[PATCH for-4.19] libxl: fix population of the online vCPU bitmap for PVH

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

libxl passes some information to libacpi to create the ACPI table for a PVH
guest, and among that information it's a bitmap of which vCPUs are online
which can be less than the maximum number of vCPUs assigned to the domain.

While the population of the bitmap is done correctly for HVM based on the
number of online vCPUs, for PVH the population of the bitmap is done based on
the number of maximum vCPUs allowed.  This leads to all local APIC entries in
the MADT being set as enabled, which contradicts the data in xenstore if vCPUs
is different than maximum vCPUs.

Fix by copying the internal libxl bitmap that's populated based on the vCPUs
parameter.

Reported-by: Arthur Borsboom <arthurborsboom@xxxxxxxxx>
Link: https://gitlab.com/libvirt/libvirt/-/issues/399
Reported-by: Leigh Brown <leigh@xxxxxxxxxxxxx>
Fixes: 14c0d328da2b ('libxl/acpi: Build ACPI tables for HVMlite guests')
Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Note that the setup of hvm_info_table could be shared between PVH and HVM, as
the fields are very limited, see hvm_build_set_params() for the HVM side.
However this late in the release it's safer to just adjust the PVH path.

Also note the checksum is not provided when hvm_info_table is built for PVH.
This is fine so far because such checksum is only consumed by hvmloader and not
libacpi itself.

It's a bugfix, so should be considered for 4.19.
---
 tools/libs/light/libxl_x86_acpi.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/libs/light/libxl_x86_acpi.c 
b/tools/libs/light/libxl_x86_acpi.c
index 620f3c700c3e..5cf261bd6794 100644
--- a/tools/libs/light/libxl_x86_acpi.c
+++ b/tools/libs/light/libxl_x86_acpi.c
@@ -89,7 +89,7 @@ static int init_acpi_config(libxl__gc *gc,
     uint32_t domid = dom->guest_domid;
     xc_domaininfo_t info;
     struct hvm_info_table *hvminfo;
-    int i, r, rc;
+    int r, rc;
 
     config->dsdt_anycpu = config->dsdt_15cpu = dsdt_pvh;
     config->dsdt_anycpu_len = config->dsdt_15cpu_len = dsdt_pvh_len;
@@ -138,8 +138,8 @@ static int init_acpi_config(libxl__gc *gc,
         hvminfo->nr_vcpus = info.max_vcpu_id + 1;
     }
 
-    for (i = 0; i < hvminfo->nr_vcpus; i++)
-        hvminfo->vcpu_online[i / 8] |= 1 << (i & 7);
+    memcpy(hvminfo->vcpu_online, b_info->avail_vcpus.map,
+           b_info->avail_vcpus.size);
 
     config->hvminfo = hvminfo;
 
-- 
2.44.0