Messages in this thread Patch in this message | | | From | "Victor Miasnikov" <> | Subject | KVM "Hyper-V emulation" -- this can be related "Linux on Hyper-V" ? Or "KVM emulates Hyper-V" as "Hyper-V emulates Hyper-V" ? Re: [PATCH 2/3] X86: Add a check to catch Xen emulation of Hyper-V | Date | Wed, 17 Apr 2013 12:10:01 +0300 |
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Hi!
Short:
>> >> When KVM runs in Hyper-V emulation mode it expects to get Hyper-V hypercalls. >> >> Mixing KVM hypercalls and Hyper-V requires some tricks. It VVM>> KVM "Hyper-V emulation" -- this can be related "Linux on Hyper-V" ? > It's not related.
Are You shue? Xen-team _think_ too what is not related, but has non-100% _full_ emulation of Hyper-V and, as result, create problems
Question is very simple: Hyper-V users/sysadmins need wait patch a-la this:
== KVM emulates Hyper-V to host enlightened Windows.
. . .
[ hpa: the problem here is that KVM doesn't emulate Hyper-V well enough, . . ]
. . .
+ * KVM emulates Hyper-V to support enlightened Windows. + * Check to see first if we are on a KVM Hypervisor. + if (KVM_cpuid_base()) + return false; . . . ==
Or "KVM emulates Hyper-V" as "Hyper-V emulates Hyper-V" ?
-- Full:
----- Original Message ----- From: "Michael S. Tsirkin" To: "K. Y. Srinivasan" Cc: Sent: Wednesday, April 17, 2013 10:06 AM Subject: Re: [PATCH 2/3] X86: Add a check to catch Xen emulation of Hyper-V
> On Sun, Feb 03, 2013 at 05:22:38PM -0800, K. Y. Srinivasan wrote: >> Xen emulates Hyper-V to host enlightened Windows. Looks like this >> emulation may be turned on by default even for Linux guests. Check and >> fail Hyper-V detection if we are on Xen. >> >> Signed-off-by: K. Y. Srinivasan kys (at) microsoft.com > > I'm very curious what's the specific bug that is fixed here? > I went over the original discussion in > https://patchwork.kernel.org/patch/2064331/ > and that's still not clear to me. Is there a configuration > that is broken without this patch but starts working with > this patch? > > It seems that one might want to use hyper-v emulation e.g. to test > hyper-v code without using windows, so the functionality > that this patch disables is not completely useless, > so there should be a good reason for disabling it. > > Could you enlighten me please? :)
Short history of question:
{{ == > > And hypercall has its own set of problems with Windows guests. > > When KVM runs in Hyper-V emulation mode it expects to get Hyper-V hypercalls. > > Mixing KVM hypercalls and Hyper-V requires some tricks. It > > Can't we simply register a hypercall ID range with Microsoft? > > > may also affect WHQLing Windows drivers since driver will talk to HW > > bypassing Windows interfaces. > > Then the WHQL'ed driver doesn't support the PV MMIO hcall? ==
KVM "Hyper-V emulation" -- this can be related "Linux on Hyper-V" ? }}
{{ >> >> When KVM runs in Hyper-V emulation mode it expects to get Hyper-V hypercalls. >> >> Mixing KVM hypercalls and Hyper-V requires some tricks. It >> KVM "Hyper-V emulation" -- this can be related "Linux on Hyper-V" ? > It's not related.
Are You shue? Xen-team _think_ too what is not related, but has non-100% _full_ emulation of Hyper-V and, as result, create problems:
== Xen emulates Hyper-V to host enlightened Windows. Looks like this emulation may be turned on by default even for Linux guests. Check and fail Hyper-V detection if we are on Xen.
[ hpa: the problem here is that Xen doesn't emulate Hyper-V well enough, and if the Xen support isn't compiled in, we end up stubling over the Hyper-V emulation and try to activate it -- and it fails. ]
. . .
+ /* + * Xen emulates Hyper-V to support enlightened Windows. + * Check to see first if we are on a Xen Hypervisor. + */ + if (xen_cpuid_base()) + return false; + == }}
Question is very simple: Hyper-V users/sysadmins need wait patch a-la this:
== KVM emulates Hyper-V to host enlightened Windows. Looks like this emulation may be turned on by default even for Linux guests. Check and fail Hyper-V detection if we are on KVM.
[ hpa: the problem here is that KVM doesn't emulate Hyper-V well enough, and if the KVM support isn't compiled in, we end up stubling over the Hyper-V emulation and try to activate it -- and it fails. ]
. . .
+ /* + * KVM emulates Hyper-V to support enlightened Windows. + * Check to see first if we are on a KVM Hypervisor. + */ + if (KVM_cpuid_base()) + return false; + ==
Or "KVM emulates Hyper-V" as "Hyper-V emulates Hyper-V" ?
Best regards, Victor Miasnikov Blog: http://vvm.blog.tut.by/
P.S.
----- Original Message ----- From: "Michael S. Tsirkin" To: "Victor Miasnikov" Sent: Wednesday, April 17, 2013 10:07 AM
I'm not sure what are we talking about then, but please use the mailing list appropriate for the subject.
----- Original Message ----- From: "Victor Miasnikov" vvm (a) tut (dot) by To: "Michael S. Tsirkin" Cc: "KY Srinivasan" Sent: Tuesday, April 16, 2013 9:36 AM Subject: Are You shue what is 100% _full_ emulation of Hyper-V? Re: It's not related Re: KVM "Hyper-V emulation" -- this can be related "Linux on Hyper-V" ?
