linux-kernel - [PATCH v6 0/4] KVM: nSVM: ondemand nested state allocation

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Message-Id: <20200922211025.175547-1-mlevitsk@redhat.com>
Date:   Wed, 23 Sep 2020 00:10:21 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     kvm@...r.kernel.org
Cc:     "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, Jim Mattson <jmattson@...gle.com>,
        x86@...nel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: [PATCH v6 0/4] KVM: nSVM: ondemand nested state allocation

This is the next version of this patch series.

In V5 I adopted Sean Christopherson's suggestion to make .set_efer return
a negative error (-ENOMEM in this case) which in most cases in kvm
propagates to the userspace.

I noticed though that wrmsr emulation code doesn't do this and instead
it injects #GP to the guest on _any_ error.

So I fixed the wrmsr code to behave in a similar way to the rest
of the kvm code.
(#GP only on a positive error value, and forward the negative error to
the userspace)

I had to adjust one wrmsr handler (xen_hvm_config) to stop it from returning
negative values	so that new WRMSR emulation behavior doesn't break it.
This patch was only compile tested.

The memory allocation failure was tested by always returning -ENOMEM
from svm_allocate_nested.

The nested allocation itself was tested by countless attempts to run
nested guests, do nested migration on both my AMD and Intel machines.
I wasn't able to break it.

Changes from V5: addressed Sean Christopherson's review feedback.

Best regards,
	Maxim Levitsky

Maxim Levitsky (4):
  KVM: x86: xen_hvm_config: cleanup return values
  KVM: x86: report negative values from wrmsr emulation to userspace
  KVM: x86: allow kvm_x86_ops.set_efer to return an error value
  KVM: nSVM: implement on demand allocation of the nested state

 arch/x86/include/asm/kvm_host.h |  2 +-
 arch/x86/kvm/emulate.c          |  7 ++--
 arch/x86/kvm/svm/nested.c       | 42 ++++++++++++++++++++++++
 arch/x86/kvm/svm/svm.c          | 58 +++++++++++++++++++--------------
 arch/x86/kvm/svm/svm.h          |  8 ++++-
 arch/x86/kvm/vmx/vmx.c          |  6 ++--
 arch/x86/kvm/x86.c              | 37 ++++++++++++---------
 7 files changed, 113 insertions(+), 47 deletions(-)

-- 
2.26.2