Messages in this thread | | | Date | Thu, 2 Nov 2023 10:19:50 +0800 | Subject | Re: [PATCH v13 09/35] KVM: Add KVM_EXIT_MEMORY_FAULT exit to report faults to userspace | From | Xiaoyao Li <> |
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On 11/2/2023 1:36 AM, Sean Christopherson wrote: >> KVM_CAP_MEMORY_FAULT_INFO is x86 only, is it better to put this function to >> <asm/kvm_host.h>? > I'd prefer to keep it in generic code, as it's highly likely to end up there > sooner than later. There's a known use case for ARM (exit to userspace on missing > userspace mapping[*]), and I'm guessing pKVM (also ARM) will also utilize this API. > > [*]https://lore.kernel.org/all/20230908222905.1321305-8-amoorthy@google.com
I wonder how this CAP is supposed to be checked in userspace, for guest memfd case? something like this?
if (!kvm_check_extension(s, KVM_CAP_MEMORY_FAULT_INFO) && run->exit_reason == KVM_EXIT_MEMORY_FAULT) abort("unexpected KVM_EXIT_MEMORY_FAULT");
In my implementation of QEMU patches, I find it's unnecessary. When userspace gets an exit with KVM_EXIT_MEMORY_FAULT, it implies "KVM_CAP_MEMORY_FAULT_INFO".
So I don't see how it is necessary in this series. Whether it's necessary or not for [*], I don't have the answer but we can leave the discussion to that patch series.
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