Hi!
>> >> When KVM runs in Hyper-V emulation mode it expects to get Hyper-V hypercalls. >> >> Mixing KVM hypercalls and Hyper-V requires some tricks. It >> KVM "Hyper-V emulation" -- this can be related "Linux on Hyper-V" ? > It's not related.
Are You shue? Xen-team _think_ too what is not related, but has non-100% _full_ emulation of Hyper-V and, as result, create problems:
== Xen emulates Hyper-V to host enlightened Windows. Looks like this emulation may be turned on by default even for Linux guests. Check and fail Hyper-V detection if we are on Xen.
[ hpa: the problem here is that Xen doesn't emulate Hyper-V well enough, and if the Xen support isn't compiled in, we end up stubling over the Hyper-V emulation and try to activate it -- and it fails. ]
. . .
+ /* + * Xen emulates Hyper-V to support enlightened Windows. + * Check to see first if we are on a Xen Hypervisor. + */ + if (xen_cpuid_base()) + return false; + ==
( full see ib P.S.)
Best regards, Victor Miasnikov Blog: http://vvm.blog.tut.by/
P.S.
== ----- Original Message ----- From: "tip-bot for K. Y. Srinivasan"
. . .
Sent: Wednesday, February 13, 2013 3:57 AM Subject: [tip:x86/hyperv] X86: Add a check to catch Xen emulation of Hyper-V
Commit-ID: db34bbb767bdfa1ebed7214b876fe01c5b7ee457 Gitweb: http://git.kernel.org/tip/db34bbb767bdfa1ebed7214b876fe01c5b7ee457 Author: K. Y. Srinivasan AuthorDate: Sun, 3 Feb 2013 17:22:38 -0800 Committer: H. Peter Anvin CommitDate: Tue, 12 Feb 2013 16:27:03 -0800
X86: Add a check to catch Xen emulation of Hyper-V
Xen emulates Hyper-V to host enlightened Windows. Looks like this emulation may be turned on by default even for Linux guests. Check and fail Hyper-V detection if we are on Xen.
[ hpa: the problem here is that Xen doesn't emulate Hyper-V well enough, and if the Xen support isn't compiled in, we end up stubling over the Hyper-V emulation and try to activate it -- and it fails. ]
Signed-off-by: K. Y. Srinivasan Link: http://lkml.kernel.org/r/1359940959-32168-2-git-send-email-kys@microsoft.com Signed-off-by: H. Peter Anvin --- arch/x86/kernel/cpu/mshyperv.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index 646d192..4dab317 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -30,6 +30,13 @@ static bool __init ms_hyperv_platform(void) if (!boot_cpu_has(X86_FEATURE_HYPERVISOR)) return false;
+ /* + * Xen emulates Hyper-V to support enlightened Windows. + * Check to see first if we are on a Xen Hypervisor. + */ + if (xen_cpuid_base()) + return false; + cpuid(HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS, &eax, &hyp_signature[0], &hyp_signature[1], &hyp_signature[2]);
-- ==
----- Original Message ----- From: "Michael S. Tsirkin" To: "Victor Miasnikov" vvm (a) tut (dot) by Sent: Tuesday, April 16, 2013 1:11 AM Subject: Re: KVM "Hyper-V emulation" -- this can be related "Linux on Hyper-V" ? Fw: When KVM runs in Hyper-V emulation mode it expects to get Hyper-V hypercalls.
> On Mon, Apr 15, 2013 at 04:00:34PM +0300, Victor Miasnikov wrote: >> >> == >> >> And hypercall has its own set of problems with Windows guests. >> >> When KVM runs in Hyper-V emulation mode it expects to get Hyper-V hypercalls. >> >> Mixing KVM hypercalls and Hyper-V requires some tricks. It >> > >> >Can't we simply register a hypercall ID range with Microsoft? >> > >> >> may also affect WHQLing Windows drivers since driver will talk to HW >> >> bypassing Windows interfaces. >> > >> >Then the WHQL'ed driver doesn't support the PV MMIO hcall? >> == >> >> KVM "Hyper-V emulation" -- this can be related "Linux on Hyper-V" ? >> >> > > It's not related.
----- Original Message ----- From: "Victor Miasnikov" vvm (a) tut (dot) by To: "Michael S. Tsirkin" Sent: Monday, April 15, 2013 4:00 PM Subject: KVM "Hyper-V emulation" -- this can be related "Linux on Hyper-V" ? Fw: When KVM runs in Hyper-V emulation mode it expects to get Hyper-V hypercalls.
Hi!
== > > And hypercall has its own set of problems with Windows guests. > > When KVM runs in Hyper-V emulation mode it expects to get Hyper-V hypercalls. > > Mixing KVM hypercalls and Hyper-V requires some tricks. It > > Can't we simply register a hypercall ID range with Microsoft? > > > may also affect WHQLing Windows drivers since driver will talk to HW > > bypassing Windows interfaces. > > Then the WHQL'ed driver doesn't support the PV MMIO hcall? ==
KVM "Hyper-V emulation" -- this can be related "Linux on Hyper-V" ?
Best regards, Victor Miasnikov Blog: http://vvm.blog.tut.by/
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