[PATCH] makedumpfile/arm64: Add support for ARMv8.2-LVA (52-bit user-space VA support)

Kazuhito Hagio k-hagio at ab.jp.nec.com
Mon Feb 11 14:03:50 PST 2019


Hi Bhupesh,

On 2/7/2019 2:52 PM, Bhupesh Sharma wrote:
> With ARMv8.2-LVA architecture extension availability, arm64 hardware
> which supports this extension can support upto 52-bit virtual
> addresses. It is specially useful for having a 52-bit user-space virtual
> address space while the kernel can still retain 48-bit virtual
> addresses.
> 
> Since at the moment we enable the support of this extensions in the
> kernel via a CONFIG flags (CONFIG_ARM64_USER_VA_BITS_52), so there are
> no clear mechanisms in user-space to determine this CONFIG
> flag value and use it to determine the PA address range values.
> 
> 'makedumpfile' can instead use 'MAX_USER_VA_BITS' value to
> determine the maximum virtual physical address supported by user-space.
> If 'MAX_USER_VA_BITS' value is greater than 'VA_BITS' than we might be
> running a use-case where user-space is 52-bit and underlying kernel is
> still 48-bit. The increased 'PTRS_PER_PGD' value for such cases can then
> be calculated as is done by the underlying kernel (see kernel file
> 'arch/arm64/include/asm/pgtable-hwdef.h' for details):

Thank you for the patch.
I can't test the config yet, but this looks necessary.

> 
> I have sent a kernel patch upstream to add 'MAX_USER_VA_BITS' to
> vmcoreinfo for arm64 (see [0]).
> 
> This patch is in accordance with ARMv8 Architecture Reference Manual
> version D.a
> 
> [0].
> http://lists.infradead.org/pipermail/kexec/2019-February/022411.html
> 
> Signed-off-by: Bhupesh Sharma <bhsharma at redhat.com>
> ---
>  arch/arm64.c   | 105 +++++++++++++++++++++++++++++++++++++++++----------------
>  makedumpfile.c |   2 ++
>  makedumpfile.h |   1 +
>  3 files changed, 79 insertions(+), 29 deletions(-)
> 
> diff --git a/arch/arm64.c b/arch/arm64.c
> index a1db7dc63107..b522e93f4e80 100644
> --- a/arch/arm64.c
> +++ b/arch/arm64.c
> @@ -47,6 +47,7 @@ typedef struct {
>  static int lpa_52_bit_support_available;
>  static int pgtable_level;
>  static int va_bits;
> +static int max_user_va_bits;
>  static unsigned long kimage_voffset;
> 
>  #define SZ_4K			4096
> @@ -145,7 +146,7 @@ get_page_table_level_arm64(void)
>  #define PGDIR_SHIFT		ARM64_HW_PGTABLE_LEVEL_SHIFT(4 - (get_page_table_level_arm64()))
>  #define PGDIR_SIZE		(_AC(1, UL) << PGDIR_SHIFT)
>  #define PGDIR_MASK		(~(PGDIR_SIZE-1))
> -#define PTRS_PER_PGD		(1 << ((va_bits) - PGDIR_SHIFT))
> +#define PTRS_PER_PGD		(1 << ((max_user_va_bits) - PGDIR_SHIFT))
> 
>  /*
>   * Section address mask and size definitions.
> @@ -478,6 +479,46 @@ get_stext_symbol(void)
>  	return(found ? kallsym : FALSE);
>  }
> 
> +static int
> +get_va_bits_from_stext_arm64(void)
> +{
> +	ulong _stext;
> +
> +	_stext = get_stext_symbol();
> +	if (!_stext) {
> +		ERRMSG("Can't get the symbol of _stext.\n");
> +		return FALSE;
> +	}
> +
> +	/* Derive va_bits as per arch/arm64/Kconfig */
> +	if ((_stext & PAGE_OFFSET_36) == PAGE_OFFSET_36) {
> +		va_bits = 36;
> +	} else if ((_stext & PAGE_OFFSET_39) == PAGE_OFFSET_39) {
> +		va_bits = 39;
> +	} else if ((_stext & PAGE_OFFSET_42) == PAGE_OFFSET_42) {
> +		va_bits = 42;
> +	} else if ((_stext & PAGE_OFFSET_47) == PAGE_OFFSET_47) {
> +		va_bits = 47;
> +	} else if ((_stext & PAGE_OFFSET_48) == PAGE_OFFSET_48) {
> +		va_bits = 48;
> +	} else {
> +		ERRMSG("Cannot find a proper _stext for calculating VA_BITS\n");
> +		return FALSE;
> +	}
> +
> +	DEBUG_MSG("va_bits      : %d\n", va_bits);

Please add "(_stext)" to the end of line for debugging.

> +
> +	return TRUE;
> +}
> +
> +static void
> +get_page_offset_arm64(void)
> +{
> +	info->page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
> +
> +	DEBUG_MSG("page_offset  : %lx\n", info->page_offset);
> +}
> +
>  int
>  get_machdep_info_arm64(void)
>  {
> @@ -493,8 +534,37 @@ get_machdep_info_arm64(void)
>  	/* Check if va_bits is still not initialized. If still 0, call
>  	 * get_versiondep_info() to initialize the same.
>  	 */
> +	if (NUMBER(VA_BITS) != NOT_FOUND_NUMBER) {
> +		va_bits = NUMBER(VA_BITS);
> +		DEBUG_MSG("va_bits    : %d (vmcoreinfo)\n",
> +				va_bits);
> +	}
> +
> +	/* Check if va_bits is still not initialized. If still 0, call
> +	 * get_versiondep_info() to initialize the same from _stext
> +	 * symbol.
> +	 */
>  	if (!va_bits)
> -		get_versiondep_info_arm64();
> +		if (get_va_bits_from_stext_arm64() == ERROR)
> +			return ERROR;

These ERRORs should be FALSE.

