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Sun, 10 Mar 2019 03:04:56 -0700 (PDT) Received: from localhost ([106.215.118.61]) by smtp.gmail.com with ESMTPSA id r6sm3380076pgp.46.2019.03.10.03.04.55 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 10 Mar 2019 03:04:56 -0700 (PDT) From: Bhupesh Sharma To: linux-kernel@vger.kernel.org Subject: [PATCH v2 1/2] arm64, vmcoreinfo : Append 'PTRS_PER_PGD' to vmcoreinfo Date: Sun, 10 Mar 2019 15:34:01 +0530 Message-Id: <1552212242-9479-2-git-send-email-bhsharma@redhat.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1552212242-9479-1-git-send-email-bhsharma@redhat.com> References: <1552212242-9479-1-git-send-email-bhsharma@redhat.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190310_030457_430222_F829A887 X-CRM114-Status: GOOD ( 13.72 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Kazuhito Hagio , kexec@lists.infradead.org, bhsharma@redhat.com, Will Deacon , James Morse , Dave Anderson , bhupesh.linux@gmail.com, linux-arm-kernel@lists.infradead.org MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP With ARMv8.2-LVA architecture extension availability, arm64 hardware which supports this extension can support a virtual address-space upto 52-bits. Since at the moment we enable the support of this extension in kernel via CONFIG flags, e.g. - User-space 52-bit LVA via CONFIG_ARM64_USER_VA_BITS_52 so, there is no clear mechanism in the user-space right now to determine these CONFIG flag values and hence determine the maximum virtual address space supported by the underlying kernel. User-space tools like 'makedumpfile' therefore are broken currently as they have no proper method to calculate the 'PTRS_PER_PGD' value which is required to perform a page table walk to determine the physical address of a corresponding virtual address found in kcore/vmcoreinfo. If one appends 'PTRS_PER_PGD' number to vmcoreinfo for arm64, it can be used in user-space to determine the maximum virtual address 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-va-support-via-vmcore-upstream-v3/arch/arm64.c#L459 Cc: Mark Rutland Cc: Will Deacon Cc: James Morse Cc: Dave Anderson Cc: Kazuhito Hagio Cc: linux-kernel@vger.kernel.org Cc: kexec@lists.infradead.org Cc: linux-arm-kernel@lists.infradead.org Suggested-by: Steve Capper Signed-off-by: Bhupesh Sharma --- arch/arm64/kernel/crash_core.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/arm64/kernel/crash_core.c b/arch/arm64/kernel/crash_core.c index ca4c3e12d8c5..123a42c56b8e 100644 --- a/arch/arm64/kernel/crash_core.c +++ b/arch/arm64/kernel/crash_core.c @@ -10,6 +10,7 @@ void arch_crash_save_vmcoreinfo(void) { VMCOREINFO_NUMBER(VA_BITS); + VMCOREINFO_NUMBER(PTRS_PER_PGD); /* Please note VMCOREINFO_NUMBER() uses "%d", not "%x" */ vmcoreinfo_append_str("NUMBER(kimage_voffset)=0x%llx\n", kimage_voffset);