From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Liran Alon <liran.alon@oracle.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: [PATCH] x86/kvm/nVMCS: fix VMCLEAR when Enlightened VMCS is in use
Date: Tue, 25 Jun 2019 10:51:56 +0200 [thread overview]
Message-ID: <87lfxqdp3n.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <CEFF2A14-611A-417C-BC0A-8814862F26C6@oracle.com>
Liran Alon <liran.alon@oracle.com> writes:
>> On 24 Jun 2019, at 16:30, Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
>>
>>
>> +bool nested_enlightened_vmentry(struct kvm_vcpu *vcpu, u64 *evmptr)
>
> I prefer to rename evmptr to evmcs_ptr. I think it’s more readable and sufficiently short.
> In addition, I think you should return either -1ull or assist_page.current_nested_vmcs.
> i.e. Don’t return evmcs_ptr by pointer but instead as a return-value
> and get rid of the bool.
Actually no, sorry, I'm having second thoughts here: in handle_vmclear()
we don't care about the value of evmcs_ptr, we only want to check that
enlightened vmentry bit is enabled in assist page. If we switch to
checking evmcs_ptr against '-1', for example, we will make '-1' a magic
value which is not in the TLFS. Windows may decide to use it for
something else - and we will get a hard-to-debug bug again.
If you still dislike nested_enlightened_vmentry() having the side effect
of fetching evmcs_ptr I can get rid of it by splitting the function into
two, however, it will be less efficient for
nested_vmx_handle_enlightened_vmptrld(). Or we can just leave things as
they are there and use the newly introduced function in handle_vmclear()
only.
--
Vitaly
next prev parent reply other threads:[~2019-06-25 8:52 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-24 13:30 [PATCH] x86/kvm/nVMCS: fix VMCLEAR when Enlightened VMCS is in use Vitaly Kuznetsov
2019-06-24 13:41 ` Liran Alon
2019-06-24 14:16 ` Vitaly Kuznetsov
2019-06-24 14:45 ` Liran Alon
2019-06-26 9:39 ` Vitaly Kuznetsov
2019-06-26 12:10 ` Paolo Bonzini
2019-06-25 8:51 ` Vitaly Kuznetsov [this message]
2019-06-25 11:01 ` Liran Alon
2019-06-25 11:15 ` Vitaly Kuznetsov
2019-06-25 11:18 ` Liran Alon
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