Re: [Xen-devel] debian stretch dom0 + xen 4.9 fails to boot

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

For those following this...

By poking characters at the screen and bisecting where they stopped, I have 
narrowed the problem to the code in edd.S. I can successfully boot by setting 
opt_edd=off on the Xen cmd line and I can also boot with the following patch 
applied:

diff --git a/xen/arch/x86/boot/edd.S b/xen/arch/x86/boot/edd.S
index 73371f98b5..5409f1d9a1 100644
--- a/xen/arch/x86/boot/edd.S
+++ b/xen/arch/x86/boot/edd.S
@@ -148,5 +148,6 @@ GLOBAL(boot_mbr_signature_nr)
         .byte   0
 GLOBAL(boot_mbr_signature)
         .fill   EDD_MBR_SIG_MAX*8,1,0
+       .align  4096
 GLOBAL(boot_edd_info)
-        .fill   512,1,0                         # big enough for a disc sector
+        .fill   4096,1,0                         # big enough for a disc sector

(based on a hunch that the BIOS defaults to a 4K sector for my NVMe drive)

I need to investigate some more but I do wonder whether the EDD info should be 
read first to determine the appropriate size of memory buffer to use when 
issuing the read of the MBR. Hardcoding a 4k reservation seems like the wrong 
thing to do, even if it is sufficient for this BIOS.

  Paul

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