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Wysocki" , Len Brown , Andrew Morton , David Hildenbrand , Oscar Salvador , Dan Williams , Dave Jiang , , , , , , Dave Hansen Subject: Re: [PATCH 3/3] dax/kmem: Always enroll hotplugged memory for memmap_on_memory References: <20230613-vv-kmem_memmap-v1-0-f6de9c6af2c6@intel.com> <20230613-vv-kmem_memmap-v1-3-f6de9c6af2c6@intel.com> Date: Fri, 16 Jun 2023 14:42:43 +0800 In-Reply-To: <20230613-vv-kmem_memmap-v1-3-f6de9c6af2c6@intel.com> (Vishal Verma's message of "Thu, 15 Jun 2023 16:00:25 -0600") Message-ID: <87zg4zewm4.fsf@yhuang6-desk2.ccr.corp.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii X-Rspamd-Queue-Id: 92F024000B X-Rspam-User: X-Stat-Signature: xmgxaprns7wshxgae8abreupsidn9rwu X-Rspamd-Server: rspam03 X-HE-Tag: 1686897857-775825 X-HE-Meta: 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 +0++qXkG kH5B4KwlbVGUqAGA67EMsIFvbQ+cwShAUs8C4hogWa18k3/JzXVVy/DqovgI3N7dQCbRF1X8XdUG/swXDuQ4DdeS9NUK1F62uRZ3pYieBniHy6598JjemXQPVvaHwvh2yTEyb1Y8b38RtTO8Bx6EVj5UauoDYqwRvW+COrZ6gJTUW0aCEbjjNx1R8iatr2VHvVbMQXC5t5qeq7diVxCFcdrr+C3xua04OkeYCeMMFsqaoBDxhHm7s0eE0fbKanz10LryYQEo9TA+2n2wAlbS2yMXAGrN7qvpJW/dwlwok7/RrT11hBxmx47yZXQb6sNWJGwxa9fA06P3XLIGzwcl6EBn/Zu9J+ftXeo9gNLpI5IkaveE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Vishal Verma writes: > With DAX memory regions originating from CXL memory expanders or > NVDIMMs, the kmem driver may be hot-adding huge amounts of system memory > on a system without enough 'regular' main memory to support the memmap > for it. To avoid this, ensure that all kmem managed hotplugged memory is > added with the MHP_MEMMAP_ON_MEMORY flag to place the memmap on the > new memory region being hot added. > > To do this, call add_memory() in chunks of memory_block_size_bytes() as > that is a requirement for memmap_on_memory. Additionally, Use the > mhp_flag to force the memmap_on_memory checks regardless of the > respective module parameter setting. > > Cc: "Rafael J. Wysocki" > Cc: Len Brown > Cc: Andrew Morton > Cc: David Hildenbrand > Cc: Oscar Salvador > Cc: Dan Williams > Cc: Dave Jiang > Cc: Dave Hansen > Cc: Huang Ying > Signed-off-by: Vishal Verma > --- > drivers/dax/kmem.c | 49 ++++++++++++++++++++++++++++++++++++------------- > 1 file changed, 36 insertions(+), 13 deletions(-) > > diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c > index 7b36db6f1cbd..0751346193ef 100644 > --- a/drivers/dax/kmem.c > +++ b/drivers/dax/kmem.c > @@ -12,6 +12,7 @@ > #include > #include > #include > +#include > #include "dax-private.h" > #include "bus.h" > > @@ -105,6 +106,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) > data->mgid = rc; > > for (i = 0; i < dev_dax->nr_range; i++) { > + u64 cur_start, cur_len, remaining; > struct resource *res; > struct range range; > > @@ -137,21 +139,42 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax) > res->flags = IORESOURCE_SYSTEM_RAM; > > /* > - * Ensure that future kexec'd kernels will not treat > - * this as RAM automatically. > + * Add memory in chunks of memory_block_size_bytes() so that > + * it is considered for MHP_MEMMAP_ON_MEMORY > + * @range has already been aligned to memory_block_size_bytes(), > + * so the following loop will always break it down cleanly. > */ > - rc = add_memory_driver_managed(data->mgid, range.start, > - range_len(&range), kmem_name, MHP_NID_IS_MGID); > + cur_start = range.start; > + cur_len = memory_block_size_bytes(); > + remaining = range_len(&range); > + while (remaining) { > + mhp_t mhp_flags = MHP_NID_IS_MGID; > > - if (rc) { > - dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n", > - i, range.start, range.end); > - remove_resource(res); > - kfree(res); > - data->res[i] = NULL; > - if (mapped) > - continue; > - goto err_request_mem; > + if (mhp_supports_memmap_on_memory(cur_len, > + MHP_MEMMAP_ON_MEMORY)) > + mhp_flags |= MHP_MEMMAP_ON_MEMORY; > + /* > + * Ensure that future kexec'd kernels will not treat > + * this as RAM automatically. > + */ > + rc = add_memory_driver_managed(data->mgid, cur_start, > + cur_len, kmem_name, > + mhp_flags); > + > + if (rc) { > + dev_warn(dev, > + "mapping%d: %#llx-%#llx memory add failed\n", > + i, cur_start, cur_start + cur_len - 1); > + remove_resource(res); > + kfree(res); > + data->res[i] = NULL; > + if (mapped) > + continue; > + goto err_request_mem; > + } > + > + cur_start += cur_len; > + remaining -= cur_len; > } > mapped++; > } It appears that we need to hot-remove memory in the granularity of memory_block_size_bytes() too, according to try_remove_memory(). If so, it seems better to allocate one dax_kmem_data.res[] element for each memory block instead of dax region? Best Regards, Huang, Ying