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

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Date:	Thu, 12 Nov 2015 17:35:20 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	"Denis V. Lunev" <den@...nvz.org>
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



> -----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 that Tsc page no longer valid.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
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