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Re: [Qemu-devel] [PATCH v8 2/9] icount: exit cpu loop on expire
From: |
Pavel Dovgalyuk |
Subject: |
Re: [Qemu-devel] [PATCH v8 2/9] icount: exit cpu loop on expire |
Date: |
Thu, 26 Jan 2017 17:32:37 +0300 |
> From: Paolo Bonzini [mailto:address@hidden
> On 26/01/2017 14:37, Pavel Dovgalyuk wrote:
> >> Simpler:
> >>
> >> use_icount &&
> >> ((int32_t)cpu->icount_decr.u32 < 0 ||
> >> cpu->icount_decr.u16.low + cpu->icount_extra == 0)
> > Right.
> >
> >> But I'm not sure that you need to test u32. After all you're not
> > Checking u32 is needed, because sometimes it is less than zero.
>
> If cpu->icount_decr.u32 is less than zero, the next translation block
> would immediately exit with TB_EXIT_ICOUNT_EXPIRED, causing
>
> cpu->exception_index = EXCP_INTERRUPT;
> *last_tb = NULL;
> cpu_loop_exit(cpu);
>
> from cpu_loop_exec_tb's "case TB_EXIT_ICOUNT_EXPIRED".
>
> And the same is true for cpu->icount_decr.u16.low + cpu->icount_extra ==
> 0, so I don't understand why this part of the patch is necessary.
I removed that lines because we have to check icount=0 not only when it is
expired,
but also when all instructions were executed successfully.
If there are no instructions to execute, calling tb_find (and translation then)
may cause an exception at the wrong moment.
Pavel Dovgalyuk
- [Qemu-devel] [PATCH v8 0/9] replay additions, Pavel Dovgalyuk, 2017/01/26
- [Qemu-devel] [PATCH v8 1/9] replay: exception replay fix, Pavel Dovgalyuk, 2017/01/26
- [Qemu-devel] [PATCH v8 2/9] icount: exit cpu loop on expire, Pavel Dovgalyuk, 2017/01/26
- Re: [Qemu-devel] [PATCH v8 2/9] icount: exit cpu loop on expire, Paolo Bonzini, 2017/01/26
- Re: [Qemu-devel] [PATCH v8 2/9] icount: exit cpu loop on expire, Pavel Dovgalyuk, 2017/01/26
- Re: [Qemu-devel] [PATCH v8 2/9] icount: exit cpu loop on expire, Paolo Bonzini, 2017/01/26
- Re: [Qemu-devel] [PATCH v8 2/9] icount: exit cpu loop on expire,
Pavel Dovgalyuk <=
- Re: [Qemu-devel] [PATCH v8 2/9] icount: exit cpu loop on expire, Paolo Bonzini, 2017/01/26
- Re: [Qemu-devel] [PATCH v8 2/9] icount: exit cpu loop on expire, Pavel Dovgalyuk, 2017/01/27
- Re: [Qemu-devel] [PATCH v8 2/9] icount: exit cpu loop on expire, Paolo Bonzini, 2017/01/27
[Qemu-devel] [PATCH v8 3/9] apic: save apic_delivered flag, Pavel Dovgalyuk, 2017/01/26
[Qemu-devel] [PATCH v8 4/9] integratorcp: adding vmstate for save/restore, Pavel Dovgalyuk, 2017/01/26
[Qemu-devel] [PATCH v8 5/9] block: implement bdrv_snapshot_goto for blkreplay, Pavel Dovgalyuk, 2017/01/26