> +
> +	get_page_offset_arm64();
> +
> +	if (NUMBER(MAX_USER_VA_BITS) != NOT_FOUND_NUMBER) {
> +		max_user_va_bits = NUMBER(MAX_USER_VA_BITS);
> +		DEBUG_MSG("max_user_va_bits : %d (vmcoreinfo)\n",
> +				max_user_va_bits);
> +	}
> +
> +	/* Check if max_user_va_bits is still not initialized.
> +	 * If still 0, its not available in vmcoreinfo and its
> +	 * safe to initialize it with va_bits.
> +	 */
> +	if (!max_user_va_bits) {
> +		max_user_va_bits = va_bits;
> +		DEBUG_MSG("max_user_va_bits : %d (default = va_bits)\n",
> +				max_user_va_bits);
> +	}
> 
>  	if (!calculate_plat_config()) {
>  		ERRMSG("Can't determine platform config values\n");
> @@ -533,34 +603,11 @@ get_xen_info_arm64(void)
>  int
>  get_versiondep_info_arm64(void)
>  {
> -	ulong _stext;
> -
> -	_stext = get_stext_symbol();
> -	if (!_stext) {
> -		ERRMSG("Can't get the symbol of _stext.\n");
> -		return FALSE;
> -	}
> -
> -	/* Derive va_bits as per arch/arm64/Kconfig */
> -	if ((_stext & PAGE_OFFSET_36) == PAGE_OFFSET_36) {
> -		va_bits = 36;
> -	} else if ((_stext & PAGE_OFFSET_39) == PAGE_OFFSET_39) {
> -		va_bits = 39;
> -	} else if ((_stext & PAGE_OFFSET_42) == PAGE_OFFSET_42) {
> -		va_bits = 42;
> -	} else if ((_stext & PAGE_OFFSET_47) == PAGE_OFFSET_47) {
> -		va_bits = 47;
> -	} else if ((_stext & PAGE_OFFSET_48) == PAGE_OFFSET_48) {
> -		va_bits = 48;
> -	} else {
> -		ERRMSG("Cannot find a proper _stext for calculating VA_BITS\n");
> -		return FALSE;
> -	}
> -
> -	info->page_offset = (0xffffffffffffffffUL) << (va_bits - 1);
> +	if (!va_bits)
> +		if (get_va_bits_from_stext_arm64() == ERROR)
> +			return ERROR;

Same as above.

And, it would be helpful if you would rebase this after fixing the
52-bit PA patch.

Thanks,
Kazu

> 
> -	DEBUG_MSG("va_bits      : %d\n", va_bits);
> -	DEBUG_MSG("page_offset  : %lx\n", info->page_offset);
> +	get_page_offset_arm64();
> 
>  	return TRUE;
>  }
> diff --git a/makedumpfile.c b/makedumpfile.c
> index b7c1c01251bf..ccf7eb4408ba 100644
> --- a/makedumpfile.c
> +++ b/makedumpfile.c
> @@ -2291,6 +2291,7 @@ write_vmcoreinfo_data(void)
> 
>  	WRITE_NUMBER("HUGETLB_PAGE_DTOR", HUGETLB_PAGE_DTOR);
>  #ifdef __aarch64__
> +	WRITE_NUMBER("MAX_USER_VA_BITS", MAX_USER_VA_BITS);
>  	WRITE_NUMBER("VA_BITS", VA_BITS);
>  	WRITE_NUMBER_UNSIGNED("PHYS_OFFSET", PHYS_OFFSET);
>  	WRITE_NUMBER_UNSIGNED("kimage_voffset", kimage_voffset);
> @@ -2694,6 +2695,7 @@ read_vmcoreinfo(void)
>  	READ_NUMBER("PAGE_BUDDY_MAPCOUNT_VALUE", PAGE_BUDDY_MAPCOUNT_VALUE);
>  	READ_NUMBER("phys_base", phys_base);
>  #ifdef __aarch64__
> +	READ_NUMBER("MAX_USER_VA_BITS", MAX_USER_VA_BITS);
>  	READ_NUMBER("VA_BITS", VA_BITS);
>  	READ_NUMBER_UNSIGNED("PHYS_OFFSET", PHYS_OFFSET);
>  	READ_NUMBER_UNSIGNED("kimage_voffset", kimage_voffset);
> diff --git a/makedumpfile.h b/makedumpfile.h
> index d49f1f1fc1a9..3fa810e0bb40 100644
> --- a/makedumpfile.h
> +++ b/makedumpfile.h
> @@ -1933,6 +1933,7 @@ struct number_table {
>  	long    HUGETLB_PAGE_DTOR;
>  	long	phys_base;
>  #ifdef __aarch64__
> +	long 	MAX_USER_VA_BITS;
>  	long 	VA_BITS;
>  	unsigned long	PHYS_OFFSET;
>  	unsigned long	kimage_voffset;
> --
> 2.7.4
> 





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