From: Tzung-Bi Shih <tzungbi@kernel.org>
To: Hsin-Te Yuan <yuanhsinte@chromium.org>
Cc: Brian Norris <briannorris@chromium.org>,
Julius Werner <jwerner@chromium.org>,
chrome-platform@lists.linux.dev, linux-kernel@vger.kernel.org,
Yidi Lin <yidilin@google.com>
Subject: Re: [PATCH] firmware: google: coreboot_table: skip no-map CBMEM entries
Date: Fri, 17 Jul 2026 07:59:51 +0000 [thread overview]
Message-ID: <alng9zHTD854NBk1@google.com> (raw)
In-Reply-To: <CAHc4DNJwVOa-j5D3SiSiXTzA8MGq9p_RxYHXjXSd1po=uDHPqw@mail.gmail.com>
On Fri, Jul 17, 2026 at 03:23:30PM +0800, Hsin-Te Yuan wrote:
> On Thu, Jul 16, 2026 at 3:44 PM Tzung-Bi Shih <tzungbi@kernel.org> wrote:
> >
> > On Tue, Jul 14, 2026 at 09:19:18AM +0000, Hsin-Te Yuan wrote:
> > > @@ -147,6 +149,23 @@ static int coreboot_table_populate(struct device *dev, void *ptr, resource_size_
> > >
> > > switch (device->entry.tag) {
> > > case LB_TAG_CBMEM_ENTRY:
> > > + /*
> > > + * Skip entries that are not exclusively System RAM or
> > > + * Reserved memory.
> > > + * On ARM, no-map reserved regions are not System RAM.
To be specific,
On ARM, no-map reserved regions are IORESOURCE_MEM.
> > > + * On x86, CBMEM often resides in IORES_DESC_RESERVED regions.
> > > + */
> > > + if (region_intersects(device->cbmem_entry.address,
> > > + device->cbmem_entry.entry_size,
> > > + IORESOURCE_SYSTEM_RAM,
> > > + IORES_DESC_NONE) != REGION_INTERSECTS &&
> > > + region_intersects(device->cbmem_entry.address,
> > > + device->cbmem_entry.entry_size,
> > > + IORESOURCE_MEM,
> > > + IORES_DESC_RESERVED) != REGION_INTERSECTS) {
> >
> > Per comments of region_intersects():
> > Note that REGION_INTERSECTS is also returned in the case when the
> > specified region overlaps RAM and undefined memory holes.
> >
> > Won't the check falsely be bypassed if the region overlaps SYSTEM_RAM
> > and `no-map` memory?
>
> Just discussed this with Yidi Lin.
> It seems that 'no-map' region will be marked as IORESOURCE_MEM instead
> of undefined memory holes
> (See arch/arm64/kernel/setup.c:request_standard_resources). If a cbmem
> entry contains a real memory
> hole, it is likely a coreboot bug.
I see.
Please rephrase the commit message and code comment to be clear. E.g.:
1. On ARM64, no-map regions are filtered out as they are IORESOURCE_MEM
(See arch/arm64/kernel/setup.c:request_standard_resources).
2. On X86, standard reserved regions (IORES_DESC_RESERVED) ...
3. Mixed regions containing holes are safely skipped.
Remove it as this is inaccurate (the patch can't skip holes).
prev parent reply other threads:[~2026-07-17 7:59 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-14 9:19 [PATCH] firmware: google: coreboot_table: skip no-map CBMEM entries Hsin-Te Yuan
2026-07-16 7:44 ` Tzung-Bi Shih
2026-07-17 7:23 ` Hsin-Te Yuan
2026-07-17 7:59 ` Tzung-Bi Shih [this message]
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