| Message ID | 20231027182217.3615211-13-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: guest_memfd() and per-page attributes | expand |
On 10/27/23 20:21, Sean Christopherson wrote: > @@ -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. It's confusing who "they" is. Maybe * HVA-based notifications provide a userspace address, * and as such are only relevant for shared mappings. Paolo > + */ > + gfn_range.only_private = false; > + gfn_range.only_shared = true; > gfn_range.may_block = range->may_block; > > /*
On Mon, Oct 30, 2023, Paolo Bonzini wrote: > On 10/27/23 20:21, Sean Christopherson wrote: > > @@ -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. > > It's confusing who "they" is. Maybe > > * HVA-based notifications provide a userspace address, > * and as such are only relevant for shared mappings. Works for me.
On 10/28/2023 2:21 AM, Sean Christopherson 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. I see the two flags are set/cleared in __kvm_handle_hva_range() in this patch and kvm_handle_gfn_range() from the later patch 13/35, but I didn't see they are used/read in this patch series if I didn't miss anything. How are they supposed to be used in KVM? > > Link: https://lore.kernel.org/all/ZJX0hk+KpQP0KUyB@google.com > Signed-off-by: Sean Christopherson <seanjc@google.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; > 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; > > /*
On 11/2/23 06:59, Binbin Wu 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. > > I see the two flags are set/cleared in __kvm_handle_hva_range() in > this patch and kvm_handle_gfn_range() from the later patch 13/35, but > I didn't see they are used/read in this patch series if I didn't miss > anything. How are they supposed to be used in KVM? They are going to be used by SNP/TDX patches. Paolo
Hi, On Fri, Oct 27, 2023 at 7:22 PM Sean Christopherson <seanjc@google.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@google.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 >
On Thu, Nov 02, 2023, Fuad Tabba wrote: > Hi, > > On Fri, Oct 27, 2023 at 7:22 PM Sean Christopherson <seanjc@google.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@google.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? If *both* TDX and SNP need this patch, then I think it's probably worth applying it now to make their lives easier. But if only one needs the support, then I completely agree this should be punted to whichever series needs it (this also came up in v11, but we didn't force the issue). Mike, Isaku? > 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. Heh, I was hoping that "only_private && only_shared" would be obviously nonsensical. The only alternative I can think would be to add an enum, e.g. enum { PROCESS_PRIVATE_AND_SHARED, PROCESS_ONLY_PRIVATE, PROCESS_ONLY_SHARED, }; because every other way of expressing the flags either results in more confusion or an unsafe default. I.e. I want zapping only private or only shared to require the caller to explicitly set a non-zero value, which is how I ended up with "only_{private,shared}" as opposed to "process_{private,shared}".
On Thu, Nov 2, 2023 at 2:41 PM Sean Christopherson <seanjc@google.com> wrote: > > On Thu, Nov 02, 2023, Fuad Tabba wrote: > > Hi, > > > > On Fri, Oct 27, 2023 at 7:22 PM Sean Christopherson <seanjc@google.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@google.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? > > If *both* TDX and SNP need this patch, then I think it's probably worth applying > it now to make their lives easier. But if only one needs the support, then I > completely agree this should be punted to whichever series needs it (this also > came up in v11, but we didn't force the issue). > > Mike, Isaku? > > > 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. > > Heh, I was hoping that "only_private && only_shared" would be obviously nonsensical. > > The only alternative I can think would be to add an enum, e.g. > > enum { > PROCESS_PRIVATE_AND_SHARED, > PROCESS_ONLY_PRIVATE, > PROCESS_ONLY_SHARED, > }; > > because every other way of expressing the flags either results in more confusion > or an unsafe default. I.e. I want zapping only private or only shared to require > the caller to explicitly set a non-zero value, which is how I ended up with > "only_{private,shared}" as opposed to "process_{private,shared}". I don't have a strong opinion about this. Having an enum looks good to me. Cheers, /fuad
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; 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; /*
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@google.com> --- include/linux/kvm_host.h | 2 ++ virt/kvm/kvm_main.c | 7 +++++++ 2 files changed, 9 insertions(+)