[PATCH] arm64, vmcoreinfo : Append 'MAX_USER_VA_BITS' and 'MAX_PHYSMEM_BITS' to vmcoreinfo

Bhupesh Sharma bhsharma at redhat.com
Wed Jan 30 04:23:11 PST 2019


With ARMv8.2-LVA and LPA architecture extensions, arm64 hardware which
supports these extensions can support upto 52-bit virtual and 52-bit
physical addresses respectively.

Since at the moment we enable the support of these extensions via CONFIG
flags, e.g.
 - LPA via CONFIG_ARM64_PA_BITS_52

there are no clear mechanisms in user-space right now to
deteremine these CONFIG flag values and also determine the PARange and
VARange address values.

User-space tools like 'makedumpfile' and 'crash-utility' can instead
use the 'MAX_USER_VA_BITS' and 'MAX_PHYSMEM_BITS' values to determine
the maximum virtual address and physical address (respectively)
supported by underlying kernel.

A reference 'makedumpfile' implementation which uses this approach to
determining the maximum physical address is available in [0].

[0]. https://github.com/bhupesh-sharma/makedumpfile/blob/52-bit-pa-support-via-vmcore-v1/arch/arm64.c#L490

Cc: AKASHI Takahiro <takahiro.akashi at linaro.org>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: Will Deacon <will.deacon at arm.com>
Cc: James Morse <james.morse at arm.com>
Signed-off-by: Bhupesh Sharma <bhsharma at redhat.com>
---
 arch/arm64/kernel/crash_core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/kernel/crash_core.c b/arch/arm64/kernel/crash_core.c
index ca4c3e12d8c5..ad231be5c0d8 100644
--- a/arch/arm64/kernel/crash_core.c
+++ b/arch/arm64/kernel/crash_core.c
@@ -10,6 +10,8 @@
 void arch_crash_save_vmcoreinfo(void)
 {
 	VMCOREINFO_NUMBER(VA_BITS);
+	VMCOREINFO_NUMBER(MAX_USER_VA_BITS);
+	VMCOREINFO_NUMBER(MAX_PHYSMEM_BITS);
 	/* Please note VMCOREINFO_NUMBER() uses "%d", not "%x" */
 	vmcoreinfo_append_str("NUMBER(kimage_voffset)=0x%llx\n",
 						kimage_voffset);
-- 
2.7.4




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