+Paolo On Sun, Apr 18, 2021, Sasha Levin wrote: > This is a note to let you know that I've just added the patch titled > > KVM: VMX: Convert vcpu_vmx.exit_reason to a union > > to the 5.10-stable tree which can be found at: > http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary > > The filename of the patch is: > kvm-vmx-convert-vcpu_vmx.exit_reason-to-a-union.patch > and it can be found in the queue-5.10 subdirectory. > > If you, or anyone else, feels it should not be added to the stable tree, > please let <stable@xxxxxxxxxxxxxxx> know about it. I'm not sure we want this going into stable kernels, even for 5.10 and 5.11. I assume it got pulled in to resolve a conflict with commit 04c4f2ee3f68 ("KVM: VMX: Don't use vcpu->run->internal.ndata as an array index"), but that's should be trivial to resolve since it's just a collision with surrounding code. Maybe we'll end up with a more painful conflict in the future that would be best solved by grabbing this refactoring, but I don't think we're there yet. > commit 1499b54db7d9e7e5f5014307e8391e3ad7986f1f > Author: Sean Christopherson <seanjc@xxxxxxxxxx> > Date: Fri Nov 6 17:03:12 2020 +0800 > > KVM: VMX: Convert vcpu_vmx.exit_reason to a union > > [ Upstream commit 8e53324021645f820a01bf8aa745711c802c8542 ] > > Convert vcpu_vmx.exit_reason from a u32 to a union (of size u32). The > full VM_EXIT_REASON field is comprised of a 16-bit basic exit reason in > bits 15:0, and single-bit modifiers in bits 31:16. > > Historically, KVM has only had to worry about handling the "failed > VM-Entry" modifier, which could only be set in very specific flows and > required dedicated handling. I.e. manually stripping the FAILED_VMENTRY > bit was a somewhat viable approach. But even with only a single bit to > worry about, KVM has had several bugs related to comparing a basic exit > reason against the full exit reason store in vcpu_vmx. > > Upcoming Intel features, e.g. SGX, will add new modifier bits that can > be set on more or less any VM-Exit, as opposed to the significantly more > restricted FAILED_VMENTRY, i.e. correctly handling everything in one-off > flows isn't scalable. Tracking exit reason in a union forces code to > explicitly choose between consuming the full exit reason and the basic > exit, and is a convenient way to document and access the modifiers. > > No functional change intended. > > Cc: Xiaoyao Li <xiaoyao.li@xxxxxxxxx> > Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> > Signed-off-by: Chenyi Qiang <chenyi.qiang@xxxxxxxxx> > Message-Id: <20201106090315.18606-2-chenyi.qiang@xxxxxxxxx> > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
