Question about VM_EXIT_ACK_INTR_ON_EXIT

Question

Question about VM_EXIT_ACK_INTR_ON_EXIT

wbenny opened this issue 6 years ago · 5 comments

Hi,
is setting VM_EXIT_ACK_INTR_ON_EXIT flag really necessary, if PIN_BASED_EXT_INTR is not set? I hope it's not super stupid question, but if I understand Intel Manual correctly, you shouldn't get any VMEXITs for external interrupts when PIN_BASED_EXT_INTR is not set - and if this is the case, the VM_EXIT_ACK_INTR_ON_EXIT is unnecessary.

I'm quite confused by this - I've been stuck on the VM_EXIT_ACK_INTR_ON_EXIT flag for too long in the Intel Manual, and when I thought I understand what it does, I realised many "simple opensource hypervisors" unneccessarily set it (SimpleVisor, ksm, HyperPlatform, ...).

So now I'm wondering, if either my understanding is correct OR if everyone just blatantly copy-pasted this practice from somewhere :)

If I'm completely wrong, I would be glad if you corrected me.

Answer 1 · 2018-08-01T22:25:40.000Z

It's not needed. In Bareflank, we don't set it in the base hypervisor.
https://github.com/Bareflank/hypervisor/blob/master/bfvmm/src/hve/arch/intel_x64/exit_handler/exit_handler.cpp#L574

Answer 2 · 2018-08-01T23:12:05.000Z

Nice, thanks Rian!

Answer 3 · 2018-08-02T12:50:58.000Z

It’s not needed, you’re right. Want to do a pull request please (and test it?)

On Thu, Aug 2, 2018 at 12:12 AM Parallel Xenoexcite < ***@***.***> wrote: Nice, thanks Rian! — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#31 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AFxIeLjG10LKWt7CnBjBJSwxGTsFQaFEks5uMjXHgaJpZM4Vn1IM> .

-- Best regards, Alex Ionescu

Answer 4 · 2018-08-02T15:33:55.000Z

If testing inside of the VMWare is enough, I'll gladly provide pull request later today. :)

Answer 5 · 2018-08-02T15:35:48.000Z

Yep it’s eniugh :)

On Thu, Aug 2, 2018 at 4:35 PM Parallel Xenoexcite ***@***.***> wrote: If testing inside of the VMWare is enough, I'll gladly provide pull request later today. :) — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#31 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AFxIeOj_4sZn4WeJ3HR39M9CeNFavn-Mks5uMxw5gaJpZM4Vn1IM> .

-- Best regards, Alex Ionescu