Hi Kalesh, On Thu, Jul 21, 2022 at 6:57 AM Kalesh Singh <kaleshsingh@xxxxxxxxxx> wrote: > > Hi all, > > This is v5 of nVHE hypervisor stacktraces support. The series is based on > arm64 for-next/stacktrace. > > The previous versions were posted at: > v4: https://lore.kernel.org/r/20220715061027.1612149-1-kaleshsingh@xxxxxxxxxx/ > v3: https://lore.kernel.org/r/20220607165105.639716-1-kaleshsingh@xxxxxxxxxx/ > v2: https://lore.kernel.org/r/20220502191222.4192768-1-kaleshsingh@xxxxxxxxxx/ > v1: https://lore.kernel.org/r/20220427184716.1949239-1-kaleshsingh@xxxxxxxxxx/ > > The main updates in this version are some refactoring to move stuff out of > stacktrace/nvhe.h (leaving only the unwinder implementation in the header); > and fixing the symbolization of the hyp stacktrace when KASLR is enabled; > along with the addressing the other minor comments. > > Patch 18 (KVM: arm64: Dump nVHE hypervisor stack on panic) was also squashed > into earlier patches. > > The previous cover letter is copied below for convenience. > > Thanks all for your feedback. Thank you for this. This will be very helpful. For the whole series: Tested-by: Fuad Tabba <tabba@xxxxxxxxxx> Cheers, /fuad > > --Kalesh > > ============ > > KVM nVHE Stack unwinding. > === > > nVHE has two modes of operation: protected (pKVM) and unprotected > (conventional nVHE). Depending on the mode, a slightly different approach > is used to dump the hypervisor stacktrace but the core unwinding logic > remains the same. > > Protected nVHE (pKVM) stacktraces > ==== > > In protected nVHE mode, the host cannot directly access hypervisor memory. > > The hypervisor stack unwinding happens in EL2 and is made accessible to > the host via a shared buffer. Symbolizing and printing the stacktrace > addresses is delegated to the host and happens in EL1. > > Non-protected (Conventional) nVHE stacktraces > ==== > > In non-protected mode, the host is able to directly access the hypervisor > stack pages. > > The hypervisor stack unwinding and dumping of the stacktrace is performed > by the host in EL1, as this avoids the memory overhead of setting up > shared buffers between the host and hypervisor. > > Resuing the Core Unwinding Logic > ==== > > Since the hypervisor cannot link against the kernel code in proteced mode. > The common stack unwinding code is moved to a shared header to allow reuse > in the nVHE hypervisor. > > Reducing the memory footprint > ==== > > In this version the below steps were taken to reduce the memory usage of > nVHE stack unwinding: > > 1) The nVHE overflow stack is reduced from PAGE_SIZE to 4KB; benificial > for configurations with non 4KB pages (16KB or 64KB pages). > 2) In protected nVHE mode (pKVM), the shared stacktrace buffers with the > host are reduced from PAGE_SIZE to the minimum size required. > 3) In systems other than Android, conventional nVHE makes up the vast > majority of use case. So the pKVM stack tracing is disabled by default > (!CONFIG_PROTECTED_NVHE_STACKTRACE), which avoid the memory usage for > setting up shared buffers. > 4) In non-protected nVHE mode (conventional nVHE), the stack unwinding > is done directly in EL1 by the host and no shared buffers with the > hypervisor are needed. > > Sample