Messages in this thread | | | Subject | Re: [PATCH 2/7] powerpc/watchpoint/kvm: Add infrastructure to support 2nd DAWR | From | Ravi Bangoria <> | Date | Wed, 2 Sep 2020 10:39:06 +0530 |
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Hi Paul,
On 9/2/20 7:31 AM, Paul Mackerras wrote: > On Thu, Jul 23, 2020 at 03:50:53PM +0530, Ravi Bangoria wrote: >> kvm code assumes single DAWR everywhere. Add code to support 2nd DAWR. >> DAWR is a hypervisor resource and thus H_SET_MODE hcall is used to set/ >> unset it. Introduce new case H_SET_MODE_RESOURCE_SET_DAWR1 for 2nd DAWR. > > Is this the same interface as will be defined in PAPR and available > under PowerVM, or is it a new/different interface for KVM?
Yes, kvm hcall interface for 2nd DAWR is same as PowerVM, as defined in PAPR.
> >> Also, kvm will support 2nd DAWR only if CPU_FTR_DAWR1 is set. > > In general QEMU wants to be able to control all aspects of the virtual > machine presented to the guest, meaning that just because a host has a > particular hardware capability does not mean we should automatically > present that capability to the guest. > > In this case, QEMU will want a way to control whether the guest sees > the availability of the second DAWR/X registers or not, i.e. whether a > H_SET_MODE to set DAWR[X]1 will succeed or fail.
Patch #3 adds new kvm capability KVM_CAP_PPC_DAWR1 that can be checked by Qemu. Also, as suggested by David in Qemu patch[1], I'm planning to add new machine capability in Qemu:
-machine cap-dawr1=ON/OFF
cap-dawr1 will be default ON when PPC_FEATURE2_ARCH_3_10 is set and OFF otherwise.
Is this correct approach?
[1]: https://lore.kernel.org/kvm/20200724045613.GA8983@umbus.fritz.box
Thanks, Ravi
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