[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <46052d1e-9ee1-8cee-3f7c-cf27b1cd0373@redhat.com>
Date: Wed, 25 Jul 2018 14:14:49 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: kvm@...r.kernel.org,
Radim Krčmář <rkrcmar@...hat.com>,
Roman Kagan <rkagan@...tuozzo.com>,
"K. Y. Srinivasan" <kys@...rosoft.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Stephen Hemminger <sthemmin@...rosoft.com>,
"Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>,
Mohammed Gamal <mmorsy@...hat.com>,
Cathy Avery <cavery@...hat.com>, linux-kernel@...r.kernel.org,
Jim Mattson <jmattson@...gle.com>,
Liran Alon <liran.alon@...cle.com>
Subject: Re: [PATCH v2 6/6] KVM: nVMX: optimize prepare_vmcs02{,_full} for
Enlightened VMCS case
On 25/07/2018 10:37, Vitaly Kuznetsov wrote:
>> Why is this needed? If it weren't for it, you could pass hv_evmcs
>> directly to evmcs_needs_write, which would simplify the code a bit in
>> the caller.
> This is an equivalent of prepare_vmcs02()/prepare_vmcs02_full() split
> for eVMCS case: when we switch from L2 guest A to L2 guest B we need to
> write the whole VMCS so evmcs_needs_write() needs to return true.
Right, I missed the dirty_vmcs12 assignment in patch 5.
But is L0 allowed to write to hv_clean_fields? One possibility is to
add a dirty_evmcs field to struct nested_vmx, and "OR" ~hv_clean_fields
into it at the beginning of prepare_vmcs02.
Something like
if (vmx->nested.hv_evmcs) {
vmx->nested.dirty_evmcs |=
~vmx->nested.hv_evmcs->hv_clean_fields;
prepare_vmcs02_full(vcpu, vmcs12,
vmx->nested.dirty_evmcs);
} else if (vmx->nested.dirty_vmcs12) {
prepare_vmcs02_full(vcpu, vmcs12, ~0);
}
...
vmx->nested.dirty_evmcs = 0;
vmx->nested.dirty_vmcs12 = false;
?
Paolo
> We can, however, make an optimisation: forcefuly reset hv_clean_fields
> mask on enlightened vmptrld making 'dirty_vmcs12' check redundant.
Powered by blists - more mailing lists