From: "Michael S. Tsirkin" <mst@redhat.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Peter Xu <peterx@redhat.com>,
Julia Suvorova <jsuvorov@redhat.com>,
Andy Lutomirski <luto@kernel.org>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/3] KVM: x86: KVM_MEM_PCI_HOLE memory
Date: Thu, 6 Aug 2020 08:19:30 -0400 [thread overview]
Message-ID: <20200806081800-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <87wo2cngv6.fsf@vitty.brq.redhat.com>
On Thu, Aug 06, 2020 at 01:39:09PM +0200, Vitaly Kuznetsov wrote:
> "Michael S. Tsirkin" <mst@redhat.com> writes:
>
> > About the feature bit, I am not sure why it's really needed. A single
> > mmio access is cheaper than two io accesses anyway, right? So it makes
> > sense for a kvm guest whether host has this feature or not.
> > We need to be careful and limit to a specific QEMU implementation
> > to avoid tripping up bugs, but it seems more appropriate to
> > check it using pci host IDs.
>
> Right, it's just that "running on KVM" is too coarse grained, we just
> need a way to somehow distinguish between "known/good" and
> "unknown/buggy" configurations.
Basically it's not KVM, it's QEMU that is known good. QEMU vendor id in
the pci host seems like a reasonable way to detect that. If someone
reuses QEMU ID - I guess they better behave just like QEMU :)
I also proposed only limiting this to register 0 (device id),
will make it very unlikely this can break accidentally ...
> --
> Vitaly
prev parent reply other threads:[~2020-08-06 16:58 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-28 14:37 [PATCH 0/3] KVM: x86: KVM_MEM_PCI_HOLE memory Vitaly Kuznetsov
2020-07-28 14:37 ` [PATCH 1/3] KVM: x86: move kvm_vcpu_gfn_to_memslot() out of try_async_pf() Vitaly Kuznetsov
2020-07-28 14:37 ` [PATCH 2/3] KVM: x86: introduce KVM_MEM_PCI_HOLE memory Vitaly Kuznetsov
2020-08-05 15:18 ` Andrew Jones
2020-08-06 9:08 ` Vitaly Kuznetsov
2020-08-05 17:05 ` Jim Mattson
2020-08-06 0:18 ` Michael S. Tsirkin
2020-08-06 17:36 ` Jim Mattson
2020-08-06 9:14 ` Vitaly Kuznetsov
2020-07-28 14:37 ` [PATCH 3/3] KVM: selftests: add KVM_MEM_PCI_HOLE test Vitaly Kuznetsov
2020-08-06 0:21 ` [PATCH 0/3] KVM: x86: KVM_MEM_PCI_HOLE memory Michael S. Tsirkin
2020-08-06 9:19 ` Vitaly Kuznetsov
2020-08-06 9:53 ` Michael S. Tsirkin
2020-08-06 11:39 ` Vitaly Kuznetsov
2020-08-06 12:19 ` Michael S. Tsirkin [this message]
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