Messages in this thread | | | Date | Mon, 11 Dec 2023 14:57:00 -0800 | Subject | Re: [PATCH v3 1/5] KVM: Add arch specific interfaces for sampling guest callchains | From | Sean Christopherson <> |
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On Sun, Dec 10, 2023, Marc Zyngier wrote: > On Sun, 10 Dec 2023 08:12:18 +0000, Tianyi Liu <i.pear@outlook.com> wrote: > > +bool kvm_arch_vcpu_read_virt(struct kvm_vcpu *vcpu, gva_t addr, void *dest, unsigned int length) > > +{ > > + /* TODO: implement */ > > + return false; > > +} > > I don't do it very often, but the only thing I can say about this is > *NAK*. > > You have decided to ignore the previous review comments, which is your > prerogative. However, I absolutely refuse to add half baked and > *dangerous* stuff to the arm64's version of KVM. > > If you can convince the x86 folks that they absolutely want this, fine > by me. But this need to be a buy-in interface, not something that is > required for each and every architecture to have stubs, wrongly > suggesting that extra work is needed. > > For arm64, the way to go is to have this in userspace. Which is both > easy to implement and safe. And until we have such a userspace > implementation as a baseline, I will not consider a kernel > version.
I too want more justification of why this needs to be handled in the kernel[*]. The usefulness of this is dubious for many modern setups/workloads, and outright undesirable for some, e.g. many (most?) cloud providers want to make it all but impossible to access customer data.
[*] https://lore.kernel.org/all/ZSlNsn-f1j2bB8pW@FVFF77S0Q05N.cambridge.arm.com
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