APPLIED: [SRU][Focal][PATCH] arm64/crash_core: Export TCR_EL1.T1SZ in vmcoreinfo

[Stefan Bader]

On 15.04.21 14:10, Ioanna Alifieraki wrote:
> From: Bhupesh Sharma <bhsharma at redhat.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1919275
> 
> TCR_EL1.TxSZ, which controls the VA space size, is configured by a
> single kernel image to support either 48-bit or 52-bit VA space.
> 
> If the ARMv8.2-LVA optional feature is present and we are running
> with a 64KB page size, then it is possible to use 52-bits of address
> space for both userspace and kernel addresses. However, any kernel
> binary that supports 52-bit must also be able to fall back to 48-bit
> at early boot time if the hardware feature is not present.
> 
> Since TCR_EL1.T1SZ indicates the size of the memory region addressed by
> TTBR1_EL1, export the same in vmcoreinfo. User-space utilities like
> makedumpfile and crash-utility need to read this value from vmcoreinfo
> for determining if a virtual address lies in the linear map range.
> 
> While at it also add documentation for TCR_EL1.T1SZ variable being
> added to vmcoreinfo.
> 
> It indicates the size offset of the memory region addressed by
> TTBR1_EL1.
> 
> Signed-off-by: Bhupesh Sharma <bhsharma at redhat.com>
> Tested-by: John Donnelly <john.p.donnelly at oracle.com>
> Tested-by: Kamlakant Patel <kamlakantp at marvell.com>
> Tested-by: Amit Daniel Kachhap <amit.kachhap at arm.com>
> Reviewed-by: James Morse <james.morse at arm.com>
> Reviewed-by: Amit Daniel Kachhap <amit.kachhap at arm.com>
> Cc: James Morse <james.morse at arm.com>
> Cc: Mark Rutland <mark.rutland at arm.com>
> Cc: Will Deacon <will at kernel.org>
> Cc: Steve Capper <steve.capper at arm.com>
> Cc: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> Cc: Dave Anderson <anderson at redhat.com>
> Cc: Kazuhito Hagio <k-hagio at ab.jp.nec.com>
> Cc: linux-arm-kernel at lists.infradead.org
> Cc: linux-kernel at vger.kernel.org
> Cc: kexec at lists.infradead.org
> Link: https://lore.kernel.org/r/1589395957-24628-3-git-send-email-bhsharma@redhat.com
> [catalin.marinas at arm.com: removed vabits_actual from the commit log]
> Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
> (backported from commit bbdbc11804ff0b4130e7550113b452e96a74d16e)
> [hook 1: resolve conflict in documentation]
> Signed-off-by: Ioanna Alifieraki <ioanna-maria.alifieraki at canonical.com>
> ---
>   Documentation/admin-guide/kdump/vmcoreinfo.rst | 11 +++++++++++
>   arch/arm64/include/asm/pgtable-hwdef.h         |  1 +
>   arch/arm64/kernel/crash_core.c                 | 10 ++++++++++
>   3 files changed, 22 insertions(+)
> 
> diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst
> index 007a6b86e0ee..ba1aed57e55d 100644
> --- a/Documentation/admin-guide/kdump/vmcoreinfo.rst
> +++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst
> @@ -393,6 +393,17 @@ KERNELOFFSET
>   The kernel randomization offset. Used to compute the page offset. If
>   KASLR is disabled, this value is zero.
>   
> +TCR_EL1.T1SZ
> +------------
> +
> +Indicates the size offset of the memory region addressed by TTBR1_EL1.
> +The region size is 2^(64-T1SZ) bytes.
> +
> +TTBR1_EL1 is the table base address register specified by ARMv8-A
> +architecture which is used to lookup the page-tables for the Virtual
> +addresses in the higher VA range (refer to ARMv8 ARM document for
> +more details).
> +
>   arm
>   ===
>   
> diff --git a/arch/arm64/include/asm/pgtable-hwdef.h b/arch/arm64/include/asm/pgtable-hwdef.h
> index 3df60f97da1f..a0f789fa25f3 100644
> --- a/arch/arm64/include/asm/pgtable-hwdef.h
> +++ b/arch/arm64/include/asm/pgtable-hwdef.h
> @@ -215,6 +215,7 @@
>   #define TCR_TxSZ(x)		(TCR_T0SZ(x) | TCR_T1SZ(x))
>   #define TCR_TxSZ_WIDTH		6
>   #define TCR_T0SZ_MASK		(((UL(1) << TCR_TxSZ_WIDTH) - 1) << TCR_T0SZ_OFFSET)
> +#define TCR_T1SZ_MASK		(((UL(1) << TCR_TxSZ_WIDTH) - 1) << TCR_T1SZ_OFFSET)
>   
>   #define TCR_EPD0_SHIFT		7
>   #define TCR_EPD0_MASK		(UL(1) << TCR_EPD0_SHIFT)
> diff --git a/arch/arm64/kernel/crash_core.c b/arch/arm64/kernel/crash_core.c
> index ca4c3e12d8c5..ec8095bfe23e 100644
> --- a/arch/arm64/kernel/crash_core.c
> +++ b/arch/arm64/kernel/crash_core.c
> @@ -6,6 +6,14 @@
>   
>   #include <linux/crash_core.h>
>   #include <asm/memory.h>
> +#include <asm/pgtable-hwdef.h>
> +
> +static inline u64 get_tcr_el1_t1sz(void);
> +
> +static inline u64 get_tcr_el1_t1sz(void)
> +{
> +	return (read_sysreg(tcr_el1) & TCR_T1SZ_MASK) >> TCR_T1SZ_OFFSET;
> +}
>   
>   void arch_crash_save_vmcoreinfo(void)
>   {
> @@ -15,5 +23,7 @@ void arch_crash_save_vmcoreinfo(void)
>   						kimage_voffset);
>   	vmcoreinfo_append_str("NUMBER(PHYS_OFFSET)=0x%llx\n",
>   						PHYS_OFFSET);
> +	vmcoreinfo_append_str("NUMBER(TCR_EL1_T1SZ)=0x%llx\n",
> +						get_tcr_el1_t1sz());
>   	vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset());
>   }
> 
Applied to focal:linux/master-next. Thanks.

-Stefan


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