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Re: Porting Xen to Jetson Nano

On 22/07/2020 18:57, Srinivas Bangalore wrote:
Dear Xen experts,


Would greatly appreciate some hints on how to move forward with this one…

From your first set of original log:

> Xen version 4.8.5 (srinivas@) (aarch64-linux-gnu-gcc
> (Ubuntu/Linaro 7.5.0-3ubuntu1~18.04) 7.5.0) debug=n  Sun Jul 19 07:44:00
> PDT 2020

I would recommend to compile Xen with debug enabled (CONFIG_DEBUG=y) as it may provide you more information of what's happening.

Also, aside the Tegra series. Do you have any other patches on top?


(XEN) BANK[0] 0x000000a0000000-0x000000c0000000 (512MB)

(XEN) Grant table range: 0x000000fec00000-0x000000fec60000

(XEN) Loading zImage from 00000000e1000000 to 00000000a0080000-00000000a223c808

(XEN) Allocating PPI 16 for event channel interrupt

(XEN) Loading dom0 DTB to 0x00000000a8000000-0x00000000a803435c


(XEN) *** Dumping CPU0 guest state (d0v0): ***

(XEN) ----[ Xen-4.8.5  arm64  debug=n   Tainted:  C   ]----

(XEN) CPU:    0

(XEN) PC:     00000000a0080000

PC is pointing to the entry point of your kernel...

(XEN) LR:     0000000000000000

(XEN) SP_EL0: 0000000000000000

(XEN) SP_EL1: 0000000000000000

(XEN) CPSR:   000001c5 MODE:64-bit EL1h (Guest Kernel, handler)

(XEN)      X0: 00000000a8000000  X1: 0000000000000000  X2: 0000000000000000

(XEN)      X3: 0000000000000000  X4: 0000000000000000  X5: 0000000000000000

(XEN)      X6: 0000000000000000  X7: 0000000000000000  X8: 0000000000000000

(XEN)      X9: 0000000000000000 X10: 0000000000000000 X11: 0000000000000000

(XEN)     X12: 0000000000000000 X13: 0000000000000000 X14: 0000000000000000

(XEN)     X15: 0000000000000000 X16: 0000000000000000 X17: 0000000000000000

(XEN)     X18: 0000000000000000 X19: 0000000000000000 X20: 0000000000000000

(XEN)     X21: 0000000000000000 X22: 0000000000000000 X23: 0000000000000000

(XEN)     X24: 0000000000000000 X25: 0000000000000000 X26: 0000000000000000

(XEN)     X27: 0000000000000000 X28: 0000000000000000  FP: 0000000000000000


(XEN)    ELR_EL1: 0000000000000000

(XEN)    ESR_EL1: 00000000

(XEN)    FAR_EL1: 0000000000000000


(XEN)  SCTLR_EL1: 00c50838

(XEN)    TCR_EL1: 00000000

(XEN)  TTBR0_EL1: 0000000000000000

(XEN)  TTBR1_EL1: 0000000000000000


(XEN)   VTCR_EL2: 80043594

(XEN)  VTTBR_EL2: 000100017f0f9000


(XEN)  SCTLR_EL2: 30cd183d

(XEN)    HCR_EL2: 000000008038663f

(XEN)  TTBR0_EL2: 00000000fecfc000


(XEN)    ESR_EL2: 8200000d

... it looks like we are receiving a trap in EL2 because it can't execute the instruction. This is a bit odd as the p2m (stage-2 page-tables) should be configured to allow execution. It would be useful if you can dump the p2m walk here. This following patch should do the job (not compiled test):

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index d578a5c598dd..af1834cdf735 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2489,9 +2489,14 @@ static void do_trap_instr_abort_guest(struct cpu_user_regs *regs,
         rc = gva_to_ipa(gva, &gpa, GV2M_READ);
         if ( rc == -EFAULT )
+        {
+            printk("Unable to translate 0x%lx\n", gva);
             return; /* Try again */
+        }

+    dump_p2m_walk(current->domain, gpa);
     switch ( fsc )
     case FSC_FLT_PERM:

(XEN)  HPFAR_EL2: 0000000000000000

(XEN)    FAR_EL2: 00000000a0080000


(XEN) Guest stack trace from sp=0:

(XEN)   Failed to convert stack to physical address


It seems the DOM0 kernel did not get added to the task list….

From a look at the dump, dom0 vCPU0 has been scheduled and running on pCPU0.

Boot args for Xen and Dom0 are here:
(XEN) Checking for initrd in /chosen

(XEN) linux,initrd limits invalid: 0000000084100000 >= 0000000084100000

(XEN) RAM: 0000000080000000 - 00000000fedfffff

(XEN) RAM: 0000000100000000 - 000000017f1fffff


(XEN) MODULE[0]: 00000000fc7f8000 - 00000000fc82d000 Device Tree

(XEN) MODULE[1]: 00000000e1000000 - 00000000e31bc808 Kernel console=hvc0 earlyprintk=xen earlycon=xen rootfstype=ext4 rw rootwait root=/dev/mmcblk0p1 rdinit=/sbin/init

You want to use earlycon=xenboot here.

(XEN)  RESVD[0]: 0000000080000000 - 0000000080020000

(XEN)  RESVD[1]: 00000000e3500000 - 00000000e3535000

(XEN)  RESVD[2]: 00000000fc7f8000 - 00000000fc82d000


(XEN) Command line: console=dtuart earlyprintk=xen earlycon=uart8250,mmio32,0x70006000 sync_console dom0_mem=512M log_lvl=all guest_loglvl=all console_to_ring

FWIW, earlyprintk and earlycon are not understood by Xen. They are only useful for Dom0.

Best regards,

Julien Grall



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