[PATCH v2] x86, calgary: use 8M TCE table size by default

[PATCH v2] x86, calgary: use 8M TCE table size by default

[WANG Chao]

New kexec-tools wants to pass kdump kernel needed memmap via E820
directly, instead of memmap=exactmap. This makes saved_max_pfn not
be passed down to 2nd kernel. To keep 1st kernel and 2nd kernel using
the same TCE table size, Muli suggest to hard code the size to max (8M).

We can't get rid of saved_max_pfn this time, for backward compatibility
with old first kernel and new second kernel. However new first kernel
and old second kernel can not work unfortunately.

v2->v1:
- retain saved_max_pfn so new 2nd kernel can work with old 1st kernel
  from Vivek

Signed-off-by: WANG Chao <chaowang@redhat.com>
---
 arch/x86/kernel/pci-calgary_64.c | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/pci-calgary_64.c b/arch/x86/kernel/pci-calgary_64.c
index 299d493..0497f71 100644
--- a/arch/x86/kernel/pci-calgary_64.c
+++ b/arch/x86/kernel/pci-calgary_64.c
@@ -1207,23 +1207,31 @@ error:
 	return ret;
 }
 
-static inline int __init determine_tce_table_size(u64 ram)
+static inline int __init determine_tce_table_size(void)
 {
 	int ret;
 
 	if (specified_table_size != TCE_TABLE_SIZE_UNSPECIFIED)
 		return specified_table_size;
 
-	/*
-	 * Table sizes are from 0 to 7 (TCE_TABLE_SIZE_64K to
-	 * TCE_TABLE_SIZE_8M). Table size 0 has 8K entries and each
-	 * larger table size has twice as many entries, so shift the
-	 * max ram address by 13 to divide by 8K and then look at the
-	 * order of the result to choose between 0-7.
-	 */
-	ret = get_order(ram >> 13);
-	if (ret > TCE_TABLE_SIZE_8M)
+	if (is_kdump_kernel() && saved_max_pfn) {
+		/*
+		 * Table sizes are from 0 to 7 (TCE_TABLE_SIZE_64K to
+		 * TCE_TABLE_SIZE_8M). Table size 0 has 8K entries and each
+		 * larger table size has twice as many entries, so shift the
+		 * max ram address by 13 to divide by 8K and then look at the
+		 * order of the result to choose between 0-7.
+		 */
+		ret = get_order((saved_max_pfn * PAGE_SIZE) >> 13);
+		if (ret > TCE_TABLE_SIZE_8M)
+			ret = TCE_TABLE_SIZE_8M;
+	} else {
+		/*
+		 * Use 8M by default (suggested by Muli) if it's not
+		 * kdump kernel and saved_max_pfn isn't set.
+		 */
 		ret = TCE_TABLE_SIZE_8M;
+	}
 
 	return ret;
 }
@@ -1418,8 +1426,7 @@ int __init detect_calgary(void)
 		return -ENOMEM;
 	}
 
-	specified_table_size = determine_tce_table_size((is_kdump_kernel() ?
-					saved_max_pfn : max_pfn) * PAGE_SIZE);
+	specified_table_size = determine_tce_table_size();
 
 	for (bus = 0; bus < MAX_PHB_BUS_NUM; bus++) {
 		struct calgary_bus_info *info = &bus_info[bus];
-- 
1.8.5.3


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Re: [PATCH v2] x86, calgary: use 8M TCE table size by default

[Vivek Goyal]

On Mon, Mar 10, 2014 at 10:52:00PM +0800, WANG Chao wrote:
> New kexec-tools wants to pass kdump kernel needed memmap via E820
> directly, instead of memmap=exactmap. This makes saved_max_pfn not
> be passed down to 2nd kernel. To keep 1st kernel and 2nd kernel using
> the same TCE table size, Muli suggest to hard code the size to max (8M).
> 
> We can't get rid of saved_max_pfn this time, for backward compatibility
> with old first kernel and new second kernel. However new first kernel
> and old second kernel can not work unfortunately.
> 
> v2->v1:
> - retain saved_max_pfn so new 2nd kernel can work with old 1st kernel
>   from Vivek
> 
> Signed-off-by: WANG Chao <chaowang@redhat.com>

This patch looks good to me. This will use saved_max_pfn to determine
table size and retain backward compatibility with old kernel (if user
uses right kexec cmdline option --pass-memmap).

For others (majority of the cases), both first kernel and second kernel
will use 8M of calgary table. 8M does sound a lot in terms of memory but
assumption here is that there might be only some machines with calgary
hardware and only these will pay the penalty of this increased memory 
usage. This sounds better than exporting table size to user space.

