From mboxrd@z Thu Jan 1 00:00:00 1970 From: zhichao.huang@linaro.org (Zhichao Huang) Date: Mon, 10 Aug 2015 21:25:52 +0800 Subject: [PATCH v4 00/15] KVM: arm: debug infrastructure support Message-ID: <1439213167-8988-1-git-send-email-zhichao.huang@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org This patch series adds debug support, a key feature missing from the KVM/armv7 port. The main idea is to keep track of whether the host and the guest have any break/watch points enabled or not. We only do the world switch for debug registers when the host or the guest is actually using it. We add a function reading the break/watch control variables directly to indicate whether the host has enabled any break/watch points or not. We only call the function upon guest entry, after preempt_disable() and local_irq_disable(), so there is no race for it. We also tried implementing this series with trapping host use of debug registers to hyp mode, and keep track of host/guest use of the debug hardware in that way. This, however, proved to be very difficult, because it requires us to: First, we have to add a new mechanism to support trapping host, jump from EL2 to EL1 to run our host_trap_handlers, and then jump back to the orginal code which trigger the trap. Second, we have to take specail care when tearing down KVM to disable the traps, we also impose an ordering requirement of whether KVM or the breakpoint functionality gets initialized first. In the end we decided that this was too difficult and convoluted compared to simply read the values from variables, so we reverted back to this approach. The amount of registers is properly frightening, but CPUs actually only implement a subset of them. Also, there is a number of registers we don't bother emulating (things having to do with external debug and OSlock). External debug is when you actually plug a physical JTAG into the CPU. OSlock is a way to prevent "other software" to play with the debug registers. My understanding is that it is only useful in combination with the external debug. In both case, implementing support for this is probably not worth the effort, at least for the time being. This has been tested on a Cortex-A15 platform, running 32bit guests. The patches for this series are based off v4.2-rc6 and can be found at: https://git.linaro.org/people/zhichao.huang/linux.git branch: guest-debug/4.2-rc6-v4 >>From v3 [3]: - Redefine kvm_cpu_context_t as a new struct including the cp14 states - Save host cp14 states in the vcpu struct intead of memory - Add a function to keep track of the host use of the debug registers - Add new lazy world switch mechanism >>From v2 [2]: - Delete the debug mode enabling/disabling strategy - Add missing cp14/cp15 trace events >>From v1 [1]: - Added missing cp14 reset functions - Disable debug mode if we don't need it to reduce unnecessary switch [1]: https://lists.cs.columbia.edu/pipermail/kvmarm/2015-May/014729.html [2]: https://lists.cs.columbia.edu/pipermail/kvmarm/2015-May/014847.html [3]: https://lists.cs.columbia.edu/pipermail/kvmarm/2015-June/015167.html Zhichao Huang (15): KVM: arm: plug guest debug exploit KVM: arm: rename pm_fake handler to trap_raz_wi KVM: arm: enable to use the ARM_DSCR_MDBGEN macro from KVM assembly code KVM: arm: common infrastructure for handling AArch32 CP14/CP15 KVM: arm: check ordering of all system register tables KVM: arm: add trap handlers for 32-bit debug registers KVM: arm: add trap handlers for 64-bit debug registers KVM: arm: add a trace event for cp14 traps KVM: arm: redefine kvm_cpu_context_t to save the host cp14 states KVM: arm: implement world switch for debug registers KVM: arm: add a function to keep track of host use of the debug registers KVM: arm: keep track of host use of the debug registers KVM: arm: keep track of guest use of the debug registers KVM: arm: implement lazy world switch for debug registers KVM: arm: enable trapping of all debug registers arch/arm/include/asm/hw_breakpoint.h | 59 +++-- arch/arm/include/asm/kvm_asm.h | 17 ++ arch/arm/include/asm/kvm_coproc.h | 3 +- arch/arm/include/asm/kvm_host.h | 13 +- arch/arm/kernel/asm-offsets.c | 6 +- arch/arm/kernel/hw_breakpoint.c | 21 ++ arch/arm/kvm/arm.c | 2 + arch/arm/kvm/coproc.c | 445 ++++++++++++++++++++++++++++++----- arch/arm/kvm/handle_exit.c | 4 +- arch/arm/kvm/interrupts.S | 18 +- arch/arm/kvm/interrupts_head.S | 188 ++++++++++++++- arch/arm/kvm/trace.h | 30 +++ arch/arm64/include/asm/kvm_host.h | 1 + 13 files changed, 707 insertions(+), 100 deletions(-) -- 1.7.12.4