> -----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 that Tsc page no longer valid.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 > 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@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> Regards, K. Y > CC: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx> > CC: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> > > TARGET: Microsoft Hyper-V Linux guest drivers > Signed-off-by: Denis V. Lunev <den@xxxxxxxxxx> > --- > drivers/hv/hv.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c > index 6341be8..68d0701 100644 > --- a/drivers/hv/hv.c > +++ b/drivers/hv/hv.c > @@ -139,7 +139,7 @@ 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. > */ > @@ -161,7 +161,7 @@ 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. > -- > 2.1.4 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
