From: Greg Kroah-Hartman Date: Mon, 7 Feb 2022 13:38:00 +0000 (+0100) Subject: 5.15-stable patches X-Git-Tag: v4.9.300~2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8e4227d05d078f7163f45932cef2d4c81e1aa154;p=thirdparty%2Fkernel%2Fstable-queue.git 5.15-stable patches added patches: kvm-add-guest_state_-enter-exit-_irqoff.patch --- diff --git a/queue-5.15/kvm-add-guest_state_-enter-exit-_irqoff.patch b/queue-5.15/kvm-add-guest_state_-enter-exit-_irqoff.patch new file mode 100644 index 00000000000..3a50c96b459 --- /dev/null +++ b/queue-5.15/kvm-add-guest_state_-enter-exit-_irqoff.patch @@ -0,0 +1,238 @@ +From ef9989afda73332df566852d6e9ca695c05f10ce Mon Sep 17 00:00:00 2001 +From: Mark Rutland +Date: Tue, 1 Feb 2022 13:29:22 +0000 +Subject: kvm: add guest_state_{enter,exit}_irqoff() + +From: Mark Rutland + +commit ef9989afda73332df566852d6e9ca695c05f10ce upstream. + +When transitioning to/from guest mode, it is necessary to inform +lockdep, tracing, and RCU in a specific order, similar to the +requirements for transitions to/from user mode. Additionally, it is +necessary to perform vtime accounting for a window around running the +guest, with RCU enabled, such that timer interrupts taken from the guest +can be accounted as guest time. + +Most architectures don't handle all the necessary pieces, and a have a +number of common bugs, including unsafe usage of RCU during the window +between guest_enter() and guest_exit(). + +On x86, this was dealt with across commits: + + 87fa7f3e98a1310e ("x86/kvm: Move context tracking where it belongs") + 0642391e2139a2c1 ("x86/kvm/vmx: Add hardirq tracing to guest enter/exit") + 9fc975e9efd03e57 ("x86/kvm/svm: Add hardirq tracing on guest enter/exit") + 3ebccdf373c21d86 ("x86/kvm/vmx: Move guest enter/exit into .noinstr.text") + 135961e0a7d555fc ("x86/kvm/svm: Move guest enter/exit into .noinstr.text") + 160457140187c5fb ("KVM: x86: Defer vtime accounting 'til after IRQ handling") + bc908e091b326467 ("KVM: x86: Consolidate guest enter/exit logic to common helpers") + +... but those fixes are specific to x86, and as the resulting logic +(while correct) is split across generic helper functions and +x86-specific helper functions, it is difficult to see that the +entry/exit accounting is balanced. + +This patch adds generic helpers which architectures can use to handle +guest entry/exit consistently and correctly. The guest_{enter,exit}() +helpers are split into guest_timing_{enter,exit}() to perform vtime +accounting, and guest_context_{enter,exit}() to perform the necessary +context tracking and RCU management. The existing guest_{enter,exit}() +heleprs are left as wrappers of these. + +Atop this, new guest_state_enter_irqoff() and guest_state_exit_irqoff() +helpers are added to handle the ordering of lockdep, tracing, and RCU +manageent. These are inteneded to mirror exit_to_user_mode() and +enter_from_user_mode(). + +Subsequent patches will migrate architectures over to the new helpers, +following a sequence: + + guest_timing_enter_irqoff(); + + guest_state_enter_irqoff(); + < run the vcpu > + guest_state_exit_irqoff(); + + < take any pending IRQs > + + guest_timing_exit_irqoff(); + +This sequences handles all of the above correctly, and more clearly +balances the entry and exit portions, making it easier to understand. + +The existing helpers are marked as deprecated, and will be removed once +all architectures have been converted. + +There should be no functional change as a result of this patch. + +Signed-off-by: Mark Rutland +Reviewed-by: Marc Zyngier +Reviewed-by: Paolo Bonzini +Reviewed-by: Nicolas Saenz Julienne +Message-Id: <20220201132926.3301912-2-mark.rutland@arm.com> +Signed-off-by: Paolo Bonzini +Signed-off-by: Greg Kroah-Hartman +--- + include/linux/kvm_host.h | 112 +++++++++++++++++++++++++++++++++++++++++++++-- + 1 file changed, 109 insertions(+), 3 deletions(-) + +--- a/include/linux/kvm_host.h ++++ b/include/linux/kvm_host.h +@@ -15,6 +15,8 @@ + #include + #include + #include ++#include ++#include + #include + #include + #include +@@ -363,8 +365,11 @@ struct kvm_vcpu { + int last_used_slot; + }; + +-/* must be called with irqs disabled */ +-static __always_inline void guest_enter_irqoff(void) ++/* ++ * Start accounting time towards a guest. ++ * Must be called before entering guest context. ++ */ ++static __always_inline void guest_timing_enter_irqoff(void) + { + /* + * This is running in ioctl context so its safe to assume that it's the +@@ -373,7 +378,18 @@ static __always_inline void guest_enter_ + instrumentation_begin(); + vtime_account_guest_enter(); + instrumentation_end(); ++} + ++/* ++ * Enter guest context and enter an RCU extended quiescent state. ++ * ++ * Between guest_context_enter_irqoff() and guest_context_exit_irqoff() it is ++ * unsafe to use any code which may directly or indirectly use RCU, tracing ++ * (including IRQ flag tracing), or lockdep. All code in this period must be ++ * non-instrumentable. ++ */ ++static __always_inline void guest_context_enter_irqoff(void) ++{ + /* + * KVM does not hold any references to rcu protected data when it + * switches CPU into a guest mode. In fact switching to a guest mode +@@ -389,16 +405,79 @@ static __always_inline void guest_enter_ + } + } + +-static __always_inline void guest_exit_irqoff(void) ++/* ++ * Deprecated. Architectures should move to guest_timing_enter_irqoff() and ++ * guest_state_enter_irqoff(). ++ */ ++static __always_inline void guest_enter_irqoff(void) ++{ ++ guest_timing_enter_irqoff(); ++ guest_context_enter_irqoff(); ++} ++ ++/** ++ * guest_state_enter_irqoff - Fixup state when entering a guest ++ * ++ * Entry to a guest will enable interrupts, but the kernel state is interrupts ++ * disabled when this is invoked. Also tell RCU about it. ++ * ++ * 1) Trace interrupts on state ++ * 2) Invoke context tracking if enabled to adjust RCU state ++ * 3) Tell lockdep that interrupts are enabled ++ * ++ * Invoked from architecture specific code before entering a guest. ++ * Must be called with interrupts disabled and the caller must be ++ * non-instrumentable. ++ * The caller has to invoke guest_timing_enter_irqoff() before this. ++ * ++ * Note: this is analogous to exit_to_user_mode(). ++ */ ++static __always_inline void guest_state_enter_irqoff(void) ++{ ++ instrumentation_begin(); ++ trace_hardirqs_on_prepare(); ++ lockdep_hardirqs_on_prepare(CALLER_ADDR0); ++ instrumentation_end(); ++ ++ guest_context_enter_irqoff(); ++ lockdep_hardirqs_on(CALLER_ADDR0); ++} ++ ++/* ++ * Exit guest context and exit an RCU extended quiescent state. ++ * ++ * Between guest_context_enter_irqoff() and guest_context_exit_irqoff() it is ++ * unsafe to use any code which may directly or indirectly use RCU, tracing ++ * (including IRQ flag tracing), or lockdep. All code in this period must be ++ * non-instrumentable. ++ */ ++static __always_inline void guest_context_exit_irqoff(void) + { + context_tracking_guest_exit(); ++} + ++/* ++ * Stop accounting time towards a guest. ++ * Must be called after exiting guest context. ++ */ ++static __always_inline void guest_timing_exit_irqoff(void) ++{ + instrumentation_begin(); + /* Flush the guest cputime we spent on the guest */ + vtime_account_guest_exit(); + instrumentation_end(); + } + ++/* ++ * Deprecated. Architectures should move to guest_state_exit_irqoff() and ++ * guest_timing_exit_irqoff(). ++ */ ++static __always_inline void guest_exit_irqoff(void) ++{ ++ guest_context_exit_irqoff(); ++ guest_timing_exit_irqoff(); ++} ++ + static inline void guest_exit(void) + { + unsigned long flags; +@@ -408,6 +487,33 @@ static inline void guest_exit(void) + local_irq_restore(flags); + } + ++/** ++ * guest_state_exit_irqoff - Establish state when returning from guest mode ++ * ++ * Entry from a guest disables interrupts, but guest mode is traced as ++ * interrupts enabled. Also with NO_HZ_FULL RCU might be idle. ++ * ++ * 1) Tell lockdep that interrupts are disabled ++ * 2) Invoke context tracking if enabled to reactivate RCU ++ * 3) Trace interrupts off state ++ * ++ * Invoked from architecture specific code after exiting a guest. ++ * Must be invoked with interrupts disabled and the caller must be ++ * non-instrumentable. ++ * The caller has to invoke guest_timing_exit_irqoff() after this. ++ * ++ * Note: this is analogous to enter_from_user_mode(). ++ */ ++static __always_inline void guest_state_exit_irqoff(void) ++{ ++ lockdep_hardirqs_off(CALLER_ADDR0); ++ guest_context_exit_irqoff(); ++ ++ instrumentation_begin(); ++ trace_hardirqs_off_finish(); ++ instrumentation_end(); ++} ++ + static inline int kvm_vcpu_exiting_guest_mode(struct kvm_vcpu *vcpu) + { + /* diff --git a/queue-5.15/series b/queue-5.15/series index 4c69c3fcff7..b95fcd61fb3 100644 --- a/queue-5.15/series +++ b/queue-5.15/series @@ -89,6 +89,7 @@ selftests-futex-use-variable-make-instead-of-make.patch tools-resolve_btfids-do-not-print-any-commands-when-building-silently.patch e1000e-separate-adp-board-type-from-tgp.patch rtc-cmos-evaluate-century-appropriate.patch +kvm-add-guest_state_-enter-exit-_irqoff.patch kvm-arm64-rework-guest-entry-logic.patch perf-copy-perf_event_attr-sig_data-on-modification.patch perf-stat-fix-display-of-grouped-aliased-events.patch