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 20:00:34 -0800 |
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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?
thanks, -lakshmi
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