Messages in this thread | | | Date | Tue, 1 Feb 2022 15:02:33 +0100 | Subject | Re: [PATCH v3 0/5] kvm: fix latent guest entry/exit bugs | From | Christian Borntraeger <> |
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Am 01.02.22 um 14:29 schrieb Mark Rutland: > Several architectures have latent bugs around guest entry/exit, > including:
Thanks for looking into this.
> > 1) Enabling interrupts during an RCU EQS, allowing interrupt handlers to > run without RCU watching. > > 2) Using (potentially) instrumented code between guest_enter() and > guest_exit(), allowing instrumentation handlers to run without RCU > watching. > > 3) Not informing lockdep and tracing about interrupt masking, or > informing in an incorrect order (e.g. relative to entering/exiting an > RCU EQS). > > 4) Unbalanced entry/exit accounting in some cases (which may or may not > result in functional problems). > > Overall, the architectures affected are: > > arm64, mips, powerpc, riscv, s390, x86 > > This series reworks the common code to make handling these issues > earier, and for the following architectures fixes those issues by > conversion to new helper functions: > > arm64, mips, riscv, x86 > > The core, arm64, and x86 patches have reviews from the relevant > maintainers, and I think those are good-to-go. I have not yet had > acks/reviews for the mips and riscv patches. I'm fairly certain the > riscv patch is correct by virtue of it being so simple, and I'm > relatively confident that the mips patch is correct (though I may have > missed additional issues), but I have no way of testing either so I've > placed them at the end of the series where they can easily be dropped if > necessary. > > This series does NOT fix the following architectures, which will need > more substantial changes to architecture-specific entry logic and/or > sequencing: > > powerpc, s390
Right, s390 is more complicated as we need to modify the page fault handling. For the time being we should be as bad/good as before with the deprecated old guest_enter/exit_irqoff. I will test this to be sure.
> > ... and I assume it would be preferable to fix the common code and > simple cases now, such that those can be addressed in subsequent > follow-ups. > > Since v1 [1]: > * Add arch_in_rcu_eqs() > * Convert s390 > * Rename exit_to_guest_mode() -> guest_state_enter_irqoff() > * Rename enter_from_guest_mode() -> guest_state_exit_irqoff() > * Various commit message cleanups > > Since v2 [2]: > * Rebase to v5.17-rc2 > * Fixup mips exit handling > * Drop arch_in_rcu_eqs() & s390 patches > > I've pushed the series (based on v5.17-rc2) to my kvm/entry-rework branch: > > https://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git/log/?h=kvm/entry-rework > git://git.kernel.org/pub/scm/linux/kernel/git/mark/linux.git kvm/entry-rework > > This version of the series is tagged as kvm-entry-rework-20220201. > > [1] https://lore.kernel.org/r/20220111153539.2532246-1-mark.rutland@arm.com/ > [2] https://lore.kernel.org/r/20220119105854.3160683-1-mark.rutland@arm.com/ > > Thanks, > > > Mark Rutland (5): > kvm: add guest_state_{enter,exit}_irqoff() > kvm/arm64: rework guest entry logic > kvm/x86: rework guest entry logic > kvm/riscv: rework guest entry logic > kvm/mips: rework guest entry logic > > arch/arm64/kvm/arm.c | 51 +++++++++++------- > arch/mips/kvm/mips.c | 50 +++++++++++++++-- > arch/riscv/kvm/vcpu.c | 44 +++++++++------ > arch/x86/kvm/svm/svm.c | 4 +- > arch/x86/kvm/vmx/vmx.c | 4 +- > arch/x86/kvm/x86.c | 4 +- > arch/x86/kvm/x86.h | 45 ---------------- > include/linux/kvm_host.h | 112 +++++++++++++++++++++++++++++++++++++-- > 8 files changed, 222 insertions(+), 92 deletions(-) >
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