Acked-by: Vivek Goyal <vgoyal@redhat.com>

Thanks
Vivek

> ---
>  arch/x86/kernel/pci-calgary_64.c | 31 +++++++++++++++++++------------
>  1 file changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kernel/pci-calgary_64.c b/arch/x86/kernel/pci-calgary_64.c
> index 299d493..0497f71 100644
> --- a/arch/x86/kernel/pci-calgary_64.c
> +++ b/arch/x86/kernel/pci-calgary_64.c
> @@ -1207,23 +1207,31 @@ error:
>  	return ret;
>  }
>  
> -static inline int __init determine_tce_table_size(u64 ram)
> +static inline int __init determine_tce_table_size(void)
>  {
>  	int ret;
>  
>  	if (specified_table_size != TCE_TABLE_SIZE_UNSPECIFIED)
>  		return specified_table_size;
>  
> -	/*
> -	 * Table sizes are from 0 to 7 (TCE_TABLE_SIZE_64K to
> -	 * TCE_TABLE_SIZE_8M). Table size 0 has 8K entries and each
> -	 * larger table size has twice as many entries, so shift the
> -	 * max ram address by 13 to divide by 8K and then look at the
> -	 * order of the result to choose between 0-7.
> -	 */
> -	ret = get_order(ram >> 13);
> -	if (ret > TCE_TABLE_SIZE_8M)
> +	if (is_kdump_kernel() && saved_max_pfn) {
> +		/*
> +		 * Table sizes are from 0 to 7 (TCE_TABLE_SIZE_64K to
> +		 * TCE_TABLE_SIZE_8M). Table size 0 has 8K entries and each
> +		 * larger table size has twice as many entries, so shift the
> +		 * max ram address by 13 to divide by 8K and then look at the
> +		 * order of the result to choose between 0-7.
> +		 */
> +		ret = get_order((saved_max_pfn * PAGE_SIZE) >> 13);
> +		if (ret > TCE_TABLE_SIZE_8M)
> +			ret = TCE_TABLE_SIZE_8M;
> +	} else {
> +		/*
> +		 * Use 8M by default (suggested by Muli) if it's not
> +		 * kdump kernel and saved_max_pfn isn't set.
> +		 */
>  		ret = TCE_TABLE_SIZE_8M;
> +	}
>  
>  	return ret;
>  }
> @@ -1418,8 +1426,7 @@ int __init detect_calgary(void)
>  		return -ENOMEM;
>  	}
>  
> -	specified_table_size = determine_tce_table_size((is_kdump_kernel() ?
> -					saved_max_pfn : max_pfn) * PAGE_SIZE);
> +	specified_table_size = determine_tce_table_size();
>  
>  	for (bus = 0; bus < MAX_PHB_BUS_NUM; bus++) {
>  		struct calgary_bus_info *info = &bus_info[bus];
> -- 
> 1.8.5.3

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Re: [PATCH v2] x86, calgary: use 8M TCE table size by default

[Muli Ben-Yehuda]

Patch looks good to me.

Acked-by: Muli Ben-Yehuda <mulix@mulix.org>

Cheers,
Muli

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Re: [PATCH v2] x86, calgary: use 8M TCE table size by default

[Jon Mason]

On Mon, Mar 10, 2014 at 8:54 AM, Muli Ben-Yehuda <muli@cs.technion.ac.il> wrote:
> Patch looks good to me.
>
> Acked-by: Muli Ben-Yehuda <mulix@mulix.org>

Me too (just in case you want us both).

Acked-by: Jon Mason <jdmason@kudzu.us>

>
> Cheers,
> Muli

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Re: [PATCH v2] x86, calgary: use 8M TCE table size by default

[WANG Chao]

On 03/10/14 at 10:26pm, Jon Mason wrote:
> On Mon, Mar 10, 2014 at 8:54 AM, Muli Ben-Yehuda <muli@cs.technion.ac.il> wrote:
> > Patch looks good to me.
> >
> > Acked-by: Muli Ben-Yehuda <mulix@mulix.org>
> 
> Me too (just in case you want us both).
> 
> Acked-by: Jon Mason <jdmason@kudzu.us>

Thanks for review and helping push this change, to all of you.

WANG Chao

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Re: [PATCH v2] x86, calgary: use 8M TCE table size by default

[Vivek Goyal]

Hi hpa,

I am wondering how to make progress on calgary issue now. We do want to
cleanup kexec-tools code and move to passing memory ranges in bootparams.

I see two choices here.

- Take this patch in so that new kernel code will work with modified
  kexec-tools without any user intervention. (Both first and second kernel
  need to be new). 

- Don't take this patch in and calgary will be broken with new
  kexec-tools. And that will always require manual user intervention
  from user to force passing memmap on command line.

I kind of prefer the first option so that even if there are some calgary
machines out there, they will work automatically with new kernel and
will require manual intervention only for old kernels and new kexec-tool
cobination.

