diff options
| author | Dexuan Cui <decui@microsoft.com> | 2024-06-20 23:16:14 -0700 |
|---|---|---|
| committer | Wei Liu <wei.liu@kernel.org> | 2024-06-24 07:06:29 +0000 |
| commit | 7f828d5fff7d24752e1ecf6bebb6617a81f97b93 (patch) | |
| tree | 1a80c4c22362f09a6597d122d0faf604847acc0c /drivers/clocksource | |
| parent | 90ac806c32952e4eb39fa21cc4e93f086a4047c3 (diff) | |
| download | lwn-7f828d5fff7d24752e1ecf6bebb6617a81f97b93.tar.gz lwn-7f828d5fff7d24752e1ecf6bebb6617a81f97b93.zip | |
clocksource: hyper-v: Use lapic timer in a TDX VM without paravisor
In a TDX VM without paravisor, currently the default timer is the Hyper-V
timer, which depends on the slow VM Reference Counter MSR: the Hyper-V TSC
page is not enabled in such a VM because the VM uses Invariant TSC as a
better clocksource and it's challenging to mark the Hyper-V TSC page shared
in very early boot.
Lower the rating of the Hyper-V timer so the local APIC timer becomes the
the default timer in such a VM, and print a warning in case Invariant TSC
is unavailable in such a VM. This change should cause no perceivable
performance difference.
Cc: stable@vger.kernel.org # 6.6+
Reviewed-by: Roman Kisel <romank@linux.microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20240621061614.8339-1-decui@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20240621061614.8339-1-decui@microsoft.com>
Diffstat (limited to 'drivers/clocksource')
| -rw-r--r-- | drivers/clocksource/hyperv_timer.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c index b2a080647e41..99177835cade 100644 --- a/drivers/clocksource/hyperv_timer.c +++ b/drivers/clocksource/hyperv_timer.c @@ -137,7 +137,21 @@ static int hv_stimer_init(unsigned int cpu) ce->name = "Hyper-V clockevent"; ce->features = CLOCK_EVT_FEAT_ONESHOT; ce->cpumask = cpumask_of(cpu); - ce->rating = 1000; + + /* + * Lower the rating of the Hyper-V timer in a TDX VM without paravisor, + * so the local APIC timer (lapic_clockevent) is the default timer in + * such a VM. The Hyper-V timer is not preferred in such a VM because + * it depends on the slow VM Reference Counter MSR (the Hyper-V TSC + * page is not enbled in such a VM because the VM uses Invariant TSC + * as a better clocksource and it's challenging to mark the Hyper-V + * TSC page shared in very early boot). + */ + if (!ms_hyperv.paravisor_present && hv_isolation_type_tdx()) + ce->rating = 90; + else + ce->rating = 1000; + ce->set_state_shutdown = hv_ce_shutdown; ce->set_state_oneshot = hv_ce_set_oneshot; ce->set_next_event = hv_ce_set_next_event; |