Re: [Xen-devel] [PATCH 06/13] x86/hvm: Scale host TSC when setting/getting guest TSC

[Haozhong Zhang <haozhong.zhang@xxxxxxxxx>]

On Tue, Oct 27, 2015 at 02:15:53AM -0600, Jan Beulich wrote:
> >>> On 27.10.15 at 02:54, <haozhong.zhang@xxxxxxxxx> wrote:
> > On Thu, Oct 22, 2015 at 08:17:29AM -0600, Jan Beulich wrote:
> >> >>> On 28.09.15 at 09:13, <haozhong.zhang@xxxxxxxxx> wrote:
> >> > The existing hvm_set_guest_tsc_fixed() and hvm_get_guest_tsc_fixed()
> >> > calculate the guest TSC by adding the TSC offset to the host TSC. When
> >> > the TSC scaling is enabled, the host TSC should be scaled first. This
> >> > patch adds the scaling logic to those two functions.
> >> 
> >> Just like mentioned for the first twp patches - I'd first of all like to
> >> understand why the lack of scaling this wasn't an issue for SVM so
> >> far. What you reads plausible, but assuming that SVM TSC scaling
> >> code was tested, I'm hesitant to apply changes to it without
> >> understanding the details (or at least without SVM maintainers'
> >> consent).
> >>
> > 
> > The current SVM TSC ratio code does not seem correct w/o patch 6 (as
> > well as patch 2, but I only analyze patch 6 here). Following is the
> > explanation.
> 
> Right - as said before, all you write reads plausible, but will need
> confirming by an SVM maintainer. And then I'd like to ask you to
> re-order you patch series to fix bugs first (whether that's along
> with generalizing or ahead of it I'd leave to you, as long as the
> result meets the main goal I'm having here: backportability).
> 
> Jan
>

I'll wait for SVM maintainers' comments. If this patch 6 is valid,
I'll put all bug fixes to the beginning in the next version.

Thanks,
Haozhong

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