[AMD Public Use] -----Original Message----- From: Sean Christopherson <seanjc@xxxxxxxxxx> Sent: Tuesday, February 16, 2021 7:03 PM To: Kalra, Ashish <Ashish.Kalra@xxxxxxx> Cc: pbonzini@xxxxxxxxxx; tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; hpa@xxxxxxxxx; rkrcmar@xxxxxxxxxx; joro@xxxxxxxxxx; bp@xxxxxxx; Lendacky, Thomas <Thomas.Lendacky@xxxxxxx>; x86@xxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; srutherford@xxxxxxxxxx; venu.busireddy@xxxxxxxxxx; Singh, Brijesh <brijesh.singh@xxxxxxx> Subject: Re: [PATCH v10 10/16] KVM: x86: Introduce KVM_GET_SHARED_PAGES_LIST ioctl On Thu, Feb 04, 2021, Ashish Kalra wrote: > From: Brijesh Singh <brijesh.singh@xxxxxxx> > > The ioctl is used to retrieve a guest's shared pages list. >What's the performance hit to boot time if KVM_HC_PAGE_ENC_STATUS is passed through to userspace? That way, userspace could manage the set of pages >in whatever data structure they want, and these get/set ioctls go away. I will be more concerned about performance hit during guest DMA I/O if the page encryption status hypercalls are passed through to user-space, a lot of guest DMA I/O dynamically sets up pages for encryption and then flips them at DMA completion, so guest I/O will surely take a performance hit with this pass-through stuff. Thanks, Ashish
