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| author | Andrey Smetanin <asmetanin@virtuozzo.com> | 2015-12-14 16:01:55 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-12-14 19:15:05 -0800 |
| commit | c35b82ef0294ae5052120615f5cfcef17c5a6bf7 (patch) | |
| tree | 25b78f6815b620598fc284e1342c0b65bd5f37b1 /drivers/hv | |
| parent | 8599846d73997cdbccf63f23394d871cfad1e5e6 (diff) | |
| download | linux-c35b82ef0294ae5052120615f5cfcef17c5a6bf7.tar.gz linux-c35b82ef0294ae5052120615f5cfcef17c5a6bf7.tar.bz2 linux-c35b82ef0294ae5052120615f5cfcef17c5a6bf7.zip | |
drivers/hv: correct tsc page sequence invalid value
Hypervisor Top Level Functional Specification v3/4 says
that TSC page sequence value = -1(0xFFFFFFFF) is used to
indicate that TSC page no longer reliable source of reference
timer. Unfortunately, we found that Windows Hyper-V guest
side implementation uses sequence value = 0 to indicate
that Tsc page no longer valid. This is clearly visible
inside Windows 2012R2 ntoskrnl.exe HvlGetReferenceTime()
function dissassembly:
HvlGetReferenceTime proc near
xchg ax, ax
loc_1401C3132:
mov rax, cs:HvlpReferenceTscPage
mov r9d, [rax]
test r9d, r9d
jz short loc_1401C3176
rdtsc
mov rcx, cs:HvlpReferenceTscPage
shl rdx, 20h
or rdx, rax
mov rax, [rcx+8]
mov rcx, cs:HvlpReferenceTscPage
mov r8, [rcx+10h]
mul rdx
mov rax, cs:HvlpReferenceTscPage
add rdx, r8
mov ecx, [rax]
cmp ecx, r9d
jnz short loc_1401C3132
jmp short loc_1401C3184
loc_1401C3176:
mov ecx, 40000020h
rdmsr
shl rdx, 20h
or rdx, rax
loc_1401C3184:
mov rax, rdx
retn
HvlGetReferenceTime endp
This patch aligns Tsc page invalid sequence value with
Windows Hyper-V guest implementation which is more
compatible with both Hyper-V hypervisor and KVM hypervisor.
Signed-off-by: Andrey Smetanin <asmetanin@virtuozzo.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/hv')
| -rw-r--r-- | drivers/hv/hv.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c index eb4e383dbc58..11bca51ef5ff 100644 --- a/drivers/hv/hv.c +++ b/drivers/hv/hv.c @@ -140,7 +140,7 @@ static cycle_t read_hv_clock_tsc(struct clocksource *arg) cycle_t current_tick; struct ms_hyperv_tsc_page *tsc_pg = hv_context.tsc_page; - if (tsc_pg->tsc_sequence != -1) { + if (tsc_pg->tsc_sequence != 0) { /* * Use the tsc page to compute the value. */ @@ -162,7 +162,7 @@ static cycle_t read_hv_clock_tsc(struct clocksource *arg) if (tsc_pg->tsc_sequence == sequence) return current_tick; - if (tsc_pg->tsc_sequence != -1) + if (tsc_pg->tsc_sequence != 0) continue; /* * Fallback using MSR method. |