Re: [Xen-devel] [PATCH] support HVM guests with more than 3.75G memory

[Steven Hand <Steven.Hand@xxxxxxxxxxxx>]

>>So our HVM e820 table should also comply to this, and the 256M RAM that
>>falls into that range should be moved to 4G above, that's the "real
>>changes" in my patch.
>
>Thanks, I saw it's checked in as changeset 11186.
>
>But it can not work with shadow2, when I assigned 4096M memory, I got:
>
>(XEN) ----[ Xen-3.0-unstable    Not tainted ]----
>(XEN) CPU:    3
>(XEN) RIP:    e010:[<ffff83000013c267>]
>sh2_guess_wrmap__shadow_3_guest_3+0x67/0xd0
>(XEN) RFLAGS: 0000000000010202   CONTEXT: hypervisor
>(XEN) rax: ffff8140c0000000   rbx: 00000000001aed0d   rcx:
>00000000e8000001
>(XEN) rdx: 0000000000000aa2   rsi: 000000015448d000   rdi:
>ffff8300001a0080
>(XEN) rbp: ffff8300001a0080   rsp: ffff83000023fc98   r8:
>00000000001aed0d
>(XEN) r9:  0000000000000000   r10: 0000000000000000   r11:
>0000000000000000
>(XEN) r12: ffff828404350a08   r13: 0000000000000001   r14:
>00000000c0881008
>(XEN) r15: 0000000004350a08   cr0: 000000008005003b   cr3:
>0000000080b7f000
>(XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: 0000   cs: e010

Interesting - the crash is in the [optional] 'guess_wrmap' function
which is trying to fast path the lookup of a particular va.  Can you 
try temporarily disabling this optimization and retrying? Just edit 
xen/include/asm-x86/shadow2.c to replace 

#define SHADOW2_OPTIMZATIONS 0x03 

with 

#define SHADOW2_OPTIMZATIONS 0x02 


and recompile. 

It'd also be good to see if you can reproduce the above error on a 
guest with < 4G memory. 


I'll try to take a more detailed look myself when I get a test box 
sorted out. 


cheers,


S.

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