On Tue, 25 Oct 2022 at 16:21, Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> wrote: > > This new KVM exit allows userspace to handle memory-related errors. It > indicates an error happens in KVM at guest memory range [gpa, gpa+size). > The flags includes additional information for userspace to handle the > error. Currently bit 0 is defined as 'private memory' where '1' > indicates error happens due to private memory access and '0' indicates > error happens due to shared memory access. > > When private memory is enabled, this new exit will be used for KVM to > exit to userspace for shared <-> private memory conversion in memory > encryption usage. In such usage, typically there are two kind of memory > conversions: > - explicit conversion: happens when guest explicitly calls into KVM > to map a range (as private or shared), KVM then exits to userspace > to perform the map/unmap operations. > - implicit conversion: happens in KVM page fault handler where KVM > exits to userspace for an implicit conversion when the page is in a > different state than requested (private or shared). > > Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx> > Co-developed-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx> > Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx> > Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx> > --- > Documentation/virt/kvm/api.rst | 23 +++++++++++++++++++++++ > include/uapi/linux/kvm.h | 9 +++++++++ > 2 files changed, 32 insertions(+) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index f3fa75649a78..975688912b8c 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -6537,6 +6537,29 @@ array field represents return values. The userspace should update the return > values of SBI call before resuming the VCPU. For more details on RISC-V SBI > spec refer, https://github.com/riscv/riscv-sbi-doc. > > +:: > + > + /* KVM_EXIT_MEMORY_FAULT */ > + struct { > + #define KVM_MEMORY_EXIT_FLAG_PRIVATE (1 << 0) > + __u32 flags; > + __u32 padding; > + __u64 gpa; > + __u64 size; > + } memory; > + > +If exit reason is KVM_EXIT_MEMORY_FAULT then it indicates that the VCPU has > +encountered a memory error which is not handled by KVM kernel module and > +userspace may choose to handle it. The 'flags' field indicates the memory > +properties of the exit. > + > + - KVM_MEMORY_EXIT_FLAG_PRIVATE - indicates the memory error is caused by > + private memory access when the bit is set. Otherwise the memory error is > + caused by shared memory access when the bit is clear. > + > +'gpa' and 'size' indicate the memory range the error occurs at. The userspace > +may handle the error and return to KVM to retry the previous memory access. > + What's the difference between this and a plain old MMIO exit ? Just that we can specify a wider size and some flags ? -- PMM
