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

From: Denis V. Lunev
Date: Thu Nov 12 2015 - 02:16:41 EST

On 11/02/2015 10:42 PM, KY Srinivasan wrote:

-----Original Message-----
From: Denis V. Lunev [mailto:den@xxxxxxxxxx]
Sent: Monday, November 2, 2015 3:34 AM
Cc: rkagan@xxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; linux-
kernel@xxxxxxxxxxxxxxx; Andrey Smetanin <asmetanin@xxxxxxxxxxxxx>; KY
Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang
<haiyangz@xxxxxxxxxxxxx>; Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>;
Denis V. Lunev <den@xxxxxxxxxx>
Subject: [PATCH 1/1] drivers/hv: correct tsc page sequence invalid value

From: Andrey Smetanin <asmetanin@xxxxxxxxxxxxx>

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that Tsc page no longer valid.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
mov rax, cs:HvlpReferenceTscPage
mov r9d, [rax]
test r9d, r9d
jz short loc_1401C3176
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
mov ecx, 40000020h
shl rdx, 20h
or rdx, rax
mov rax, rdx
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@xxxxxxxxxxxxx>
CC: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
Thanks Andrey; the Hyper-V team will be updating the Hyper-V documentation.

Acked-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>


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,
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