[PATCH 1/1] drivers/hv: correct tsc page sequence invalid value
Denis V. Lunev
den at openvz.org
Thu Nov 12 07:16:19 UTC 2015
On 11/02/2015 10:42 PM, KY Srinivasan wrote:
>
>> -----Original Message-----
>> From: Denis V. Lunev [mailto:den at openvz.org]
>> Sent: Monday, November 2, 2015 3:34 AM
>> Cc: rkagan at virtuozzo.com; devel at linuxdriverproject.org; linux-
>> kernel at vger.kernel.org; Andrey Smetanin <asmetanin at virtuozzo.com>; KY
>> Srinivasan <kys at microsoft.com>; Haiyang Zhang
>> <haiyangz at microsoft.com>; Vitaly Kuznetsov <vkuznets at redhat.com>;
>> Denis V. Lunev <den at openvz.org>
>> Subject: [PATCH 1/1] drivers/hv: correct tsc page sequence invalid value
>>
>> From: Andrey Smetanin <asmetanin at virtuozzo.com>
>>
>> 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 that Tsc page no longer valid.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 at virtuozzo.com>
>> CC: "K. Y. Srinivasan" <kys at microsoft.com>
> Thanks Andrey; the Hyper-V team will be updating the Hyper-V documentation.
>
> Acked-by: K. Y. Srinivasan <kys at microsoft.com>
>
> Regards,
>
> K. Y
K.Y.,
can you pls clarify the state of this patch? It is a bit unclear
to me whether it is applied or not.
By the way, I also do not see the following patch
"drivers/hv: cleanup synic msrs if vmbus connect failed"
as applied in the Linux-next. You have promised to resend
it will correct author.
Thank you in advance,
Den
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