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([2601:647:4700:9b2:6553:6836:584f:1008]) by smtp.gmail.com with ESMTPSA id v1sm7424946pjs.36.2020.04.25.09.54.08 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Sat, 25 Apr 2020 09:54:09 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.80.23.2.2\)) Subject: Re: [RFC PATCH 1/3] kvm: x86: Rename KVM_DEBUGREG_RELOAD to KVM_DEBUGREG_NEED_RELOAD From: Nadav Amit In-Reply-To: <85cb5946-2109-28a0-578d-bed31d1b8298@redhat.com> Date: Sat, 25 Apr 2020 09:54:07 -0700 Cc: Xiaoyao Li , Sean Christopherson , kvm , Nadav Amit , Vitaly Kuznetsov , linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: <08C6D1FB-A4F7-49FA-AC46-5323C104840A@gmail.com> References: <20200416101509.73526-1-xiaoyao.li@intel.com> <20200416101509.73526-2-xiaoyao.li@intel.com> <85cb5946-2109-28a0-578d-bed31d1b8298@redhat.com> To: Paolo Bonzini X-Mailer: Apple Mail (2.3608.80.23.2.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Apr 25, 2020, at 1:07 AM, Paolo Bonzini = wrote: >=20 > On 16/04/20 12:15, Xiaoyao Li wrote: >> To make it more clear that the flag means DRn (except DR7) need to be >> reloaded before vm entry. >>=20 >> Signed-off-by: Xiaoyao Li >=20 > I wonder if KVM_DEBUGREG_RELOAD is needed at all. It should be easy = to > write selftests for it, using the testcase in commit message > 172b2386ed16 and the information in commit ae561edeb421. I must be missing something, since I did not follow this thread and = other KVM changes very closely. Yet, for the record, I added KVM_DEBUGREG_RELOAD due to real experienced issues that I had while running Intel=E2=80=99s fuzzing tests on KVM: = IIRC, the DRs were not reloaded after an INIT event that clears them. Personally, I would prefer that a test for that, if added, would be = added to KVM-unit-tests, based on Liran=E2=80=99s INIT test. This would allow = to confirm bare-metal behaves as the VM.