Re: [PATCH v2 6/6] efi: respect the poisoned pages coming from previous kernel

[Breno Leitao <leitao@debian.org>]

On Fri, Aug 21, 2026 at 03:53:32PM +0100, Kiryl Shutsemau wrote:
> On Fri, Aug 21, 2026 at 07:03:06AM -0700, Breno Leitao wrote:
> > On Fri, Aug 21, 2026 at 01:13:55PM +0100, Kiryl Shutsemau wrote:
> > > On Fri, Aug 21, 2026 at 03:06:06AM -0700, Breno Leitao wrote:
> > > > +	/* Reserve the table itself so it survives a further kexec. */
> > > > +	memblock_reserve(PAGE_ALIGN_DOWN(ppm),
> > > > +			 PAGE_ALIGN(ppm + sizeof(*pm) + bitmap_size) -
> > > > +			 PAGE_ALIGN_DOWN(ppm));
> > > 
> > > Hm. I don't think it is enough.
> > > 
> > > On x86, kernel doesn't keep memblock around after boot (see
> > > CONFIG_ARCH_KEEP_MEMBLOCK). Reserving in memblock exclude the memory
> > > from page allocator. But kexec can place the image there.
> > 
> > You mean the third kexec?
> > 
> > 1) Kernel A hits an ECC error and marks page X poisoned.
> > 2) Kernel A kexecs into kernel B, which won't use that page since
> >    it's in EFI_POISONED_PAGE and memblock-reserved.
> > 3) Kernel B kexecs into kernel C, which doesn't respect
> >    EFI_POISONED_PAGE.
> > 
> > Is this the scenario you mean?
> 
> No. I think nothing prevents kernel B from putting kernel C image into
> the reserved space in !CONFIG_ARCH_KEEP_MEMBLOCK case.
> 
> Kernel B excludes poisoned memory from buddy allocator, but kexec
> doesn't care about this when look for placement for the next image.

Right, that is exactly the case I meant above — sorry for not being
clearer.

Agreed, this is a gap.

Can we keep it separate for now and address it as a follow-up? Similar
to the one covered the initial issue [1] first.

Link: https://lore.kernel.org/all/20260812-kexec_posioned-v6-0-e477887086f0@debian.org/ [1]