From: David Woodhouse <dwmw2@infradead.org>
To: Joao Martins <joao.m.martins@oracle.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Ankur Arora <ankur.a.arora@oracle.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Sean Christopherson <seanjc@google.com>,
kvm@vger.kernel.org
Subject: Re: [PATCH 03/15] KVM: x86/xen: intercept xen hypercalls if enabled
Date: Sat, 05 Dec 2020 18:51:08 +0000 [thread overview]
Message-ID: <9A93D396-9C77-4E57-A7E0-61BBEEB83658@infradead.org> (raw)
In-Reply-To: <e62dd528-2bee-9e8b-c395-256e6980307e@oracle.com>
On 5 December 2020 18:42:53 GMT, Joao Martins <joao.m.martins@oracle.com> wrote:
>On 12/4/20 1:18 AM, David Woodhouse wrote:
>> @@ -3742,6 +3716,9 @@ int kvm_vm_ioctl_check_extension(struct kvm
>*kvm, long ext)
>> case KVM_CAP_ENFORCE_PV_FEATURE_CPUID:
>> r = 1;
>> break;
>> + case KVM_CAP_XEN_HVM:
>> + r = 1 | KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL;
>> + break;
>
>Maybe:
>
> r = KVM_XEN_HVM_CONFIG_HYPERCALL_MSR |
> KVM_XEN_HVM_CONFIG_INTERCEPT_HCALL;
Yeah, I already did that as I did the docs. In my tree it's already folded into this patch for when I post v2. Thanks.
>I suppose it makes sense restricting to INTERCEPT_HCALL to make sure
>that the kernel only
>forwards the hcall if it is control off what it put there in the
>hypercall page (i.e.
>vmmcall/vmcall). hcall userspace exiting without INTERCEPT_HCALL would
>break ABI over how
>this ioctl was used before the new flag... In case
>kvm_xen_hypercall_enabled() would
>return true with KVM_XEN_HVM_CONFIG_HYPERCALL_MSR, as now it needs to
>handle a new
>userspace exit.
Right.
>If we're are being pedantic, the Xen hypercall MSR is a utility more
>than a necessity as
>the OS can always do without the hcall msr IIUC. But it is defacto used
>by enlightened Xen
>guests included FreeBSD.
Not sure about that. Xen doesn't guarantee that the hypercall will be VMCALL; the ABI *is* ",use the hypercall page MSR and call it" I believe.
But if they do just do the VMCALL, that *will* work as I have it, won't it?
>
>And adding:
>
>#define KVM_XEN_HVM_CONFIG_HYPERCALL_MSR (1 << 0)
>
>Of course, this is a nit for readability only, but it aligns with what
>you write
>in the docs update you do in the last patch.
Yep, already there. Thanks.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
next prev parent reply other threads:[~2020-12-05 18:52 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-04 1:18 [PATCH 00/15] KVM: Add Xen hypercall and shared info pages David Woodhouse
2020-12-04 1:18 ` [PATCH 01/15] KVM: Fix arguments to kvm_{un,}map_gfn() David Woodhouse
2020-12-04 18:27 ` Alexander Graf
2020-12-04 19:02 ` David Woodhouse
2020-12-04 1:18 ` [PATCH 02/15] KVM: x86/xen: fix Xen hypercall page msr handling David Woodhouse
2020-12-04 18:26 ` Alexander Graf
2020-12-04 18:54 ` David Woodhouse
2020-12-04 1:18 ` [PATCH 03/15] KVM: x86/xen: intercept xen hypercalls if enabled David Woodhouse
2020-12-04 18:26 ` Alexander Graf
2020-12-04 18:58 ` David Woodhouse
2020-12-05 18:42 ` Joao Martins
2020-12-05 18:51 ` David Woodhouse [this message]
2020-12-05 19:13 ` Joao Martins
2020-12-04 1:18 ` [PATCH 04/15] KVM: x86/xen: Fix coexistence of Xen and Hyper-V hypercalls David Woodhouse
2020-12-04 18:34 ` Alexander Graf
2020-12-04 19:04 ` David Woodhouse
2020-12-04 1:18 ` [PATCH 05/15] KVM: x86/xen: add KVM_XEN_HVM_SET_ATTR/KVM_XEN_HVM_GET_ATTR David Woodhouse
2020-12-04 1:18 ` [PATCH 06/15] KVM: x86/xen: latch long_mode when hypercall page is set up David Woodhouse
2020-12-04 18:38 ` Alexander Graf
2020-12-04 19:08 ` David Woodhouse
2020-12-04 1:18 ` [PATCH 07/15] KVM: x86/xen: add definitions of compat_shared_info, compat_vcpu_info David Woodhouse
2020-12-05 18:43 ` Joao Martins
2020-12-05 19:48 ` David Woodhouse
2020-12-04 1:18 ` [PATCH 08/15] KVM: x86/xen: register shared_info page David Woodhouse
2020-12-04 1:18 ` [PATCH 09/15] KVM: x86/xen: setup pvclock updates David Woodhouse
2020-12-04 1:18 ` [PATCH 10/15] xen: add wc_sec_hi to struct shared_info David Woodhouse
2020-12-04 1:18 ` [PATCH 11/15] KVM: x86/xen: update wallclock region David Woodhouse
2020-12-04 1:18 ` [PATCH 12/15] KVM: x86/xen: register vcpu info David Woodhouse
2020-12-04 1:18 ` [PATCH 13/15] KVM: x86/xen: register vcpu time info region David Woodhouse
2020-12-04 1:18 ` [PATCH 14/15] KVM: x86/xen: register runstate info David Woodhouse
2020-12-04 1:18 ` [PATCH 15/15] KVM: x86: declare Xen HVM shared info capability and add test case David Woodhouse
2020-12-04 9:11 ` [PATCH 16/15] KVM: Add documentation for Xen hypercall and shared_info updates David Woodhouse
2020-12-05 10:48 ` [PATCH 00/15] KVM: Add Xen hypercall and shared info pages David Woodhouse
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