From: <redacted> <redacted> Sent: Monday, July 29, 2019 12:53 AM
This is to prepare to add Hyper-V sched clock callback and move
Hyper-V reference TSC initialization much earlier in the boot
process when timestamp is 0. So no discontinuity is observed
when pv_ops.time.sched_clock to calculate its offset. This earlier
initialization requires that the Hyper-V TSC page be allocated
statically instead of with vmalloc(), so fixup the references
to the TSC page and the method of getting its physical address.
I'd suggest tweaking the commit message wording a bit:
Prepare to add Hyper-V sched clock callback and move Hyper-V
Reference TSC initialization much earlier in the boot process. Earlier
initialization is needed so that it happens while the timestamp value
is still 0 and no discontinuity in the timestamp will occur when
pv_ops.time.sched_clock calculates its offset. The earlier
initialization requires that the Hyper-V TSC page be allocated
statically instead of with vmalloc(), so fixup the references
to the TSC page and the method of getting its physical address.
quoted hunk ↗ jump to hunk
Signed-off-by: Tianyu Lan <redacted>
---
arch/x86/entry/vdso/vma.c | 2 +-
drivers/clocksource/hyperv_timer.c | 12 ++++--------
2 files changed, 5 insertions(+), 9 deletions(-)
@@ -280,12 +280,8 @@ static bool __init hv_init_tsc_clocksource(void)
if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
return false;
- tsc_pg = vmalloc(PAGE_SIZE);
- if (!tsc_pg)
- return false;
-
hyperv_cs = &hyperv_cs_tsc;
- phys_addr = page_to_phys(vmalloc_to_page(tsc_pg));
+ phys_addr = virt_to_phys(&tsc_pg) & PAGE_MASK;
The and'ing with PAGE_MASK isn't needed. You've set up tsc_pg
to ensure it is page aligned, so there's no need to mask out any
low order bits. That's why the previous code didn't do the masking
either.
/*
* The Hyper-V TLFS specifies to preserve the value of reserved
--
2.14.5