Messages in this thread | | | Subject | Re: [PATCH v15 09/10] arm64: Call kmalloc() to allocate DTB buffer | From | Lakshmi Ramasubramanian <> | Date | Wed, 27 Jan 2021 20:33:34 -0800 |
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On 1/27/21 8:14 PM, Thiago Jung Bauermann wrote: > > Lakshmi Ramasubramanian <nramas@linux.microsoft.com> writes: > >> On 1/27/21 7:52 PM, Thiago Jung Bauermann wrote: >>> Will Deacon <will@kernel.org> writes: >>> >>>> On Wed, Jan 27, 2021 at 09:59:38AM -0800, Lakshmi Ramasubramanian wrote: >>>>> On 1/27/21 8:52 AM, Will Deacon wrote: >>>>> >>>>> Hi Will, >>>>> >>>>>> On Fri, Jan 15, 2021 at 09:30:16AM -0800, Lakshmi Ramasubramanian wrote: >>>>>>> create_dtb() function allocates kernel virtual memory for >>>>>>> the device tree blob (DTB). This is not consistent with other >>>>>>> architectures, such as powerpc, which calls kmalloc() for allocating >>>>>>> memory for the DTB. >>>>>>> >>>>>>> Call kmalloc() to allocate memory for the DTB, and kfree() to free >>>>>>> the allocated memory. >>>>>>> >>>>>>> Co-developed-by: Prakhar Srivastava <prsriva@linux.microsoft.com> >>>>>>> Signed-off-by: Prakhar Srivastava <prsriva@linux.microsoft.com> >>>>>>> Signed-off-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com> >>>>>>> --- >>>>>>> arch/arm64/kernel/machine_kexec_file.c | 12 +++++++----- >>>>>>> 1 file changed, 7 insertions(+), 5 deletions(-) >>>>>>> >>>>>>> diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c >>>>>>> index 7de9c47dee7c..51c40143d6fa 100644 >>>>>>> --- a/arch/arm64/kernel/machine_kexec_file.c >>>>>>> +++ b/arch/arm64/kernel/machine_kexec_file.c >>>>>>> @@ -29,7 +29,7 @@ const struct kexec_file_ops * const kexec_file_loaders[] = { >>>>>>> int arch_kimage_file_post_load_cleanup(struct kimage *image) >>>>>>> { >>>>>>> - vfree(image->arch.dtb); >>>>>>> + kfree(image->arch.dtb); >>>>>>> image->arch.dtb = NULL; >>>>>>> vfree(image->arch.elf_headers); >>>>>>> @@ -59,19 +59,21 @@ static int create_dtb(struct kimage *image, >>>>>>> + cmdline_len + DTB_EXTRA_SPACE; >>>>>>> for (;;) { >>>>>>> - buf = vmalloc(buf_size); >>>>>>> + buf = kmalloc(buf_size, GFP_KERNEL); >>>>>> >>>>>> Is there a functional need for this patch? I build the 'dtbs' target just >>>>>> now and sdm845-db845c.dtb is approaching 100K, which feels quite large >>>>>> for kmalloc(). >>>>> >>>>> Changing the allocation from vmalloc() to kmalloc() would help us further >>>>> consolidate the DTB setup code for powerpc and arm64. >>>> >>>> Ok, but at the risk of allocation failure. Can powerpc use vmalloc() >>>> instead? >>> I believe this patch stems from this suggestion by Rob Herring: >>> >>>> This could be taken a step further and do the allocation of the new >>>> FDT. The difference is arm64 uses vmalloc and powerpc uses kmalloc. The >>>> arm64 version also retries with a bigger allocation. That seems >>>> unnecessary. >>> in >>> https://lore.kernel.org/linux-integrity/20201211221006.1052453-3-robh@kernel.org/ >>> The problem is that this patch implements only part of the suggestion, >>> which isn't useful in itself. So the patch series should either drop >>> this patch or consolidate the FDT allocation between the arches. >>> I just tested on powernv and pseries platforms and powerpc can use >>> vmalloc for the FDT buffer. >>> >> >> Thanks for verifying on powerpc platform Thiago. >> >> I'll update the patch to do the following: >> >> => Use vmalloc for FDT buffer allocation on powerpc >> => Keep vmalloc for arm64, but remove the retry on allocation. >> => Also, there was a memory leak of FDT buffer in the error code path on arm64, >> which I'll fix as well. >> >> Did I miss anything? > > Yes, you missed the second part of Rob's suggestion I was mentioning, > which is factoring out the code which allocates the new FDT from both > arm64 and powerpc. >
Sure - I'll address that.
thanks, -lakshmi
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