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Message-ID: <ZLlLx7wkE6iPTIcI@google.com>
Date: Thu, 20 Jul 2023 08:14:47 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Xiaoyao Li <xiaoyao.li@...el.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Marc Zyngier <maz@...nel.org>,
Oliver Upton <oliver.upton@...ux.dev>,
Huacai Chen <chenhuacai@...nel.org>,
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Albert Ou <aou@...s.berkeley.edu>,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
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James Morris <jmorris@...ei.org>,
"Serge E. Hallyn" <serge@...lyn.com>, kvm@...r.kernel.org,
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Isaku Yamahata <isaku.yamahata@...il.com>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFC PATCH v11 12/29] KVM: Add KVM_CREATE_GUEST_MEMFD ioctl() for
guest-specific backing memory
On Thu, Jul 20, 2023, Xiaoyao Li wrote:
> On 7/19/2023 7:44 AM, Sean Christopherson wrote:
> > @@ -5134,6 +5167,16 @@ static long kvm_vm_ioctl(struct file *filp,
> > case KVM_GET_STATS_FD:
> > r = kvm_vm_ioctl_get_stats_fd(kvm);
> > break;
> > + case KVM_CREATE_GUEST_MEMFD: {
> > + struct kvm_create_guest_memfd guest_memfd;
> > +
> > + r = -EFAULT;
> > + if (copy_from_user(&guest_memfd, argp, sizeof(guest_memfd)))
> > + goto out;
> > +
> > + r = kvm_gmem_create(kvm, &guest_memfd);
> > + break;
> > + }
>
> Does it need a new CAP to indicate the support of guest_memfd?
Yeah, I meant to add that to the TODO list and forgot (obviously).
> This is patch series introduces 3 new CAPs and it seems any one of them can
> serve as the indicator of guest_memfd.
>
> +#define KVM_CAP_USER_MEMORY2 230
> +#define KVM_CAP_MEMORY_ATTRIBUTES 231
> +#define KVM_CAP_VM_TYPES 232
The number of new caps being added is the main why I didn't just add another one.
On the other hand, we have room for a few billion caps, so one more isn't a big
deal. So yeah, KVM_CAP_GUEST_MEMFD is probably the way to go.
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