On Fri, Jul 15, 2022 at 6:55 AM 'Fuad Tabba' via kernel-team <kernel-team@xxxxxxxxxxx> wrote: > > Hi Kalesh, > > On Fri, Jul 15, 2022 at 7:10 AM Kalesh Singh <kaleshsingh@xxxxxxxxxx> wrote: > > > > Hi all, > > > > This is v4 of the series adding support for nVHE hypervisor stacktraces; > > and is based on arm64 for-next/stacktrace. > > > > Thanks all for your feedback on previous revisions. Mark Brown, I > > appreciate your Reviewed-by on the v3, I have dropped the tags in this > > new verision since I think the series has changed quite a bit. > > > > The previous versions were posted at: > > 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 to address concerens from Marc on the > > memory usage and reusing the common code by refactoring into a shared header. > > > > Thanks, > > Kalesh > > I tested an earlier version of this patch series, and it worked fine, > with symbolization. However, testing it now, both with nvhe and with > pkvm the symbolization isn't working for me. e.g. > > [ 32.986706] kvm [251]: Protected nVHE HYP call trace: > [ 32.986796] kvm [251]: [<ffff800008f8b0e0>] 0xffff800008f8b0e0 > [ 32.987391] kvm [251]: [<ffff800008f8b388>] 0xffff800008f8b388 > [ 32.987493] kvm [251]: [<ffff800008f8d230>] 0xffff800008f8d230 > [ 32.987591] kvm [251]: [<ffff800008f8d51c>] 0xffff800008f8d51c > [ 32.987695] kvm [251]: [<ffff800008f8c064>] 0xffff800008f8c064 > [ 32.987803] kvm [251]: ---- End of Protected nVHE HYP call trace ---- > > CONFIG_PROTECTED_NVHE_STACKTRACE CONFIG_NVHE_EL2_DEBUG and > CONFIG_DEBUG_INFO_DWARF_TOOLCHAIN_DEFAULT are all enabled. Generating > a backtrace in the host I get proper symbolisation. > > Is there anything else you'd like to know about my setup that would > help get to the bottom of this? Hi Fuad, Thanks for reviewing it. Can you attach the .config when you have a chance please? I will try reproducing it on my end. --Kalesh > > Thanks, > /fuad > > > > > > > > ============ > > > > 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 hyperviosr 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 > > hyperviosr 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 (18): > > 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() > > KVM: arm64: Dump nVHE hypervisor stack on panic > > > > arch/arm64/include/asm/kvm_asm.h | 16 ++ > > arch/arm64/include/asm/memory.h | 7 + > > arch/arm64/include/asm/stacktrace.h | 92 ++++--- > > arch/arm64/include/asm/stacktrace/common.h | 224 ++++++++++++++++ > > arch/arm64/include/asm/stacktrace/nvhe.h | 291 +++++++++++++++++++++ > > arch/arm64/kernel/stacktrace.c | 157 ----------- > > arch/arm64/kvm/Kconfig | 15 ++ > > arch/arm64/kvm/arm.c | 2 +- > > arch/arm64/kvm/handle_exit.c | 4 + > > arch/arm64/kvm/hyp/nvhe/Makefile | 2 +- > > arch/arm64/kvm/hyp/nvhe/host.S | 9 +- > > arch/arm64/kvm/hyp/nvhe/stacktrace.c | 108 ++++++++ > > arch/arm64/kvm/hyp/nvhe/switch.c | 5 + > > 13 files changed, 727 insertions(+), 205 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 > > > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@xxxxxxxxxxx. > _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
