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

[Kiryl Shutsemau <kas@kernel.org>]

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.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov