[PATCH] hvmloader: pass PCI MMIO layout to OVMF as an info table

[Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>]

We faced a problem with passing through a PCI device with 64GB BAR to
UEFI guest. The BAR is expectedly programmed into 64-bit PCI aperture at
64G address which pushes physical address space to 37 bits. OVMF uses
address width early in PEI phase to make DXE identity pages covering
the whole addressable space so it needs to know the last address it needs
to cover but at the same time not overdo the mappings.

As there is seemingly no other way to pass or get this information in
OVMF at this early phase (ACPI is not yet available, PCI is not yet enumerated,
xenstore is not yet initialized) - extend the info structure with a new
table. Since the structure was initially created to be extendable -
the change is backward compatible.

Signed-off-by: Igor Druzhinin <igor.druzhinin@xxxxxxxxxx>
---

Companion change in OVMF:
https://lists.xenproject.org/archives/html/xen-devel/2021-01/msg00516.html

---
 tools/firmware/hvmloader/ovmf.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tools/firmware/hvmloader/ovmf.c b/tools/firmware/hvmloader/ovmf.c
index 23610a0..9bfe274 100644
--- a/tools/firmware/hvmloader/ovmf.c
+++ b/tools/firmware/hvmloader/ovmf.c
@@ -61,6 +61,14 @@ struct ovmf_info {
     uint32_t e820_nr;
 } __attribute__ ((packed));
 
+#define OVMF_INFO_PCI_TABLE 0
+struct ovmf_pci_info {
+    uint64_t low_start;
+    uint64_t low_end;
+    uint64_t hi_start;
+    uint64_t hi_end;
+} __attribute__ ((packed));
+
 static void ovmf_setup_bios_info(void)
 {
     struct ovmf_info *info = (void *)OVMF_INFO_PHYSICAL_ADDRESS;
@@ -74,9 +82,21 @@ static void ovmf_setup_bios_info(void)
 static void ovmf_finish_bios_info(void)
 {
     struct ovmf_info *info = (void *)OVMF_INFO_PHYSICAL_ADDRESS;
+    struct ovmf_pci_info *pci_info;
+    uint64_t *tables = scratch_alloc(sizeof(uint64_t)*OVMF_INFO_MAX_TABLES, 0);
     uint32_t i;
     uint8_t checksum;
 
+    pci_info = scratch_alloc(sizeof(struct ovmf_pci_info), 0);
+    pci_info->low_start = pci_mem_start;
+    pci_info->low_end = pci_mem_end;
+    pci_info->hi_start = pci_hi_mem_start;
+    pci_info->hi_end = pci_hi_mem_end;
+
+    tables[OVMF_INFO_PCI_TABLE] = (uint32_t)pci_info;
+    info->tables = (uint32_t)tables;
+    info->tables_nr = 1;
+
     checksum = 0;
     for ( i = 0; i < info->length; i++ )
         checksum += ((uint8_t *)(info))[i];
-- 
2.7.4