[PATCH 5/6] xen/arm: exclude xen,reg{-cacheable} from domU extended regions

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

When a device is passed through to a dom0less domU, the
xen,reg{-cacheable} ranges may overlap with the extended regions. Remove
xen,reg{-cacheable} from extended regions.

Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
---
Not sure if we need a Fixes: tag, but if we do:
Fixes: 2a2447757b3c ("xen/arm: implement domU extended regions")

I investigated an alternate approach of parsing the partial device tree
again to scan for xen,reg{-cacheable} properties, but it resulted in
quite a lot of code duplication. Adding a rangeset pointer to "struct
kernel_info" has a much smaller diffstat, and then we avoid the need to
parse the partial device tree a second time.

I discovered this issue when booting a dom0less domU with a device
passed through. Partial device tree excerpt:

    passthrough {
        ... <snip> ...

        axi_uart16550_0: serial@a0001000 {
            clocks = <&uart_fixed_clk>;
            compatible = "ns16550a";
            interrupt-parent = <&gic>;
            interrupts = <0 89 4>;
            reg = <0x0 0xa0001000 0x0 0x1000>;
            reg-shift = <2>;

            xen,reg = <0x0 0xa0001000 0x00 0x1000 0x0 0xa0001000>;
            xen,path = "/amba_pl@0/serial@a0000000";
            xen,force-assign-without-iommu;
        };
    };

The domU was assigned an extended region overlapping with MMIO of the
passed through device:

(XEN) d1: extended region 0: 0xa0000000->0x100000000
(XEN) d1: extended region 1: 0x200000000->0xf000000000

The domU panicked when attempting to initialize the device:

[    3.490068] a0001000.serial: ttyS0 at MMIO 0xa0001000 (irq = 15, base_baud = 
6249375) is a 16550A
[    3.498843] Unable to handle kernel NULL pointer dereference at virtual 
address 0000000000000010
[    3.498853] Mem abort info:
[    3.498855]   ESR = 0x0000000096000044
[    3.498859]   EC = 0x25: DABT (current EL), IL = 32 bits
[    3.498864]   SET = 0, FnV = 0
[    3.498867]   EA = 0, S1PTW = 0
[    3.498870]   FSC = 0x04: level 0 translation fault
[    3.498874] Data abort info:
[    3.498876]   ISV = 0, ISS = 0x00000044, ISS2 = 0x00000000
[    3.498879]   CM = 0, WnR = 1, TnD = 0, TagAccess = 0
[    3.498884]   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[    3.498888] [0000000000000010] user address but active_mm is swapper
[    3.498894] Internal error: Oops: 0000000096000044 [#1] SMP
[    3.498899] Modules linked in:
[    3.498908] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.12.10-stew #1
[    3.498917] pstate: 400000c5 (nZcv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[    3.498924] pc : mem_serial_out+0x18/0x20
[    3.498936] lr : serial8250_do_set_mctrl+0x6c/0xc0
[    3.498943] sp : ffff800081bab6d0
[    3.498946] x29: ffff800081bab6d0 x28: ffff8000815e0dc8 x27: ffff000001c29c60
[    3.498957] x26: 0000000000000000 x25: ffff00000347b900 x24: ffff000005504c00
[    3.498968] x23: ffff00000347b800 x22: 0000000000000000 x21: ffff800081b69d78
[    3.498978] x20: ffff800081b69d78 x19: 0000000000000000 x18: ffffffffffffffff
[    3.498989] x17: 3d20647561625f65 x16: 736162202c353120 x15: 3d20717269282030
[    3.498999] x14: 3030313030306178 x13: ffff800081a21ff0 x12: 00000000000007fe
[    3.499010] x11: 00000000000002aa x10: ffff800081a4dff0 x9 : ffff800081a21ff0
[    3.499020] x8 : 00000000fffff7ff x7 : ffff800081a4dff0 x6 : 0000000000000008
[    3.499030] x5 : 0000000000000000 x4 : ffff800080797584 x3 : 0000000000000002
[    3.499040] x2 : 0000000000000000 x1 : 0000000000000010 x0 : 0000000000000000
[    3.499050] Call trace:
[    3.499053]  mem_serial_out+0x18/0x20
[    3.499059]  serial8250_set_mctrl+0x34/0x40
[    3.499065]  serial_core_register_port+0x534/0x7dc
[    3.499075]  serial_ctrl_register_port+0x10/0x1c
[    3.499084]  uart_add_one_port+0x10/0x1c
[    3.499092]  serial8250_register_8250_port+0x308/0x4c0
[    3.499102]  of_platform_serial_probe+0x2c4/0x48c
[    3.499110]  platform_probe+0x68/0xdc
[    3.499120]  really_probe+0xbc/0x298
[    3.499128]  __driver_probe_device+0x78/0x12c
[    3.499135]  driver_probe_device+0xdc/0x160
[    3.499142]  __driver_attach+0x94/0x19c
[    3.499149]  bus_for_each_dev+0x74/0xd0
[    3.499155]  driver_attach+0x24/0x30
[    3.499162]  bus_add_driver+0xe4/0x208
[    3.499168]  driver_register+0x60/0x128
[    3.499176]  __platform_driver_register+0x24/0x30
[    3.499184]  of_platform_serial_driver_init+0x1c/0x28
[    3.499192]  do_one_initcall+0x6c/0x1b0
[    3.499199]  kernel_init_freeable+0x178/0x258
[    3.499209]  kernel_init+0x20/0x1d0
[    3.499218]  ret_from_fork+0x10/0x20
[    3.499228] Code: f9400800 1ac32021 8b21c001 d50332bf (39000022)
[    3.499233] ---[ end trace 0000000000000000 ]---
[    3.499237] note: swapper/0[1] exited with irqs disabled
[    3.499247] Kernel panic - not syncing: Attempted to kill init! 
exitcode=0x0000000b
[    3.499251] SMP: stopping secondary CPUs
[    3.499284] Kernel Offset: disabled
[    3.499286] CPU features: 0x00,00000080,00200000,0200420b
[    3.499292] Memory Limit: none
[    3.792412] ---[ end Kernel panic - not syncing: Attempted to kill init! 
exitcode=0x0000000b ]---
---
 xen/arch/arm/dom0less-build.c     | 19 ++++++++++++++++++-
 xen/arch/arm/domain_build.c       | 13 ++++++++++++-
 xen/arch/arm/include/asm/kernel.h |  1 +
 3 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/dom0less-build.c b/xen/arch/arm/dom0less-build.c
index a356fc94fc4d..23178a801818 100644
--- a/xen/arch/arm/dom0less-build.c
+++ b/xen/arch/arm/dom0less-build.c
@@ -274,6 +274,14 @@ static int __init handle_passthrough_prop(struct 
kernel_info *kinfo,
     int res;
     paddr_t mstart, size, gstart;
 
