[Xen-devel] Xen OVMF regression

[Wei Liu <wei.liu2@xxxxxxxxxx>]

Hi Anthony and Laszlo

The following commit caused Xen hvm guest failed to boot.

commit 66b280df282ae82888d2eb416bfeda3f65afa386
Author: Laszlo Ersek <lersek@xxxxxxxxxx>
Date:   Thu Nov 20 09:58:28 2014 +0000

    OvmfPkg: AcpiPlatformDxe: make dependency on PCI enumeration explicit

    The ACPI payload that OVMF downloads from QEMU via fw_cfg depends on the
    PCI enumaration and resource assignment performed by
    MdeModulePkg/Bus/Pci/PciBusDxe.

    ...

The patch itself is simple and well reasoned. I couldn't immediately see
the culprit that caused Xen guest to crash.

All this commit does is it changed dependency of a module. So I think
it triggered some sort of domino effect that affected other Xen
components. My bet is that there is some missing dependencies in those
two Xen modules (XenBusDxe and XenBlkDxe), but I can't say for sure.

After this patch, following errors showed up:

(d44)  BlockSize : 512
(d44)  LastBlock : 1E997FF
(d44) XenBus: BAR at F2000000
(XEN) multi.c:3322:d44v0 write to pagetable during event injection: 
cr2=0xeff62848, mfn=0x1d3b62
(XEN) multi.c:3322:d44v0 write to pagetable during event injection: 
cr2=0xeff62838, mfn=0x1d3b62

Eventually guest crashed with:

(XEN) sh error: sh_remove_shadows(): can't find all shadows of mfn 1d3b01 
(shadow_flags=00002000)
(XEN) domain_crash called from common.c:2645
(XEN) Domain 44 (vcpu#0) crashed on cpu#0:
(XEN) ----[ Xen-4.6-unstable  x86_64  debug=y  Tainted:    C ]----
(XEN) CPU:    0
(XEN) RIP:    0033:[<00007fb1c58b84f7>]
(XEN) RFLAGS: 0000000000010202   CONTEXT: hvm guest
(XEN) rax: 0000000000000003   rbx: 00007fff6f87ff00   rcx: 00007fb1c58bb6b1
(XEN) rdx: 00007fff6f87ff28   rsi: 00007fb1c58a64e0   rdi: 00007fff6f87ff08
(XEN) rbp: 00007fb1c58a64e0   rsp: 00007fff6f87fe50   r8:  0000000000000002
(XEN) r9:  0000000d6370025e   r10: 000000006fffff6a   r11: 000000006ffffeff
(XEN) r12: 00007fb1c58a4a78   r13: 00007fb1c58a4000   r14: 00007fb1c58a4a78
(XEN) r15: 00007fb1c58a4380   cr0: 000000008005003b   cr4: 00000000000006f0
(XEN) cr3: 00000000efa2a000   cr2: 00007fb1c5ac30d0
(XEN) ds: 0000   es: 0000   fs: 0000   gs: 0000   ss: 002b   cs: 0033

Any idea how this can be fixed?

Wei.

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