From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Date: Tue, 5 Oct 2021 17:35:57 -0700 From: Mike Rapoport Subject: Re: [PATCH v2 2/5] memblock: improve MEMBLOCK_HOTPLUG documentation Message-ID: References: <20211004093605.5830-1-david@redhat.com> <20211004093605.5830-3-david@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20211004093605.5830-3-david@redhat.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, Andrew Morton , Michal Hocko , Oscar Salvador , Jianyong Wu , "Aneesh Kumar K . V" , Vineet Gupta , Geert Uytterhoeven , Huacai Chen , Jiaxun Yang , Thomas Bogendoerfer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Eric Biederman , Arnd Bergmann , linux-snps-arc@lists.infradead.org, linux-ia64@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-s390@vger.kernel.org, linux-mm@kvack.org, kexec@lists.infradead.org On Mon, Oct 04, 2021 at 11:36:02AM +0200, David Hildenbrand wrote: > The description of MEMBLOCK_HOTPLUG is currently short and consequently > misleading: we're actually dealing with a memory region that might get > hotunplugged later (i.e., the platform+firmware supports it), yet it is > indicated in the firmware-provided memory map as system ram that will just > get used by the system for any purpose when not taking special care. The > firmware marked this memory region as a hot(un)plugged (e.g., hotplugged > before reboot), implying that it might get hotunplugged again later. > > Whether we consider this information depends on the "movable_node" kernel > commandline parameter: only with "movable_node" set, we'll try keeping > this memory hotunpluggable, for example, by not serving early allocations > from this memory region and by letting the buddy manage it using the > ZONE_MOVABLE. > > Let's make this clearer by extending the documentation. > > Note: kexec *has to* indicate this memory to the second kernel. With > "movable_node" set, we don't want to place kexec-images on this memory. > Without "movable_node" set, we don't care and can place kexec-images on > this memory. In both cases, after successful memory hotunplug, kexec has to > be re-armed to update the memory map for the second kernel and to place the > kexec-images somewhere else. > > Signed-off-by: David Hildenbrand Reviewed-by: Mike Rapoport > --- > include/linux/memblock.h | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/include/linux/memblock.h b/include/linux/memblock.h > index 34de69b3b8ba..4ee8dd2d63a7 100644 > --- a/include/linux/memblock.h > +++ b/include/linux/memblock.h > @@ -28,7 +28,11 @@ extern unsigned long long max_possible_pfn; > /** > * enum memblock_flags - definition of memory region attributes > * @MEMBLOCK_NONE: no special request > - * @MEMBLOCK_HOTPLUG: hotpluggable region > + * @MEMBLOCK_HOTPLUG: memory region indicated in the firmware-provided memory > + * map during early boot as hot(un)pluggable system RAM (e.g., memory range > + * that might get hotunplugged later). With "movable_node" set on the kernel > + * commandline, try keeping this memory region hotunpluggable. Does not apply > + * to memblocks added ("hotplugged") after early boot. > * @MEMBLOCK_MIRROR: mirrored region > * @MEMBLOCK_NOMAP: don't add to kernel direct mapping and treat as > * reserved in the memory map; refer to memblock_mark_nomap() description > -- > 2.31.1 > -- Sincerely yours, Mike. _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec