linux-kernel - Re: [PATCH 1/1] drivers/hv: correct tsc page sequence invalid value

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Date:	Thu, 12 Nov 2015 21:57:39 +0300
From:	"Denis V. Lunev" <den@...nvz.org>
To:	KY Srinivasan <kys@...rosoft.com>
CC:	"rkagan@...tuozzo.com" <rkagan@...tuozzo.com>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrey Smetanin <asmetanin@...tuozzo.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH 1/1] drivers/hv: correct tsc page sequence invalid value

On 11/12/2015 08:35 PM, KY Srinivasan wrote:
>
>> -----Original Message-----
>> From: Denis V. Lunev [mailto:den@...nvz.org]
>> Sent: Wednesday, November 11, 2015 11:16 PM
>> To: KY Srinivasan <kys@...rosoft.com>
>> Cc: rkagan@...tuozzo.com; devel@...uxdriverproject.org; linux-
>> kernel@...r.kernel.org; Andrey Smetanin <asmetanin@...tuozzo.com>;
>> Haiyang Zhang <haiyangz@...rosoft.com>; Vitaly Kuznetsov
>> <vkuznets@...hat.com>
>> Subject: Re: [PATCH 1/1] drivers/hv: correct tsc page sequence invalid value
>>
>> On 11/02/2015 10:42 PM, KY Srinivasan wrote:
>>>> -----Original Message-----
>>>> From: Denis V. Lunev [mailto:den@...nvz.org]
>>>> Sent: Monday, November 2, 2015 3:34 AM
>>>> Cc: rkagan@...tuozzo.com; devel@...uxdriverproject.org; linux-
>>>> kernel@...r.kernel.org; Andrey Smetanin <asmetanin@...tuozzo.com>;
>> KY
>>>> Srinivasan <kys@...rosoft.com>; Haiyang Zhang
>>>> <haiyangz@...rosoft.com>; Vitaly Kuznetsov <vkuznets@...hat.com>;
>>>> Denis V. Lunev <den@...nvz.org>
>>>> Subject: [PATCH 1/1] drivers/hv: correct tsc page sequence invalid value
>>>>
>>>> From: Andrey Smetanin <asmetanin@...tuozzo.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 that Tsc page no longer valid.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@...tuozzo.com>
>>>> CC: "K. Y. Srinivasan" <kys@...rosoft.com>
>>> Thanks Andrey; the Hyper-V team will be updating the Hyper-V
>> documentation.
>>> Acked-by: K. Y. Srinivasan <kys@...rosoft.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.
> I will be submitting this shortly.
>
>> 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.
> It was resent on October 29. It is in Greg's queue.
>
> Regards,
>
> K. Y
>> Thank you in advance,
>>       Den
thank you very much for this update :)

Den
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