| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <61102a92-ad98-4fbd-bee8-760a758b0eb6@oss.qualcomm.com>
Date: Tue, 16 Dec 2025 14:21:40 -0800
From: Oreoluwa Babatunde <oreoluwa.babatunde@....qualcomm.com>
To: Rob Herring <robh@...nel.org>
Cc: m.szyprowski@...sung.com, ye.li@....nxp.com, kernel@....qualcomm.com,
saravanak@...gle.com, akpm@...ux-foundation.org, david@...hat.com,
lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com, vbabka@...e.cz,
rppt@...nel.org, surenb@...gle.com, mhocko@...e.com,
robin.murphy@....com, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
iommu@...ts.linux.dev, quic_c_gdjako@...cinc.com
Subject: Re: [PATCH] of: reserved_mem: Allow reserved_mem framework detect
"cma=" kernel param
Hi Rob,
On 12/10/2025 6:07 AM, Rob Herring wrote:
> On Tue, Dec 9, 2025 at 6:20 PM Oreoluwa Babatunde
> <oreoluwa.babatunde@....qualcomm.com> wrote:
>>
>> When initializing the default cma region, the "cma=" kernel parameter
>> takes priority over a DT defined linux,cma-default region. Hence, give
>> the reserved_mem framework the ability to detect this so that the DT
>> defined cma region can skip initialization accordingly.
>
> Please explain here why this is a new problem. Presumably the
> RESERVEDMEM_OF_DECLARE hook after commit xxxx gets called before the
> early_param hook. And why is it now earlier?
ACK. I will add more of this info in the next patch version.
>
> I don't really like the state/ordering having to be worried about in 2 places.
The advantage to having the state visible to the reserved_mem code is that
we can skip adding the DT node to the resrved_mem array since it actually
won't be used.
If this is still not preferred, another option would be to use a helper
function in contiguous.c to call dma_contiguous_early_fixup() for the
reserved_mem code. This way, "size_cmdline" can be checked internally within
the file and it can call dma_contiguous_early_fixup based on that.
>
>> Signed-off-by: Oreoluwa Babatunde <oreoluwa.babatunde@....qualcomm.com>
>> ---
>> drivers/of/of_reserved_mem.c | 19 +++++++++++++++++--
>> include/linux/cma.h | 1 +
>> kernel/dma/contiguous.c | 16 ++++++++++------
>> 3 files changed, 28 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/of/of_reserved_mem.c b/drivers/of/of_reserved_mem.c
>> index 2e9ea751ed2d..bef68a4916b5 100644
>> --- a/drivers/of/of_reserved_mem.c
>> +++ b/drivers/of/of_reserved_mem.c
>> @@ -158,7 +158,7 @@ static int __init __reserved_mem_reserve_reg(unsigned long node,
>> phys_addr_t base, size;
>> int len;
>> const __be32 *prop;
>> - bool nomap;
>> + bool nomap, default_cma;
>>
>> prop = of_get_flat_dt_prop(node, "reg", &len);
>> if (!prop)
>> @@ -171,6 +171,12 @@ static int __init __reserved_mem_reserve_reg(unsigned long node,
>> }
>>
>> nomap = of_get_flat_dt_prop(node, "no-map", NULL) != NULL;
>> + default_cma = of_get_flat_dt_prop(node, "linux,cma-default", NULL);
>> +
>> + if (default_cma && cma_skip_dt_default_reserved_mem()) {
>> + pr_err("Skipping dt linux,cma-default for \"cma=\" kernel param.\n");
>> + return -EINVAL;
>> + }
>>
>> while (len >= t_len) {
>> base = dt_mem_next_cell(dt_root_addr_cells, &prop);
>> @@ -256,12 +262,15 @@ void __init fdt_scan_reserved_mem_reg_nodes(void)
>>
>> fdt_for_each_subnode(child, fdt, node) {
>> const char *uname;
>> + bool default_cma = of_get_flat_dt_prop(child, "linux,cma-default", NULL);
>>
>> prop = of_get_flat_dt_prop(child, "reg", &len);
>> if (!prop)
>> continue;
>> if (!of_fdt_device_is_available(fdt, child))
>> continue;
>> + if (default_cma && cma_skip_dt_default_reserved_mem())
>> + continue;
>>
>> uname = fdt_get_name(fdt, child, NULL);
>> if (len && len % t_len != 0) {
>> @@ -406,7 +415,7 @@ static int __init __reserved_mem_alloc_size(unsigned long node, const char *unam
>> phys_addr_t base = 0, align = 0, size;
>> int len;
>> const __be32 *prop;
>> - bool nomap;
>> + bool nomap, default_cma;
>> int ret;
>>
>> prop = of_get_flat_dt_prop(node, "size", &len);
>> @@ -430,6 +439,12 @@ static int __init __reserved_mem_alloc_size(unsigned long node, const char *unam
>> }
>>
>> nomap = of_get_flat_dt_prop(node, "no-map", NULL) != NULL;
>> + default_cma = of_get_flat_dt_prop(node, "linux,cma-default", NULL);
>> +
>> + if (default_cma && cma_skip_dt_default_reserved_mem()) {
>> + pr_err("Skipping dt linux,cma-default for \"cma=\" kernel param.\n");
>> + return -EINVAL;
>> + }
>>
>> /* Need adjust the alignment to satisfy the CMA requirement */
>> if (IS_ENABLED(CONFIG_CMA)
>> diff --git a/include/linux/cma.h b/include/linux/cma.h
>> index 62d9c1cf6326..3d3047029950 100644
>> --- a/include/linux/cma.h
>> +++ b/include/linux/cma.h
>> @@ -47,6 +47,7 @@ extern int cma_init_reserved_mem(phys_addr_t base, phys_addr_t size,
>> unsigned int order_per_bit,
>> const char *name,
>> struct cma **res_cma);
>> +extern bool cma_skip_dt_default_reserved_mem(void);
>> extern struct page *cma_alloc(struct cma *cma, unsigned long count, unsigned int align,
>> bool no_warn);
>> extern bool cma_pages_valid(struct cma *cma, const struct page *pages, unsigned long count);
>> diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
>> index d9b9dcba6ff7..9071c08650e3 100644
>> --- a/kernel/dma/contiguous.c
>> +++ b/kernel/dma/contiguous.c
>> @@ -90,6 +90,16 @@ static int __init early_cma(char *p)
>> }
>> early_param("cma", early_cma);
>>
>> +/*
>> + * cma_skip_dt_default_reserved_mem - This is called from the
>> + * reserved_mem framework to detect if the default cma region is being
>> + * set by the "cma=" kernel parameter.
>> + */
>> +bool __init cma_skip_dt_default_reserved_mem(void)
>> +{
>> + return size_cmdline != -1;
>> +}
>> +
>> #ifdef CONFIG_DMA_NUMA_CMA
>>
>> static struct cma *dma_contiguous_numa_area[MAX_NUMNODES];
>> @@ -463,12 +473,6 @@ static int __init rmem_cma_setup(struct reserved_mem *rmem)
>> struct cma *cma;
>> int err;
>>
>> - if (size_cmdline != -1 && default_cma) {
>> - pr_info("Reserved memory: bypass %s node, using cmdline CMA params instead\n",
>> - rmem->name);
>> - return -EBUSY;
>> - }
>> -
>> if (!of_get_flat_dt_prop(node, "reusable", NULL) ||
>> of_get_flat_dt_prop(node, "no-map", NULL))
>> return -EINVAL;
>> --
>> 2.34.1
>>
>>
Regards,
Oreoluwa
Powered by blists - more mailing lists