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From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Liran Alon <liran.alon@oracle.com>,
	kvm@vger.kernel.org, Jim Mattson <jmattson@google.com>,
	linux-kernel@vger.kernel.org, Roman Kagan <rkagan@virtuozzo.com>
Subject: Re: [PATCH RFC 3/3] x86/kvm/hyper-v: don't allow to turn on unsupported VMX controls for nested guests
Date: Sun, 19 Jan 2020 09:57:28 +0100
Message-ID: <cdfcbb9d-42fd-1189-1dac-4ece14708890@redhat.com> (raw)
In-Reply-To: <20200116162101.GD20561@linux.intel.com>

On 16/01/20 17:21, Sean Christopherson wrote:
> On Thu, Jan 16, 2020 at 09:55:57AM +0100, Vitaly Kuznetsov wrote:
>> Liran Alon <liran.alon@oracle.com> writes:
>>
>>>> On 15 Jan 2020, at 19:10, Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
>>>>
>>>> Sane L1 hypervisors are not supposed to turn any of the unsupported VMX
>>>> controls on for its guests and nested_vmx_check_controls() checks for
>>>> that. This is, however, not the case for the controls which are supported
>>>> on the host but are missing in enlightened VMCS and when eVMCS is in use.
>>>>
>>>> It would certainly be possible to add these missing checks to
>>>> nested_check_vm_execution_controls()/_vm_exit_controls()/.. but it seems
>>>> preferable to keep eVMCS-specific stuff in eVMCS and reduce the impact on
>>>> non-eVMCS guests by doing less unrelated checks. Create a separate
>>>> nested_evmcs_check_controls() for this purpose.
>>>>
>>>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>>>> ---
>>>> arch/x86/kvm/vmx/evmcs.c  | 56 ++++++++++++++++++++++++++++++++++++++-
>>>> arch/x86/kvm/vmx/evmcs.h  |  1 +
>>>> arch/x86/kvm/vmx/nested.c |  3 +++
>>>> 3 files changed, 59 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c
>>>> index b5d6582ba589..88f462866396 100644
>>>> --- a/arch/x86/kvm/vmx/evmcs.c
>>>> +++ b/arch/x86/kvm/vmx/evmcs.c
>>>> @@ -4,9 +4,11 @@
>>>> #include <linux/smp.h>
>>>>
>>>> #include "../hyperv.h"
>>>> -#include "evmcs.h"
>>>> #include "vmcs.h"
>>>> +#include "vmcs12.h"
>>>> +#include "evmcs.h"
>>>> #include "vmx.h"
>>>> +#include "trace.h"
>>>>
>>>> DEFINE_STATIC_KEY_FALSE(enable_evmcs);
>>>>
>>>> @@ -378,6 +380,58 @@ void nested_evmcs_filter_control_msr(u32 msr_index, u64 *pdata)
>>>> 	*pdata = ctl_low | ((u64)ctl_high << 32);
>>>> }
>>>>
>>>> +int nested_evmcs_check_controls(struct vmcs12 *vmcs12)
>>>> +{
>>>> +	int ret = 0;
>>>> +	u32 unsupp_ctl;
>>>> +
>>>> +	unsupp_ctl = vmcs12->pin_based_vm_exec_control &
>>>> +		EVMCS1_UNSUPPORTED_PINCTRL;
>>>> +	if (unsupp_ctl) {
>>>> +		trace_kvm_nested_vmenter_failed(
>>>> +			"eVMCS: unsupported pin-based VM-execution controls",
>>>> +			unsupp_ctl);
>>>
>>> Why not move "CC” macro from nested.c to nested.h and use it here as-well instead of replicating it’s logic?
>>>
>>
>> Because error messages I add are both human readable and conform to SDM!
>> :-)
>>
>> On a more serious not yes, we should probably do that. We may even want
>> to use it in non-nesting (and non VMX) code in KVM.
> 
> No, the CC() macro is short for Consistency Check, i.e. specific to nVMX.
> Even if KVM ends up adding nested_evmcs_check_controls(), which I'm hoping
> can be avoided, I'd still be hesitant to expose CC() in nested.h.
> 

For now let's keep Vitaly's patch as is.  It's definitely a good one as
it would catch Hyper-V's issue immediately even without patch 2 (which
is the only really contentious change).

Paolo


      reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-15 17:10 [PATCH RFC 0/3] x86/kvm/hyper-v: fix enlightened VMCS & QEMU4.2 Vitaly Kuznetsov
2020-01-15 17:10 ` [PATCH RFC 1/3] x86/kvm/hyper-v: remove stale evmcs_already_enabled check from nested_enable_evmcs() Vitaly Kuznetsov
2020-01-15 22:50   ` Liran Alon
2020-01-15 17:10 ` [PATCH RFC 2/3] x86/kvm/hyper-v: move VMX controls sanitization out of nested_enable_evmcs() Vitaly Kuznetsov
2020-01-15 22:49   ` Liran Alon
2020-01-16  8:37     ` Vitaly Kuznetsov
2020-02-03 15:11       ` Vitaly Kuznetsov
2020-01-15 23:27   ` Sean Christopherson
2020-01-15 23:30     ` Liran Alon
2020-01-16  8:51       ` Vitaly Kuznetsov
2020-01-16 16:19         ` Sean Christopherson
2020-01-16 16:57           ` Vitaly Kuznetsov
2020-01-17  6:31             ` Sean Christopherson
2020-01-18 21:42           ` Paolo Bonzini
2020-01-19  8:54   ` Paolo Bonzini
2020-01-22  5:47     ` Sean Christopherson
2020-01-22  9:37       ` Vitaly Kuznetsov
2020-01-22 14:33       ` Paolo Bonzini
2020-01-22 15:08         ` Vitaly Kuznetsov
2020-01-22 15:51           ` Sean Christopherson
2020-01-22 16:29             ` Vitaly Kuznetsov
2020-01-22 16:40               ` Paolo Bonzini
2020-01-23  9:15                 ` Vitaly Kuznetsov
2020-01-23 19:09                   ` Vitaly Kuznetsov
2020-01-24 17:25                     ` Sean Christopherson
2020-01-27 15:38                       ` Vitaly Kuznetsov
2020-01-27 17:53                         ` Paolo Bonzini
2020-01-27 21:52                           ` Vitaly Kuznetsov
2020-01-27 18:17                         ` Sean Christopherson
2020-01-15 17:10 ` [PATCH RFC 3/3] x86/kvm/hyper-v: don't allow to turn on unsupported VMX controls for nested guests Vitaly Kuznetsov
2020-01-15 22:59   ` Liran Alon
2020-01-16  8:55     ` Vitaly Kuznetsov
2020-01-16 16:21       ` Sean Christopherson
2020-01-19  8:57         ` Paolo Bonzini [this message]

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