Re: [REGRESSION] Linux 6.6.64 crashes when booting as PVH domU

[Ard Biesheuvel <ardb@xxxxxxxxxx>]

On Wed, 11 Dec 2024 at 12:53, Jürgen Groß <jgross@xxxxxxxx> wrote:
>
> Jason, Ard,
>
> I guess there are some prereq patches missing in stable 6.6.y branch?
>
>
> Juergen
>
> On 11.12.24 12:41, Marek Marczykowski-Górecki wrote:
> > Hi,
> >
> > With Linux 6.6.64 I get the following crash on domU boot:
> >
> > (XEN) d5v0 Triple fault - invoking HVM shutdown action 1
> > (XEN) *** Dumping Dom5 vcpu#0 state: ***
> > (XEN) ----[ Xen-4.19.0  x86_64  debug=n  Tainted:  M     ]----
> > (XEN) CPU:    4
> > (XEN) RIP:    0008:[<ffffffff82b64050>]
> > (XEN) RFLAGS: 0000000000010086   CONTEXT: hvm guest (d5v0)
> > (XEN) rax: ffffffff82b64050   rbx: ffffffffffe00000   rcx: 00000000c0000101
> > (XEN) rdx: 0000000000000000   rsi: 0000000003a00038   rdi: 0000000002a9bc98
> > (XEN) rbp: 0000000000000000   rsp: 0000000002aa0ce8   r8:  0000000000000000
> > (XEN) r9:  0000000000000000   r10: 0000000000000000   r11: 0000000000000000
> > (XEN) r12: 0000000000000000   r13: 0000000000000000   r14: 0000000000000000
> > (XEN) r15: 0000000000000000   cr0: 0000000080000011   cr4: 0000000000000020
> > (XEN) cr3: 0000000002022000   cr2: 0000000000000000
> > (XEN) fsb: 0000000000000000   gsb: 0000000002a9ccc0   gss: 0000000000000000
> > (XEN) ds: 0010   es: 0010   fs: 0000   gs: 0000   ss: 0010   cs: 0008
> >
> > Linux 6.6.63 works fine.
> >
> > Looking at the changes, I suspect one of those:
> >
> >      83d123e27623 x86/pvh: Call C code via the kernel virtual mapping
> >      f662b4a69e1d x86/pvh: Set phys_base when calling xen_prepare_pvh()
> >

The second patch shouldn't have been backported. It is unnecessary,
given that in the old situation, the kernel image needs to be loaded
at a fixed address. And it assumes  that %rbp is set to the physical
load offset, but those patches were not backported.