Re: [PATCH v1 1/5] console: add relocation hook

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Thu, Jun 05, 2025 at 04:42:53PM +0200, Jan Beulich wrote:
> On 26.05.2025 17:39, Marek Marczykowski-Górecki wrote:
> > On Mon, May 26, 2025 at 04:08:17PM +0100, Andrew Cooper wrote:
> >> On 25/05/2025 3:15 pm, Marek Marczykowski-Górecki wrote:
> >>> diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
> >>> index 25189541244d..3ef819a252e4 100644
> >>> --- a/xen/arch/x86/setup.c
> >>> +++ b/xen/arch/x86/setup.c
> >>> @@ -1481,6 +1481,8 @@ void asmlinkage __init noreturn __start_xen(void)
> >>>          highmem_start &= ~((1UL << L3_PAGETABLE_SHIFT) - 1);
> >>>  #endif
> >>>  
> >>> +    console_init_pre_relocate();
> >>> +
> >>>      /*
> >>>       * Iterate backwards over all superpage-aligned RAM regions.
> >>>       *
> >>> @@ -1606,6 +1608,12 @@ void asmlinkage __init noreturn __start_xen(void)
> >>>      if ( !xen_phys_start )
> >>>          panic("Not enough memory to relocate Xen\n");
> >>>  
> >>> +    /*
> >>> +     * Notify console drivers about relocation, before reusing old Xen's
> >>> +     * memory.
> >>> +     */
> >>> +    console_init_post_relocate();
> >>> +
> >>
> >> With reference to the next patch, there are printk()'s in this region
> >> which want to work (in case something goes very wrong), so I don't think
> >> setting dbc->suspended is the best approach.
> > 
> > I guess the post_relocate hook might be moved a bit earlier, but still,
> > once relocation happens, the xhci console is not functional until it
> > gets relocated too (for example - it would post new TRBs into a ring
> > that isn't actually monitored by the controller).
> 
> Why is it that this ring is dependent upon Xen's position? If the ring was
> dynamically allocated, it wouldn't change position when Xen is moved.

The console is setup quite early, I don't think I can allocate memory at
this stage, no?

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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