Output > ==== > > The below shows an example output from a simple stack overflow test: > > [ 126.862960] kvm [371]: nVHE hyp panic at: [<ffff8000090a51d0>] __kvm_nvhe_recursive_death+0x10/0x34! > [ 126.869920] kvm [371]: Protected nVHE HYP call trace: > [ 126.870528] kvm [371]: [<ffff8000090a5570>] __kvm_nvhe_hyp_panic+0xac/0xf8 > [ 126.871342] kvm [371]: [<ffff8000090a55cc>] __kvm_nvhe_hyp_panic_bad_stack+0x10/0x10 > [ 126.872174] kvm [371]: [<ffff8000090a51e4>] __kvm_nvhe_recursive_death+0x24/0x34 > [ 126.872971] kvm [371]: [<ffff8000090a51e4>] __kvm_nvhe_recursive_death+0x24/0x34 > . . . > > [ 126.927314] kvm [371]: [<ffff8000090a51e4>] __kvm_nvhe_recursive_death+0x24/0x34 > [ 126.927727] kvm [371]: [<ffff8000090a51e4>] __kvm_nvhe_recursive_death+0x24/0x34 > [ 126.928137] kvm [371]: [<ffff8000090a4de4>] __kvm_nvhe___kvm_vcpu_run+0x30/0x40c > [ 126.928561] kvm [371]: [<ffff8000090a7b64>] __kvm_nvhe_handle___kvm_vcpu_run+0x30/0x48 > [ 126.928984] kvm [371]: [<ffff8000090a78b8>] __kvm_nvhe_handle_trap+0xc4/0x128 > [ 126.929385] kvm [371]: [<ffff8000090a6864>] __kvm_nvhe___host_exit+0x64/0x64 > [ 126.929804] kvm [371]: ---- End of Protected nVHE HYP call trace ---- > > ============ > > Kalesh Singh (17): > arm64: stacktrace: Add shared header for common stack unwinding code > arm64: stacktrace: Factor out on_accessible_stack_common() > arm64: stacktrace: Factor out unwind_next_common() > arm64: stacktrace: Handle frame pointer from different address spaces > arm64: stacktrace: Factor out common unwind() > arm64: stacktrace: Add description of stacktrace/common.h > KVM: arm64: On stack overflow switch to hyp overflow_stack > KVM: arm64: Add PROTECTED_NVHE_STACKTRACE Kconfig > KVM: arm64: Allocate shared pKVM hyp stacktrace buffers > KVM: arm64: Stub implementation of pKVM HYP stack unwinder > KVM: arm64: Stub implementation of non-protected nVHE HYP stack > unwinder > KVM: arm64: Save protected-nVHE (pKVM) hyp stacktrace > KVM: arm64: Prepare non-protected nVHE hypervisor stacktrace > KVM: arm64: Implement protected nVHE hyp stack unwinder > KVM: arm64: Implement non-protected nVHE hyp stack unwinder > KVM: arm64: Introduce pkvm_dump_backtrace() > KVM: arm64: Introduce hyp_dump_backtrace() > > arch/arm64/include/asm/kvm_asm.h | 16 ++ > arch/arm64/include/asm/memory.h | 8 + > arch/arm64/include/asm/stacktrace.h | 92 +++++---- > arch/arm64/include/asm/stacktrace/common.h | 230 +++++++++++++++++++++ > arch/arm64/include/asm/stacktrace/nvhe.h | 199 ++++++++++++++++++ > arch/arm64/kernel/stacktrace.c | 157 -------------- > arch/arm64/kvm/Kconfig | 15 ++ > arch/arm64/kvm/arm.c | 2 +- > arch/arm64/kvm/handle_exit.c | 101 +++++++++ > arch/arm64/kvm/hyp/nvhe/Makefile | 2 +- > arch/arm64/kvm/hyp/nvhe/host.S | 9 +- > arch/arm64/kvm/hyp/nvhe/stacktrace.c | 116 +++++++++++ > arch/arm64/kvm/hyp/nvhe/switch.c | 6 + > 13 files changed, 749 insertions(+), 204 deletions(-) > create mode 100644 arch/arm64/include/asm/stacktrace/common.h > create mode 100644 arch/arm64/include/asm/stacktrace/nvhe.h > create mode 100644 arch/arm64/kvm/hyp/nvhe/stacktrace.c > > > base-commit: 82a592c13b0aeff94d84d54183dae0b26384c95f > -- > 2.37.0.170.g444d1eabd0-goog > _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