But I can live with second option too if that's everybody agrees to and
hopefully we don't get lots of reports of breaking kdump with kexec-tools
upgrade.

Thanks
Vivek

On Mon, Mar 10, 2014 at 10:52:00PM +0800, WANG Chao wrote:
> New kexec-tools wants to pass kdump kernel needed memmap via E820
> directly, instead of memmap=exactmap. This makes saved_max_pfn not
> be passed down to 2nd kernel. To keep 1st kernel and 2nd kernel using
> the same TCE table size, Muli suggest to hard code the size to max (8M).
> 
> We can't get rid of saved_max_pfn this time, for backward compatibility
> with old first kernel and new second kernel. However new first kernel
> and old second kernel can not work unfortunately.
> 
> v2->v1:
> - retain saved_max_pfn so new 2nd kernel can work with old 1st kernel
>   from Vivek
> 
> Signed-off-by: WANG Chao <chaowang@redhat.com>
> ---
>  arch/x86/kernel/pci-calgary_64.c | 31 +++++++++++++++++++------------
>  1 file changed, 19 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kernel/pci-calgary_64.c b/arch/x86/kernel/pci-calgary_64.c
> index 299d493..0497f71 100644
> --- a/arch/x86/kernel/pci-calgary_64.c
> +++ b/arch/x86/kernel/pci-calgary_64.c
> @@ -1207,23 +1207,31 @@ error:
>  	return ret;
>  }
>  
> -static inline int __init determine_tce_table_size(u64 ram)
> +static inline int __init determine_tce_table_size(void)
>  {
>  	int ret;
>  
>  	if (specified_table_size != TCE_TABLE_SIZE_UNSPECIFIED)
>  		return specified_table_size;
>  
> -	/*
> -	 * Table sizes are from 0 to 7 (TCE_TABLE_SIZE_64K to
> -	 * TCE_TABLE_SIZE_8M). Table size 0 has 8K entries and each
> -	 * larger table size has twice as many entries, so shift the
> -	 * max ram address by 13 to divide by 8K and then look at the
> -	 * order of the result to choose between 0-7.
> -	 */
> -	ret = get_order(ram >> 13);
> -	if (ret > TCE_TABLE_SIZE_8M)
> +	if (is_kdump_kernel() && saved_max_pfn) {
> +		/*
> +		 * Table sizes are from 0 to 7 (TCE_TABLE_SIZE_64K to
> +		 * TCE_TABLE_SIZE_8M). Table size 0 has 8K entries and each
> +		 * larger table size has twice as many entries, so shift the
> +		 * max ram address by 13 to divide by 8K and then look at the
> +		 * order of the result to choose between 0-7.
> +		 */
> +		ret = get_order((saved_max_pfn * PAGE_SIZE) >> 13);
> +		if (ret > TCE_TABLE_SIZE_8M)
> +			ret = TCE_TABLE_SIZE_8M;
> +	} else {
> +		/*
> +		 * Use 8M by default (suggested by Muli) if it's not
> +		 * kdump kernel and saved_max_pfn isn't set.
> +		 */
>  		ret = TCE_TABLE_SIZE_8M;
> +	}
>  
>  	return ret;
>  }
> @@ -1418,8 +1426,7 @@ int __init detect_calgary(void)
>  		return -ENOMEM;
>  	}
>  
> -	specified_table_size = determine_tce_table_size((is_kdump_kernel() ?
> -					saved_max_pfn : max_pfn) * PAGE_SIZE);
> +	specified_table_size = determine_tce_table_size();
>  
>  	for (bus = 0; bus < MAX_PHB_BUS_NUM; bus++) {
>  		struct calgary_bus_info *info = &bus_info[bus];
> -- 
> 1.8.5.3

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Re: [PATCH v2] x86, calgary: use 8M TCE table size by default

[H. Peter Anvin]

On 03/20/2014 08:54 AM, Vivek Goyal wrote:
> Hi hpa,
> 
> I am wondering how to make progress on calgary issue now. We do want to
> cleanup kexec-tools code and move to passing memory ranges in bootparams.
> 
> I see two choices here.
> 
> - Take this patch in so that new kernel code will work with modified
>   kexec-tools without any user intervention. (Both first and second kernel
>   need to be new). 
> 
> - Don't take this patch in and calgary will be broken with new
>   kexec-tools. And that will always require manual user intervention
>   from user to force passing memmap on command line.
> 
> I kind of prefer the first option so that even if there are some calgary
> machines out there, they will work automatically with new kernel and
> will require manual intervention only for old kernels and new kexec-tool
> cobination.
> 
> But I can live with second option too if that's everybody agrees to and
> hopefully we don't get lots of reports of breaking kdump with kexec-tools
> upgrade.
> 

The patch seems simple enough and doesn't require any new command line
hacks.  It has been widely reviewed and acked, so I'll pick it up.

	-hpa



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