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    Subject[RFC v5 4/7] PCI: Add support for enforcing all MMIO BARs to be page aligned
    Date
    When vfio passthrough a PCI device of which MMIO
    BARs are smaller than PAGE_SIZE, guest will not
    handle the mmio accesses to the BARs which leads
    to mmio emulations in host.

    This is because vfio will not allow to passthrough
    one BAR's mmio page which may be shared with other
    BARs. Otherwise, there will be a backdoor that
    guest can use to access BARs of other guest.

    To solve this issue, this patch modifies
    resource_alignment to support syntax where
    multiple devices get the same alignment. So we
    can use something like
    "pci=resource_alignment=*:*:*.*:noresize" to
    enforce the alignment of all MMIO BARs to be at
    least PAGE_SIZE so that one BAR's mmio page would
    not be shared with other BARs.

    And we also define a macro PCIBIOS_MIN_ALIGNMENT
    to enable this automatically on PPC64 platform
    which can easily hit this issue because its
    PAGE_SIZE is 64KB.

    Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com>
    ---
    Documentation/kernel-parameters.txt | 2 ++
    arch/powerpc/include/asm/pci.h | 2 ++
    drivers/pci/pci.c | 64 +++++++++++++++++++++++++++++------
    3 files changed, 57 insertions(+), 11 deletions(-)

    diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
    index d8b29ab..542be4a 100644
    --- a/Documentation/kernel-parameters.txt
    +++ b/Documentation/kernel-parameters.txt
    @@ -2918,6 +2918,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
    aligned memory resources.
    If <order of align> is not specified,
    PAGE_SIZE is used as alignment.
    + <domain>, <bus>, <slot> and <func> can be set to
    + "*" which means match all values.
    PCI-PCI bridge can be specified, if resource
    windows need to be expanded.
    noresize: Don't change the resources' sizes when
    diff --git a/arch/powerpc/include/asm/pci.h b/arch/powerpc/include/asm/pci.h
    index 6f8065a..78f230f 100644
    --- a/arch/powerpc/include/asm/pci.h
    +++ b/arch/powerpc/include/asm/pci.h
    @@ -30,6 +30,8 @@
    #define PCIBIOS_MIN_IO 0x1000
    #define PCIBIOS_MIN_MEM 0x10000000

    +#define PCIBIOS_MIN_ALIGNMENT PAGE_SIZE
    +
    struct pci_dev;

    /* Values for the `which' argument to sys_pciconfig_iobase syscall. */
    diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
    index 7271ce3..b690bc9 100644
    --- a/drivers/pci/pci.c
    +++ b/drivers/pci/pci.c
    @@ -4605,7 +4605,12 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
    int seg, bus, slot, func, align_order, count;
    resource_size_t align = 0;
    char *p;
    + bool invalid = false;

    +#ifdef PCIBIOS_MIN_ALIGNMENT
    + align = PCIBIOS_MIN_ALIGNMENT;
    + *resize = false;
    +#endif
    spin_lock(&resource_alignment_lock);
    p = resource_alignment_param;
    while (*p) {
    @@ -4622,16 +4627,49 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
    } else {
    align_order = -1;
    }
    - if (sscanf(p, "%x:%x:%x.%x%n",
    - &seg, &bus, &slot, &func, &count) != 4) {
    + if (p[0] == '*' && p[1] == ':') {
    + seg = -1;
    + count = 1;
    + } else if (sscanf(p, "%x%n", &seg, &count) != 1 ||
    + p[count] != ':') {
    + invalid = true;
    + break;
    + }
    + p += count + 1;
    + if (*p == '*') {
    + bus = -1;
    + count = 1;
    + } else if (sscanf(p, "%x%n", &bus, &count) != 1) {
    + invalid = true;
    + break;
    + }
    + p += count;
    + if (*p == '.') {
    + slot = bus;
    + bus = seg;
    seg = 0;
    - if (sscanf(p, "%x:%x.%x%n",
    - &bus, &slot, &func, &count) != 3) {
    - /* Invalid format */
    - printk(KERN_ERR "PCI: Can't parse resource_alignment parameter: %s\n",
    - p);
    + p++;
    + } else if (*p == ':') {
    + p++;
    + if (p[0] == '*' && p[1] == '.') {
    + slot = -1;
    + count = 1;
    + } else if (sscanf(p, "%x%n", &slot, &count) != 1 ||
    + p[count] != '.') {
    + invalid = true;
    break;
    }
    + p += count + 1;
    + } else {
    + invalid = true;
    + break;
    + }
    + if (*p == '*') {
    + func = -1;
    + count = 1;
    + } else if (sscanf(p, "%x%n", &func, &count) != 1) {
    + invalid = true;
    + break;
    }
    p += count;
    if (!strncmp(p, ":noresize", 9)) {
    @@ -4639,10 +4677,10 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
    p += 9;
    } else
    *resize = true;
    - if (seg == pci_domain_nr(dev->bus) &&
    - bus == dev->bus->number &&
    - slot == PCI_SLOT(dev->devfn) &&
    - func == PCI_FUNC(dev->devfn)) {
    + if ((seg == pci_domain_nr(dev->bus) || seg == -1) &&
    + (bus == dev->bus->number || bus == -1) &&
    + (slot == PCI_SLOT(dev->devfn) || slot == -1) &&
    + (func == PCI_FUNC(dev->devfn) || func == -1)) {
    if (align_order == -1)
    align = PAGE_SIZE;
    else
    @@ -4652,10 +4690,14 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev,
    }
    if (*p != ';' && *p != ',') {
    /* End of param or invalid format */
    + invalid = true;
    break;
    }
    p++;
    }
    + if (invalid == true)
    + printk(KERN_ERR "PCI: Can't parse resource_alignment parameter:%s\n",
    + p);
    spin_unlock(&resource_alignment_lock);
    return align;
    }
    --
    1.7.9.5
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