On 05/11/22 at 11:20am, Zhen Lei wrote:
> When "crashkernel=X,high" is specified, the specified "crashkernel=Y,low"
> memory is not required in the following corner cases:
> 1. If both CONFIG_ZONE_DMA and CONFIG_ZONE_DMA32 are disabled, it means
> that the devices can access any memory.
> 2. If the system memory is small, the crash high memory may be allocated
> from the DMA zones. If that happens, there's no need to allocate
> another crash low memory because there's already one.
>
> Add condition '(crash_base >= CRASH_ADDR_LOW_MAX)' to determine whether
> the 'high' memory is allocated above DMA zones. Note: when both
> CONFIG_ZONE_DMA and CONFIG_ZONE_DMA32 are disabled, the entire physical
> memory is DMA accessible, CRASH_ADDR_LOW_MAX equals 'PHYS_MASK + 1'.
>
> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
> ---
> Documentation/admin-guide/kernel-parameters.txt | 5 +++--
> arch/arm64/mm/init.c | 3 ++-
> 2 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index f6ff55840751a78..1b543c3109f4851 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -823,7 +823,7 @@
> low memory is needed to make sure DMA buffers for 32-bit
> devices won't run out. Kernel would try to allocate
> at least 256M below 4G automatically.
> - This one let user to specify own low range under 4G
> + This one lets the user specify own low range under 4G
~ This one let users specify own low range ...
Other than this nitpick, LGTM
Acked-by: Baoquan He <bhe@xxxxxxxxxx>
> for second kernel instead.
> 0: to disable low allocation.
> It will be ignored when crashkernel=X,high is not used
> @@ -832,7 +832,8 @@
> [KNL, ARM64] range in low memory.
> This one lets the user specify a low range in the
> DMA zone for the crash dump kernel.
> - It will be ignored when crashkernel=X,high is not used.
> + It will be ignored when crashkernel=X,high is not used
> + or memory reserved is located in the DMA zones.
>
> cryptomgr.notests
> [KNL] Disable crypto self-tests
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 18ba66c90991ea0..ac510fb6a2c0189 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -170,7 +170,8 @@ static void __init reserve_crashkernel(void)
> return;
> }
>
> - if (crash_low_size && reserve_crashkernel_low(crash_low_size)) {
> + if ((crash_base >= CRASH_ADDR_LOW_MAX) &&
> + crash_low_size && reserve_crashkernel_low(crash_low_size)) {
> memblock_phys_free(crash_base, crash_size);
> return;
> }
> --
> 2.25.1
>
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