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Re: [PATCH v1 3/6] xen/arm: create dom0less virtio-pci DT node



Hi,

On 24/09/2024 17:23, Edgar E. Iglesias wrote:
From: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>

When virtio-pci is specified in the dom0less domU properties, create a
virtio-pci node in the guest's device tree. Set up an mmio handler with
a register for the guest to poll when the backend has connected and
virtio-pci bus is ready to be probed. Grant tables may be used by
specifying virtio-pci = "grants";.

[Edgar: Use GPEX PCI INTX interrupt swizzling (from PCI specs).
  Make grants iommu-map cover the entire PCI bus.
  Add virtio-pci-ranges to specify memory-map for direct-mapped guests.
  Document virtio-pci dom0less fdt bindings.]
Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xxxxxxx>
---
  docs/misc/arm/device-tree/booting.txt |  21 +++
  xen/arch/arm/dom0less-build.c         | 238 ++++++++++++++++++++++++++
  xen/arch/arm/include/asm/kernel.h     |  15 ++
  3 files changed, 274 insertions(+)

diff --git a/docs/misc/arm/device-tree/booting.txt 
b/docs/misc/arm/device-tree/booting.txt
index 3a04f5c57f..82f3bd7026 100644
--- a/docs/misc/arm/device-tree/booting.txt
+++ b/docs/misc/arm/device-tree/booting.txt
@@ -276,6 +276,27 @@ with the following properties:
      passed through. This option is the default if this property is missing
      and the user does not provide the device partial device tree for the 
domain.
+- virtio-pci

Similar question to the other patches, why is this specific to virtio PCI? QEMU (or another device module) is free to emulate whatever it wants behind the PCI hosbtridge.

+
+    A string property specifying whether virtio-pci is enabled for the
+    domain and if grant table mappings should be used. If no value is set
+    this property is treated as a boolean and the same way as if set to
+    "enabled".
+    Possible property values are:
+
+    - "enabled"
+    Virtio-pci is enabled for the domain.
+
+    - "grants"
+    Virtio-pci is enabled for the domain and an grants IOMMU node will be
+    generated in the domains device-tree.
+
+- virtio-pci-ranges
+
+    An optional array of 6 u32 values specifying the 2 cells base addresses of
+    the ECAM, Memory and Prefetchable-Memory regions for virtio-pci. This is
+    useful to avoid memory-map collisions when using direct-mapped guests.
+
  Under the "xen,domain" compatible node, one or more sub-nodes are present
  for the DomU kernel and ramdisk.
diff --git a/xen/arch/arm/dom0less-build.c b/xen/arch/arm/dom0less-build.c
index 09b65e44ae..dab24fa9e2 100644
--- a/xen/arch/arm/dom0less-build.c
+++ b/xen/arch/arm/dom0less-build.c
@@ -586,6 +586,189 @@ static int __init domain_handle_dtb_bootmodule(struct 
domain *d,
      return res;
  }
+static int __init make_virtio_pci_domU_node(const struct kernel_info *kinfo)
+{
+    void *fdt = kinfo->fdt;
+    /* reg is sized to be used for all the needed properties below */
+    __be32 reg[(1 + (GUEST_ROOT_ADDRESS_CELLS * 2) + GUEST_ROOT_SIZE_CELLS)
+               * 2];
+    __be32 irq_map[4 * 4 * 8];
+    __be32 *cells;
+    char buf[22]; /* pcie@ + max 16 char address + '\0' */
+    int res;
+    int devfn, intx_pin;
+    static const char compat[] = "pci-host-ecam-generic";
+    static const char reg_names[] = "ecam";
+
+    if ( p2m_ipa_bits <= 40 ) {
+        printk("PA bits %d is too small!\nvirtio-pci is only supported "
+               "on platforms with PA bits > 40\n", p2m_ipa_bits);
+        return -EINVAL;
+    }

Please add a comment explaining where does this requires come from. If this is the Address layout, then probably be to avoid relying on hardcoded number of bits.

Cheers,

--
Julien Grall



 


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