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[PATCH v5 05/22] liveupdate: kho: when live update add KHO image during kexec load

Pasha Tatashin posted 22 patches 3 months ago
There is a newer version of this series
[PATCH v5 05/22] liveupdate: kho: when live update add KHO image during kexec load
Posted by Pasha Tatashin 3 months ago 
In case KHO is driven from within kernel via live update, finalize will
always happen during reboot, so add the KHO image unconditionally.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
 kernel/liveupdate/kexec_handover.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index 9f0913e101be..b54ca665e005 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -15,6 +15,7 @@
 #include <linux/kexec_handover.h>
 #include <linux/libfdt.h>
 #include <linux/list.h>
+#include <linux/liveupdate.h>
 #include <linux/memblock.h>
 #include <linux/page-isolation.h>
 #include <linux/vmalloc.h>
@@ -1489,7 +1490,7 @@ int kho_fill_kimage(struct kimage *image)
 	int err = 0;
 	struct kexec_buf scratch;
 
-	if (!kho_out.finalized)
+	if (!kho_out.finalized && !liveupdate_enabled())
 		return 0;
 
 	image->kho.fdt = virt_to_phys(kho_out.fdt);
-- 
2.51.2.1041.gc1ab5b90ca-goog
Re: [PATCH v5 05/22] liveupdate: kho: when live update add KHO image during kexec load
Posted by Mike Rapoport 3 months ago 
On Fri, Nov 07, 2025 at 04:03:03PM -0500, Pasha Tatashin wrote:
> In case KHO is driven from within kernel via live update, finalize will
> always happen during reboot, so add the KHO image unconditionally.
> 
> Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> ---
>  kernel/liveupdate/kexec_handover.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> index 9f0913e101be..b54ca665e005 100644
> --- a/kernel/liveupdate/kexec_handover.c
> +++ b/kernel/liveupdate/kexec_handover.c
> @@ -15,6 +15,7 @@
>  #include <linux/kexec_handover.h>
>  #include <linux/libfdt.h>
>  #include <linux/list.h>
> +#include <linux/liveupdate.h>
>  #include <linux/memblock.h>
>  #include <linux/page-isolation.h>
>  #include <linux/vmalloc.h>
> @@ -1489,7 +1490,7 @@ int kho_fill_kimage(struct kimage *image)
>  	int err = 0;
>  	struct kexec_buf scratch;
>  
> -	if (!kho_out.finalized)
> +	if (!kho_out.finalized && !liveupdate_enabled())
>  		return 0;

This feels backwards, I don't think KHO should call liveupdate methods.
  
>  	image->kho.fdt = virt_to_phys(kho_out.fdt);
> -- 
> 2.51.2.1041.gc1ab5b90ca-goog
> 

-- 
Sincerely yours,
Mike.
Re: [PATCH v5 05/22] liveupdate: kho: when live update add KHO image during kexec load
Posted by Pasha Tatashin 3 months ago 
On Mon, Nov 10, 2025 at 7:47 AM Mike Rapoport <rppt@kernel.org> wrote:
>
> On Fri, Nov 07, 2025 at 04:03:03PM -0500, Pasha Tatashin wrote:
> > In case KHO is driven from within kernel via live update, finalize will
> > always happen during reboot, so add the KHO image unconditionally.
> >
> > Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> > ---
> >  kernel/liveupdate/kexec_handover.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> > index 9f0913e101be..b54ca665e005 100644
> > --- a/kernel/liveupdate/kexec_handover.c
> > +++ b/kernel/liveupdate/kexec_handover.c
> > @@ -15,6 +15,7 @@
> >  #include <linux/kexec_handover.h>
> >  #include <linux/libfdt.h>
> >  #include <linux/list.h>
> > +#include <linux/liveupdate.h>
> >  #include <linux/memblock.h>
> >  #include <linux/page-isolation.h>
> >  #include <linux/vmalloc.h>
> > @@ -1489,7 +1490,7 @@ int kho_fill_kimage(struct kimage *image)
> >       int err = 0;
> >       struct kexec_buf scratch;
> >
> > -     if (!kho_out.finalized)
> > +     if (!kho_out.finalized && !liveupdate_enabled())
> >               return 0;
>
> This feels backwards, I don't think KHO should call liveupdate methods.

It is backward, but it is a requirement until KHO becomes stateless.
LUO does not have dependencies on userspace state of when kexec is
loaded. In fact the next kernel must be loaded before the brownout as
it is an expensive operation. The sequence of events should:

1. Load the next kernel in memory
2. Preserve resources via LUO
3. Do Kexec reboot

Pasha
Re: [PATCH v5 05/22] liveupdate: kho: when live update add KHO image during kexec load
Posted by Mike Rapoport 3 months ago 
On Mon, Nov 10, 2025 at 10:31:23AM -0500, Pasha Tatashin wrote:
> On Mon, Nov 10, 2025 at 7:47 AM Mike Rapoport <rppt@kernel.org> wrote:
> >
> > On Fri, Nov 07, 2025 at 04:03:03PM -0500, Pasha Tatashin wrote:
> > > In case KHO is driven from within kernel via live update, finalize will
> > > always happen during reboot, so add the KHO image unconditionally.
> > >
> > > Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
> > > ---
> > >  kernel/liveupdate/kexec_handover.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
> > > index 9f0913e101be..b54ca665e005 100644
> > > --- a/kernel/liveupdate/kexec_handover.c
> > > +++ b/kernel/liveupdate/kexec_handover.c
> > > @@ -15,6 +15,7 @@
> > >  #include <linux/kexec_handover.h>
> > >  #include <linux/libfdt.h>
> > >  #include <linux/list.h>
> > > +#include <linux/liveupdate.h>
> > >  #include <linux/memblock.h>
> > >  #include <linux/page-isolation.h>
> > >  #include <linux/vmalloc.h>
> > > @@ -1489,7 +1490,7 @@ int kho_fill_kimage(struct kimage *image)
> > >       int err = 0;
> > >       struct kexec_buf scratch;
> > >
> > > -     if (!kho_out.finalized)
> > > +     if (!kho_out.finalized && !liveupdate_enabled())
> > >               return 0;
> >
> > This feels backwards, I don't think KHO should call liveupdate methods.
> 
> It is backward, but it is a requirement until KHO becomes stateless.
> LUO does not have dependencies on userspace state of when kexec is
> loaded. In fact the next kernel must be loaded before the brownout as
> it is an expensive operation. The sequence of events should:
> 
> 1. Load the next kernel in memory
> 2. Preserve resources via LUO
> 3. Do Kexec reboot

I believe that when my concerns about "[PATCH v5 02/22] liveupdate:
luo_core: integrate with KHO" [1] are resolved this patch won't be needed.

[1] https://lore.kernel.org/all/aROZi043lxtegqWE@kernel.org/
 
> Pasha

-- 
Sincerely yours,
Mike.
Re: [PATCH v5 05/22] liveupdate: kho: when live update add KHO image during kexec load
Posted by Pasha Tatashin 3 months ago 
> I believe that when my concerns about "[PATCH v5 02/22] liveupdate:
> luo_core: integrate with KHO" [1] are resolved this patch won't be needed.
>
> [1] https://lore.kernel.org/all/aROZi043lxtegqWE@kernel.org/

Thank you, I replied to your comments in that patch. However, until
KHO becomes statless this change is needed. We *must* have KHO image
as part of kexec load if liveupdate=1.

>
> > Pasha
>
> --
> Sincerely yours,
> Mike.

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