| Message ID | 20240215235405.368539-4-amoorthy@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Improve KVM + userfaultfd performance via KVM_EXIT_MEMORY_FAULTs on stage-2 faults | expand |
On Thu, Feb 15, 2024, Anish Moorthy wrote: > This ioctl allows the user to create, modify or delete a guest physical > memory slot. Bits 0-15 of "slot" specify the slot id and this value > @@ -1382,12 +1383,16 @@ It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr > be identical. This allows large pages in the guest to be backed by large > pages in the host. > > -The flags field supports two flags: KVM_MEM_LOG_DIRTY_PAGES and > -KVM_MEM_READONLY. The former can be set to instruct KVM to keep track of > +The flags field supports three flags > + > +1. KVM_MEM_LOG_DIRTY_PAGES: can be set to instruct KVM to keep track of > writes to memory within the slot. See KVM_GET_DIRTY_LOG ioctl to know how to This formatting is funky. I suspect you are trying to avoid touching lines that otherwise wouldn't be modified, but the end result is hard to read. I would also opportunistically clean up the wording in general, e.g. 1. KVM_MEM_LOG_DIRTY_PAGES: can be set to instruct KVM to keep track of writes to memory within the slot. See KVM_GET_DIRTY_LOG ioctl for details. > -use it. The latter can be set, if KVM_CAP_READONLY_MEM capability allows it, > +use it. > +2. KVM_MEM_READONLY: can be set, if KVM_CAP_READONLY_MEM capability allows it, > to make a new slot read-only. In this case, writes to this memory will be > posted to userspace as KVM_EXIT_MMIO exits. > +3. KVM_MEM_GUEST_MEMFD: see KVM_SET_USER_MEMORY_REGION2. This flag is > +incompatible with KVM_SET_USER_MEMORY_REGION. This is now stale, as KVM_MEM_GUEST_MEMFD is also incompatible with READONLY.
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 3ec0b7a455a0..8f75fca2294e 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -1352,6 +1352,7 @@ yet and must be cleared on entry. /* for kvm_userspace_memory_region::flags */ #define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0) #define KVM_MEM_READONLY (1UL << 1) + #define KVM_MEM_GUEST_MEMFD (1UL << 2) This ioctl allows the user to create, modify or delete a guest physical memory slot. Bits 0-15 of "slot" specify the slot id and this value @@ -1382,12 +1383,16 @@ It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr be identical. This allows large pages in the guest to be backed by large pages in the host. -The flags field supports two flags: KVM_MEM_LOG_DIRTY_PAGES and -KVM_MEM_READONLY. The former can be set to instruct KVM to keep track of +The flags field supports three flags + +1. KVM_MEM_LOG_DIRTY_PAGES: can be set to instruct KVM to keep track of writes to memory within the slot. See KVM_GET_DIRTY_LOG ioctl to know how to -use it. The latter can be set, if KVM_CAP_READONLY_MEM capability allows it, +use it. +2. KVM_MEM_READONLY: can be set, if KVM_CAP_READONLY_MEM capability allows it, to make a new slot read-only. In this case, writes to this memory will be posted to userspace as KVM_EXIT_MMIO exits. +3. KVM_MEM_GUEST_MEMFD: see KVM_SET_USER_MEMORY_REGION2. This flag is +incompatible with KVM_SET_USER_MEMORY_REGION. When the KVM_CAP_SYNC_MMU capability is available, changes in the backing of the memory region are automatically reflected into the guest. For example, an
The documentation for KVM_SET_USER_MEMORY_REGION2 describes what the flag does, but the flag itself is absent from where the other memslot flags are listed. Add it. Signed-off-by: Anish Moorthy <amoorthy@google.com> --- Documentation/virt/kvm/api.rst | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)