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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id g186sm19977226wma.1.2020.11.13.03.26.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 13 Nov 2020 03:26:21 -0800 (PST) Subject: Re: [PATCH] KVM: x86: clflushopt should be treated as a no-op by emulation To: David Edmondson , linux-kernel@vger.kernel.org Cc: Vitaly Kuznetsov , Nadav Amit , x86@kernel.org, Wanpeng Li , kvm@vger.kernel.org, Thomas Gleixner , Sean Christopherson , "H. Peter Anvin" , Joerg Roedel , Jim Mattson , Borislav Petkov , Ingo Molnar References: <20201103120400.240882-1-david.edmondson@oracle.com> From: Paolo Bonzini Message-ID: <72b96832-634a-56f0-95aa-f9a282d8fbf8@redhat.com> Date: Fri, 13 Nov 2020 12:26:20 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0 MIME-Version: 1.0 In-Reply-To: <20201103120400.240882-1-david.edmondson@oracle.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/11/20 13:04, David Edmondson wrote: > The instruction emulator ignores clflush instructions, yet fails to > support clflushopt. Treat both similarly. > > Fixes: 13e457e0eebf ("KVM: x86: Emulator does not decode clflush well") > Signed-off-by: David Edmondson > --- > arch/x86/kvm/emulate.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c > index 0d917eb70319..56cae1ff9e3f 100644 > --- a/arch/x86/kvm/emulate.c > +++ b/arch/x86/kvm/emulate.c > @@ -4046,6 +4046,12 @@ static int em_clflush(struct x86_emulate_ctxt *ctxt) > return X86EMUL_CONTINUE; > } > > +static int em_clflushopt(struct x86_emulate_ctxt *ctxt) > +{ > + /* emulating clflushopt regardless of cpuid */ > + return X86EMUL_CONTINUE; > +} > + > static int em_movsxd(struct x86_emulate_ctxt *ctxt) > { > ctxt->dst.val = (s32) ctxt->src.val; > @@ -4585,7 +4591,7 @@ static const struct opcode group11[] = { > }; > > static const struct gprefix pfx_0f_ae_7 = { > - I(SrcMem | ByteOp, em_clflush), N, N, N, > + I(SrcMem | ByteOp, em_clflush), I(SrcMem | ByteOp, em_clflushopt), N, N, > }; > > static const struct group_dual group15 = { { > Queued, thanks. Paolo