the P2M. > Naturally some checks are needed such as making sure that the > BAR regions are not part of the balloon pages, nor regular RAM. > > We only set them to IDENTITY if the: > pfn_to_mfn(pfn) == INVALID_P2M_ENTRY. > > Another solution would be to mark all P2M entries beyond the > last E820 entry _and_ not in the balloon regions as IDENTITY. > > If done, that means in worst case we have to reserve MAX_DOMAIN_PAGES > pages (so 2MB) of virtual space in case we have to create > new P2M leafs. We could be fancy and make the P2M code understand > p2m_mid_missing and p2_mid_identity and do the right things. > But that is quite complex while this particular patch only > gets invoked if there are PCI devices. Another solution (David > Vrabel ideas) was to consider INVALID_P2M_ENTRY as 1-1 regions. > The author of this patch is not sure of the ramifications > as it would require surgery in various P2M codebits. > > Reported-by: Lukas Hejtmanek <xhejtman@xxxxxxxxxxx> > Reported-by: Lance Larsh <lance.larsh@xxxxxxxxxx> > CC: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx> > CC: David Vrabel <david.vrabel@xxxxxxxxxx> > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> > --- > drivers/xen/balloon.c | 19 +++++++++++++ > drivers/xen/pci.c | 79 > +++++++++++++++++++++++++++++++++++++++++++++++++-- > include/xen/balloon.h | 1 + > 3 files changed, 96 insertions(+), 3 deletions(-) > > diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c > index b232908..258e3f9 100644 > --- a/drivers/xen/balloon.c > +++ b/drivers/xen/balloon.c > @@ -133,6 +133,25 @@ static void balloon_append(struct page *page) > adjust_managed_page_count(page, -1); > } > > +/* > + * Check if any the balloon pages overlap with the supplied > + * pfn and its range. > + */ > +bool balloon_pfn(unsigned long pfn, unsigned long nr) > +{ > + struct page *page; > + > + if (list_empty(&ballooned_pages)) > + return false; > + > + list_for_each_entry(page, &ballooned_pages, lru) { > + unsigned long b_pfn = page_to_pfn(page); > + > + if (b_pfn >= pfn && b_pfn < pfn + nr) > + return true; > + } > + return false; > +} > /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */ > static struct page *balloon_retrieve(bool prefer_highmem) > { > diff --git a/drivers/xen/pci.c b/drivers/xen/pci.c > index 18fff88..6b86eda 100644 > --- a/drivers/xen/pci.c > +++ b/drivers/xen/pci.c > @@ -22,6 +22,9 @@ > #include <xen/xen.h> > #include <xen/interface/physdev.h> > #include <xen/interface/xen.h> > +#include <xen/interface/memory.h> > +#include <xen/page.h> > +#include <xen/balloon.h> > > #include <asm/xen/hypervisor.h> > #include <asm/xen/hypercall.h> > @@ -127,6 +130,72 @@ static int xen_add_device(struct device *dev) > return r; > } > > +static void xen_p2m_add_device(struct device *dev) > +{ > + int i; > + struct pci_dev *pci_dev = to_pci_dev(dev); > + > + /* Verify whether the MMIO BARs are 1-1 in the P2M. */ > + for (i = 0; i < PCI_NUM_RESOURCES; i++) { > + unsigned long pfn, start, end, ok_pfns; > + char bus_addr[64]; > + char *fmt; > + > + if (!pci_resource_len(pci_dev, i)) > + continue; > + > + if (pci_resource_flags(pci_dev, i) == IORESOURCE_IO) > + fmt = " (bus address [%#06llx-%#06llx])"; > + else > + fmt = " (bus address [%#010llx-%#010llx])"; > + > + snprintf(bus_addr, sizeof(bus_addr), fmt, > + (unsigned long long) (pci_resource_start(pci_dev, i)), > + (unsigned long long) (pci_resource_end(pci_dev, i))); > + > + start = pci_resource_start(pci_dev, i) >> PAGE_SHIFT; > + end = pci_resource_end(pci_dev, i) >> PAGE_SHIFT; > + > + /* > + * We don't worry about the balloon scratch page as it has a > + * valid PFN - which means we will catch in the loop below. > + */ > + if (balloon_pfn(start, end - start)) { > + dev_warn(dev, "%s is within balloon pages!\n", > bus_addr); > + continue; > + } > + > + for (ok_pfns = 0, pfn = start; pfn < end; pfn++) { > + unsigned long mfn = pfn_to_mfn(pfn); > + > + if (mfn == pfn) { > + ok_pfns++; > + continue; > + } > + if (mfn != INVALID_P2M_ENTRY) { /* RAM */ > + dev_warn(dev, "%s is within RAM [%lx] > region!\n", bus_addr, pfn); > + break; > + } > + } > + if (ok_pfns == end - start) /* All good. */ > + continue; > + > + if (pfn != end - 1) /* We broke out of the loop above. */ > + continue; There are some bugs in this code so please wait until the next posting which hopefully will also include me testing it on affected hardware. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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