+    if ( !kinfo->xen_reg_assigned )
+    {
+        kinfo->xen_reg_assigned = rangeset_new(NULL, NULL, 0);
+
+        if ( !kinfo->xen_reg_assigned )
+            return -ENOMEM;
+    }
+
     /* xen,reg specifies where to map the MMIO region */
     cell = (const __be32 *)xen_reg->data;
     len = fdt32_to_cpu(xen_reg->len) / ((address_cells * 2 + size_cells) *
@@ -315,6 +323,11 @@ static int __init handle_passthrough_prop(struct 
kernel_info *kinfo,
                    mstart, gstart);
             return -EFAULT;
         }
+
+        res = rangeset_add_range(kinfo->xen_reg_assigned, PFN_DOWN(gstart),
+                                 PFN_DOWN(gstart + size - 1));
+        if ( res )
+            return res;
     }
 
     /*
@@ -1006,7 +1019,11 @@ static int __init construct_domU(struct domain *d,
 
     domain_vcpu_affinity(d, node);
 
-    return alloc_xenstore_params(&kinfo);
+    rc = alloc_xenstore_params(&kinfo);
+
+    rangeset_destroy(kinfo.xen_reg_assigned);
+
+    return rc;
 }
 
 void __init create_domUs(void)
diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 3dcdd7a8c46f..da7c7c000f1f 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -1296,6 +1296,13 @@ static int __init find_domU_holes(const struct 
kernel_info *kinfo,
     if ( res )
         goto out;
 
+    if ( kinfo->xen_reg_assigned )
+    {
+        res = rangeset_subtract(mem_holes, kinfo->xen_reg_assigned);
+        if ( res )
+            goto out;
+    }
+
     res = rangeset_report_ranges(mem_holes, 0,
                                  PFN_DOWN((1ULL << p2m_ipa_bits) - 1),
                                  add_ext_regions, ext_regions);
@@ -2329,7 +2336,11 @@ static int __init construct_dom0(struct domain *d)
     if ( rc < 0 )
         return rc;
 
-    return construct_hwdom(&kinfo, NULL);
+    rc = construct_hwdom(&kinfo, NULL);
+
+    rangeset_destroy(kinfo.xen_reg_assigned);
+
+    return rc;
 }
 
 int __init construct_hwdom(struct kernel_info *kinfo,
diff --git a/xen/arch/arm/include/asm/kernel.h 
b/xen/arch/arm/include/asm/kernel.h
index bdc96f4c18eb..b3c2d50e1e3d 100644
--- a/xen/arch/arm/include/asm/kernel.h
+++ b/xen/arch/arm/include/asm/kernel.h
@@ -50,6 +50,7 @@ struct kernel_info {
 #ifdef CONFIG_STATIC_SHM
     struct shared_meminfo shm_mem;
 #endif
+    struct rangeset *xen_reg_assigned;
 
     /* kernel entry point */
     paddr_t entry;
-- 
2.49.0