user/sven/linux.git/drivers/clocksource/hyperv_timer.c, branch v6.1.154

x86/hyperv: Fix hv tsc page based sched_clock for hibernation

2025-01-09T12:29:56Z

commit bcc80dec91ee745b3d66f3e48f0ec2efdea97149 upstream. read_hv_sched_clock_tsc() assumes that the Hyper-V clock counter is bigger than the variable hv_sched_clock_offset, which is cached during early boot, but depending on the timing this assumption may be false when a hibernated VM starts again (the clock counter starts from 0 again) and is resuming back (Note: hv_init_tsc_clocksource() is not called during hibernation/resume); consequently, read_hv_sched_clock_tsc() may return a negative integer (which is interpreted as a huge positive integer since the return type is u64) and new kernel messages are prefixed with huge timestamps before read_hv_sched_clock_tsc() grows big enough (which typically takes several seconds). Fix the issue by saving the Hyper-V clock counter just before the suspend, and using it to correct the hv_sched_clock_offset in resume. This makes hv tsc page based sched_clock continuous and ensures that post resume, it starts from where it left off during suspend. Override x86_platform.save_sched_clock_state and x86_platform.restore_sched_clock_state routines to correct this as soon as possible. Note: if Invariant TSC is available, the issue doesn't happen because 1) we don't register read_hv_sched_clock_tsc() for sched clock: See commit e5313f1c5404 ("clocksource/drivers/hyper-v: Rework clocksource and sched clock setup"); 2) the common x86 code adjusts TSC similarly: see __restore_processor_state() -> tsc_verify_tsc_adjust(true) and x86_platform.restore_sched_clock_state(). Cc: stable@vger.kernel.org Fixes: 1349401ff1aa ("clocksource/drivers/hyper-v: Suspend/resume Hyper-V clocksource for hibernation") Co-developed-by: Dexuan Cui Signed-off-by: Dexuan Cui Signed-off-by: Naman Jain Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20240917053917.76787-1-namjain@linux.microsoft.com Signed-off-by: Wei Liu Message-ID: <20240917053917.76787-1-namjain@linux.microsoft.com> Signed-off-by: Naman Jain Signed-off-by: Greg Kroah-Hartman

clocksource/drivers/hyperv: add data structure for reference TSC MSR

2022-11-03T15:50:28Z

Add a data structure to represent the reference TSC MSR similar to other MSRs. This simplifies the code for updating the MSR. Signed-off-by: Anirudh Rayabharam Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20221027095729.1676394-2-anrayabh@linux.microsoft.com Signed-off-by: Wei Liu

clocksource: hyper-v: unexport __init-annotated hv_init_clocksource()

2022-06-08T12:27:08Z

EXPORT_SYMBOL and __init is a bad combination because the .init.text section is freed up after the initialization. Hence, modules cannot use symbols annotated __init. The access to a freed symbol may end up with kernel panic. modpost used to detect it, but it has been broken for a decade. Recently, I fixed modpost so it started to warn it again, then this showed up in linux-next builds. There are two ways to fix it: - Remove __init - Remove EXPORT_SYMBOL I chose the latter for this case because the only in-tree call-site, arch/x86/kernel/cpu/mshyperv.c is never compiled as modular. (CONFIG_HYPERVISOR_GUEST is boolean) Fixes: dd2cb348613b ("clocksource/drivers: Continue making Hyper-V clocksource ISA agnostic") Reported-by: Stephen Rothwell Signed-off-by: Masahiro Yamada Reviewed-by: Vitaly Kuznetsov Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20220606050238.4162200-1-masahiroy@kernel.org Signed-off-by: Wei Liu

drivers: hv: Decouple Hyper-V clock/timer code from VMbus drivers

2021-07-19T09:24:28Z

Hyper-V clock/timer code in hyperv_timer.c is mostly independent from other VMbus drivers, but building for ARM64 without hyperv_timer.c shows some remaining entanglements. A default implementation of hv_read_reference_counter can just read a Hyper-V synthetic register and be independent of hyperv_timer.c, so move this code out and into hv_common.c. Then it can be used by the timesync driver even if hyperv_timer.c isn't built on a particular architecture. If hyperv_timer.c *is* built, it can override with a faster implementation. Also provide stubs for stimer functions called by the VMbus driver when hyperv_timer.c isn't built. No functional changes. Signed-off-by: Michael Kelley Link: https://lore.kernel.org/r/1626220906-22629-1-git-send-email-mikelley@microsoft.com Signed-off-by: Wei Liu

clocksource/drivers/hyper-v: Re-enable VDSO_CLOCKMODE_HVCLOCK on X86

2021-05-14T12:55:13Z

Mohammed reports (https://bugzilla.kernel.org/show_bug.cgi?id=213029) the commit e4ab4658f1cf ("clocksource/drivers/hyper-v: Handle vDSO differences inline") broke vDSO on x86. The problem appears to be that VDSO_CLOCKMODE_HVCLOCK is an enum value in 'enum vdso_clock_mode' and '#ifdef VDSO_CLOCKMODE_HVCLOCK' branch evaluates to false (it is not a define). Use a dedicated HAVE_VDSO_CLOCKMODE_HVCLOCK define instead. Fixes: e4ab4658f1cf ("clocksource/drivers/hyper-v: Handle vDSO differences inline") Reported-by: Mohammed Gamal Suggested-by: Thomas Gleixner Signed-off-by: Vitaly Kuznetsov Signed-off-by: Thomas Gleixner Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20210513073246.1715070-1-vkuznets@redhat.com

