Re: [PATCH 2/2] arm64/kdump: add code comments for crashkernel reservation cases

2023-01-23 Thread Baoquan He 
On 01/20/23 at 10:02am, Simon Horman wrote:
> On Tue, Jan 17, 2023 at 11:49:21AM +0800, Baoquan He wrote:
> > This will help understand codes on crashkernel reservations on arm64.
> 
> FWIIW, I think you can fold this into the first patch.

Sure, will do.

I folded this into patch 1 at the very beginning. Then felt the added
code comments add lines of change and make the code change not so
straightforward. I admit it's from personal feeling. 

> 
> And, although I have no good idea at this moment, I do wonder
> if the logic can be simplified - I for one really needed the
> comments to understand the retry logic.

Got it. I will consider if I can improve the logic readability. Thanks.

> 
> > Signed-off-by: Baoquan He 
> > ---
> >  arch/arm64/mm/init.c | 13 +
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> > index 26a05af2bfa8..f88ad17cb20d 100644
> > --- a/arch/arm64/mm/init.c
> > +++ b/arch/arm64/mm/init.c
> > @@ -177,6 +177,10 @@ static void __init reserve_crashkernel(void)
> > crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
> >search_base, crash_max);
> > if (!crash_base) {
> > +   /*
> > +* For crashkernel=size[KMG]@offset[KMG], print out failure
> > +* message if can't reserve the specified region.
> > +*/
> > if (fixed_base) {
> > pr_warn("cannot reserve crashkernel region 
> > [0x%llx-0x%llx]\n",
> > search_base, crash_max);
> > @@ -188,6 +192,11 @@ static void __init reserve_crashkernel(void)
> >  * high memory, the minimum required low memory will be
> >  * reserved later.
> >  */
> > +   /*
> > +* For crashkernel=size[KMG], if the first attempt was for
> > +* low memory, fall back to high memory, the minimum required
> > +* low memory will be reserved later.
> > +*/
> 
> I think this duplicates the preceding comment.
> Perhaps just replace the earlier comment with this one.
> 
> > if (!high && crash_max == CRASH_ADDR_LOW_MAX) {
> > crash_max = CRASH_ADDR_HIGH_MAX;
> > search_base = CRASH_ADDR_LOW_MAX;
> > @@ -195,6 +204,10 @@ static void __init reserve_crashkernel(void)
> > goto retry;
> > }
> >  
> > +   /*
> > +* For crashkernel=size[KMG],high, if the first attempt was for
> > +* high memory, fall back to low memory.
> > +*/
> > if (high && (crash_max == CRASH_ADDR_HIGH_MAX)) {
> > crash_max = CRASH_ADDR_LOW_MAX;
> > search_base = 0;
> > -- 
> > 2.34.1
> > 
> > 
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> > 
> 
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Re: [PATCH 2/2] arm64/kdump: add code comments for crashkernel reservation cases

2023-01-20 Thread Simon Horman 
On Tue, Jan 17, 2023 at 11:49:21AM +0800, Baoquan He wrote:
> This will help understand codes on crashkernel reservations on arm64.

FWIIW, I think you can fold this into the first patch.

And, although I have no good idea at this moment, I do wonder
if the logic can be simplified - I for one really needed the
comments to understand the retry logic.

> Signed-off-by: Baoquan He 
> ---
>  arch/arm64/mm/init.c | 13 +
>  1 file changed, 13 insertions(+)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 26a05af2bfa8..f88ad17cb20d 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -177,6 +177,10 @@ static void __init reserve_crashkernel(void)
>   crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
>  search_base, crash_max);
>   if (!crash_base) {
> + /*
> +  * For crashkernel=size[KMG]@offset[KMG], print out failure
> +  * message if can't reserve the specified region.
> +  */
>   if (fixed_base) {
>   pr_warn("cannot reserve crashkernel region 
> [0x%llx-0x%llx]\n",
>   search_base, crash_max);
> @@ -188,6 +192,11 @@ static void __init reserve_crashkernel(void)
>* high memory, the minimum required low memory will be
>* reserved later.
>*/
> + /*
> +  * For crashkernel=size[KMG], if the first attempt was for
> +  * low memory, fall back to high memory, the minimum required
> +  * low memory will be reserved later.
> +  */

I think this duplicates the preceding comment.
Perhaps just replace the earlier comment with this one.

>   if (!high && crash_max == CRASH_ADDR_LOW_MAX) {
>   crash_max = CRASH_ADDR_HIGH_MAX;
>   search_base = CRASH_ADDR_LOW_MAX;
> @@ -195,6 +204,10 @@ static void __init reserve_crashkernel(void)
>   goto retry;
>   }
>  
> + /*
> +  * For crashkernel=size[KMG],high, if the first attempt was for
> +  * high memory, fall back to low memory.
> +  */
>   if (high && (crash_max == CRASH_ADDR_HIGH_MAX)) {
>   crash_max = CRASH_ADDR_LOW_MAX;
>   search_base = 0;
> -- 
> 2.34.1
> 
> 
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[PATCH 2/2] arm64/kdump: add code comments for crashkernel reservation cases

2023-01-16 Thread Baoquan He 
This will help understand codes on crashkernel reservations on arm64.

Signed-off-by: Baoquan He 
---
 arch/arm64/mm/init.c | 13 +
 1 file changed, 13 insertions(+)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 26a05af2bfa8..f88ad17cb20d 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -177,6 +177,10 @@ static void __init reserve_crashkernel(void)
crash_base = memblock_phys_alloc_range(crash_size, CRASH_ALIGN,
   search_base, crash_max);
if (!crash_base) {
+   /*
+* For crashkernel=size[KMG]@offset[KMG], print out failure
+* message if can't reserve the specified region.
+*/
if (fixed_base) {
pr_warn("cannot reserve crashkernel region 
[0x%llx-0x%llx]\n",
search_base, crash_max);
@@ -188,6 +192,11 @@ static void __init reserve_crashkernel(void)
 * high memory, the minimum required low memory will be
 * reserved later.
 */
+   /*
+* For crashkernel=size[KMG], if the first attempt was for
+* low memory, fall back to high memory, the minimum required
+* low memory will be reserved later.
+*/
if (!high && crash_max == CRASH_ADDR_LOW_MAX) {
crash_max = CRASH_ADDR_HIGH_MAX;
search_base = CRASH_ADDR_LOW_MAX;
@@ -195,6 +204,10 @@ static void __init reserve_crashkernel(void)
goto retry;
}
 
+   /*
+* For crashkernel=size[KMG],high, if the first attempt was for
+* high memory, fall back to low memory.
+*/
if (high && (crash_max == CRASH_ADDR_HIGH_MAX)) {
crash_max = CRASH_ADDR_LOW_MAX;
search_base = 0;
-- 
2.34.1


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