| Message ID | 20220210224220.4076151-1-kaleshsingh@google.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | KVM: arm64: Hypervisor stack enhancements | expand |
On Thu, 10 Feb 2022 22:41:41 +0000, Kalesh Singh <kaleshsingh@google.com> wrote: > > This series is based on v5.17-rc3 and adds the following stack features to > the KVM nVHE hypervisor: > > == Hyp Stack Guard Pages == > > Based on the technique used by arm64 VMAP_STACK to detect overflow. > i.e. the stack is aligned to twice its size which ensure that the > 'stack shift' bit of any valid SP is 0. The 'stack shift' bit can be > tested in the exception entry to detect overflow without corrupting GPRs. Having quickly parsed the code, this seems to only be effective for pKVM and the EL2-allocated stack. Is there any technical reason not to implement this for the much more common case of 'classic' KVM in nVHE mode? Thanks, M.
On Mon, Feb 14, 2022 at 3:41 AM Marc Zyngier <maz@kernel.org> wrote: > > On Thu, 10 Feb 2022 22:41:41 +0000, > Kalesh Singh <kaleshsingh@google.com> wrote: > > > > This series is based on v5.17-rc3 and adds the following stack features to > > the KVM nVHE hypervisor: > > > > == Hyp Stack Guard Pages == > > > > Based on the technique used by arm64 VMAP_STACK to detect overflow. > > i.e. the stack is aligned to twice its size which ensure that the > > 'stack shift' bit of any valid SP is 0. The 'stack shift' bit can be > > tested in the exception entry to detect overflow without corrupting GPRs. > > Having quickly parsed the code, this seems to only be effective for > pKVM and the EL2-allocated stack. Is there any technical reason not to > implement this for the much more common case of 'classic' KVM in nVHE > mode? Hi Marc, No technical reason. We hadn't thought of it from that perspective. It's a good idea, I'll look into this and repost a new version. Thanks, Kalesh > > Thanks, > > M. > > -- > Without deviation from the norm, progress is not possible.
This series is based on v5.17-rc3 and adds the following stack features to the KVM nVHE hypervisor: == Hyp Stack Guard Pages == Based on the technique used by arm64 VMAP_STACK to detect overflow. i.e. the stack is aligned to twice its size which ensure that the 'stack shift' bit of any valid SP is 0. The 'stack shift' bit can be tested in the exception entry to detect overflow without corrupting GPRs. == Hyp Stack Unwinder == Based on the arm64 kernel stack unwinder (See: arch/arm64/kernel/stacktrace.c) The unwinding and dumping of the hyp stack is not enabled by default and depends on CONFIG_NVHE_EL2_DEBUG to avoid potential information leaks. When CONFIG_NVHE_EL2_DEBUG is enabled the host stage 2 protection is disabled, allowing the host to read the hypervisor stack pages and unwind the stack from EL1. This allows us to print the hypervisor stacktrace before panicking the host; as shown below: kvm [408]: nVHE hyp panic at: \ [<ffffffc01161460c>] __kvm_nvhe_overflow_stack+0x10/0x34! kvm [408]: nVHE HYP call trace: kvm [408]: [<ffffffc011614974>] __kvm_nvhe_hyp_panic_bad_stack+0xc/0x10 kvm [408]: [<ffffffc01160fa48>] __kvm_nvhe___kvm_hyp_host_vector+0x248/0x794 kvm [408]: [<ffffffc01161461c>] __kvm_nvhe_overflow_stack+0x20/0x34 . . . kvm [408]: [<ffffffc01161461c>] __kvm_nvhe_overflow_stack+0x20/0x34 kvm [408]: [<ffffffc01161421c>] __kvm_nvhe___kvm_vcpu_run+0x2c/0x40c kvm [408]: [<ffffffc011615e14>] __kvm_nvhe_handle___kvm_vcpu_run+0x1c8/0x36c kvm [408]: [<ffffffc0116157c4>] __kvm_nvhe_handle_trap+0xa4/0x124 kvm [408]: [<ffffffc01160f060>] __kvm_nvhe___host_exit+0x60/0x64 kvm [408]: ---- end of nVHE HYP call trace ---- Kalesh Singh (3): KVM: arm64: Add Hyp overflow stack KVM: arm64: Unwind and dump nVHE HYP stacktrace KVM: arm64: Symbolize the nVHE HYP backtrace Quentin Perret (4): KVM: arm64: Map the stack pages in the 'private' range KVM: arm64: Factor out private range VA allocation arm64: asm: Introduce test_sp_overflow macro KVM: arm64: Allocate guard pages near hyp stacks arch/arm64/include/asm/assembler.h | 11 + arch/arm64/include/asm/kvm_asm.h | 17 ++ arch/arm64/kernel/entry.S | 9 +- arch/arm64/kvm/Makefile | 1 + arch/arm64/kvm/arm.c | 2 +- arch/arm64/kvm/handle_exit.c | 14 +- arch/arm64/kvm/hyp/include/nvhe/mm.h | 1 + arch/arm64/kvm/hyp/nvhe/host.S | 21 ++ arch/arm64/kvm/hyp/nvhe/mm.c | 28 ++- arch/arm64/kvm/hyp/nvhe/setup.c | 63 +++++- arch/arm64/kvm/hyp/nvhe/switch.c | 22 ++ arch/arm64/kvm/stacktrace.c | 290 +++++++++++++++++++++++++++ arch/arm64/kvm/stacktrace.h | 17 ++ scripts/kallsyms.c | 2 +- 14 files changed, 468 insertions(+), 30 deletions(-) create mode 100644 arch/arm64/kvm/stacktrace.c create mode 100644 arch/arm64/kvm/stacktrace.h base-commit: dfd42facf1e4ada021b939b4e19c935dcdd55566