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Message-ID: <CA+EHjTyAU9XZ3OgqXjmAKh-BKsLrH_8QtnJihQxF4fhk8WPSYg@mail.gmail.com>
Date: Thu, 2 Nov 2023 14:01:39 +0000
From: Fuad Tabba <tabba@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
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"Matthew Wilcox (Oracle)" <willy@...radead.org>,
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Subject: Re: [PATCH v13 12/35] KVM: Prepare for handling only shared mappings
in mmu_notifier events
Hi,
On Fri, Oct 27, 2023 at 7:22 PM Sean Christopherson <seanjc@...gle.com> wrote:
>
> Add flags to "struct kvm_gfn_range" to let notifier events target only
> shared and only private mappings, and write up the existing mmu_notifier
> events to be shared-only (private memory is never associated with a
> userspace virtual address, i.e. can't be reached via mmu_notifiers).
>
> Add two flags so that KVM can handle the three possibilities (shared,
> private, and shared+private) without needing something like a tri-state
> enum.
>
> Link: https://lore.kernel.org/all/ZJX0hk+KpQP0KUyB@google.com
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
> include/linux/kvm_host.h | 2 ++
> virt/kvm/kvm_main.c | 7 +++++++
> 2 files changed, 9 insertions(+)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 96aa930536b1..89c1a991a3b8 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -263,6 +263,8 @@ struct kvm_gfn_range {
> gfn_t start;
> gfn_t end;
> union kvm_mmu_notifier_arg arg;
> + bool only_private;
> + bool only_shared;
If these flags aren't used in this patch series, should this patch be
moved to the other series?
Also, if shared+private is a possibility, doesn't the prefix "only_"
confuse things a bit? I.e., what is shared+private, is it when both
are 0 or when both are 1? I assume it's the former (both are 0), but
it might be clearer.
Cheers,
/fuad
> bool may_block;
> };
> bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index cb9376833c18..302ccb87b4c1 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -635,6 +635,13 @@ static __always_inline kvm_mn_ret_t __kvm_handle_hva_range(struct kvm *kvm,
> * the second or later invocation of the handler).
> */
> gfn_range.arg = range->arg;
> +
> + /*
> + * HVA-based notifications aren't relevant to private
> + * mappings as they don't have a userspace mapping.
> + */
> + gfn_range.only_private = false;
> + gfn_range.only_shared = true;
> gfn_range.may_block = range->may_block;
>
> /*
> --
> 2.42.0.820.g83a721a137-goog
>
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