Merge tag 'hyperv-next-signed-20210426' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux

2021-04-26T17:44:16Z

Pull Hyper-V updates from Wei Liu: - VMBus enhancement - Free page reporting support for Hyper-V balloon driver - Some patches for running Linux as Arm64 Hyper-V guest - A few misc clean-up patches * tag 'hyperv-next-signed-20210426' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux: (30 commits) drivers: hv: Create a consistent pattern for checking Hyper-V hypercall status x86/hyperv: Move hv_do_rep_hypercall to asm-generic video: hyperv_fb: Add ratelimit on error message Drivers: hv: vmbus: Increase wait time for VMbus unload Drivers: hv: vmbus: Initialize unload_event statically Drivers: hv: vmbus: Check for pending channel interrupts before taking a CPU offline Drivers: hv: vmbus: Drivers: hv: vmbus: Introduce CHANNELMSG_MODIFYCHANNEL_RESPONSE Drivers: hv: vmbus: Introduce and negotiate VMBus protocol version 5.3 Drivers: hv: vmbus: Use after free in __vmbus_open() Drivers: hv: vmbus: remove unused function Drivers: hv: vmbus: Remove unused linux/version.h header x86/hyperv: remove unused linux/version.h header x86/Hyper-V: Support for free page reporting x86/hyperv: Fix unused variable 'hi' warning in hv_apic_read x86/hyperv: Fix unused variable 'msr_val' warning in hv_qlock_wait hv: hyperv.h: a few mundane typo fixes drivers: hv: Fix EXPORT_SYMBOL and tab spaces issue Drivers: hv: vmbus: Drop error message when 'No request id available' asm-generic/hyperv: Add missing function prototypes per -W1 warnings clocksource/drivers/hyper-v: Move handling of STIMER0 interrupts ...

timekeeping, clocksource: Fix various typos in comments

2021-03-22T22:06:48Z

Fix ~56 single-word typos in timekeeping & clocksource code comments. Signed-off-by: Ingo Molnar Cc: Thomas Gleixner Cc: John Stultz Cc: Stephen Boyd Cc: Daniel Lezcano Cc: linux-kernel@vger.kernel.org

clocksource/drivers/hyper-v: Move handling of STIMER0 interrupts

2021-03-08T17:33:00Z

STIMER0 interrupts are most naturally modeled as per-cpu IRQs. But because x86/x64 doesn't have per-cpu IRQs, the core STIMER0 interrupt handling machinery is done in code under arch/x86 and Linux IRQs are not used. Adding support for ARM64 means adding equivalent code using per-cpu IRQs under arch/arm64. A better model is to treat per-cpu IRQs as the normal path (which it is for modern architectures), and the x86/x64 path as the exception. Do this by incorporating standard Linux per-cpu IRQ allocation into the main SITMER0 driver code, and bypass it in the x86/x64 exception case. For x86/x64, special case code is retained under arch/x86, but no STIMER0 interrupt handling code is needed under arch/arm64. No functional change. Signed-off-by: Michael Kelley Acked-by: Daniel Lezcano Link: https://lore.kernel.org/r/1614721102-2241-11-git-send-email-mikelley@microsoft.com Signed-off-by: Wei Liu

clocksource/drivers/hyper-v: Set clocksource rating based on Hyper-V feature

2021-03-08T17:33:00Z

On x86/x64, the TSC clocksource is available in a Hyper-V VM only if Hyper-V provides the TSC_INVARIANT flag. The rating on the Hyper-V Reference TSC page clocksource is currently set so that it will not override the TSC clocksource in this case. Alternatively, if the TSC clocksource is not available, then the Hyper-V clocksource is used. But on ARM64, the Hyper-V Reference TSC page clocksource should override the ARM arch counter, since the Hyper-V clocksource provides scaling and offsetting during live migrations that is not provided for the ARM arch counter. To get the needed behavior for both x86/x64 and ARM64, tweak the logic by defaulting the Hyper-V Reference TSC page clocksource rating to a large value that will always override. If the Hyper-V TSC_INVARIANT flag is set, then reduce the rating so that it will not override the TSC. While the logic for getting there is slightly different, the net result in the normal cases is no functional change. Signed-off-by: Michael Kelley Acked-by: Daniel Lezcano Link: https://lore.kernel.org/r/1614721102-2241-10-git-send-email-mikelley@microsoft.com Signed-off-by: Wei Liu

clocksource/drivers/hyper-v: Handle sched_clock differences inline

2021-03-08T17:33:00Z

While the Hyper-V Reference TSC code is architecture neutral, the pv_ops.time.sched_clock() function is implemented for x86/x64, but not for ARM64. Current code calls a utility function under arch/x86 (and coming, under arch/arm64) to handle the difference. Change this approach to handle the difference inline based on whether GENERIC_SCHED_CLOCK is present. The new approach removes code under arch/* since the difference is tied more to the specifics of the Linux implementation than to the architecture. No functional change. Signed-off-by: Michael Kelley Reviewed-by: Boqun Feng Acked-by: Daniel Lezcano Link: https://lore.kernel.org/r/1614721102-2241-9-git-send-email-mikelley@microsoft.com Signed-off-by: Wei Liu