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Mon, 02 Dec 2024 17:28:55 -0800 (PST) Received: from [192.168.86.29] ([90.240.255.120]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-aa5997d560asm563452966b.61.2024.12.02.17.28.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Dec 2024 17:28:55 -0800 (PST) Message-ID: Date: Tue, 3 Dec 2024 01:28:54 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 1/2] x86, lib, xenpv: Add WBNOINVD helper functions To: Kevin Loughlin , linux-kernel@vger.kernel.org Cc: seanjc@google.com, pbonzini@redhat.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, kvm@vger.kernel.org, thomas.lendacky@amd.com, pgonda@google.com, sidtelang@google.com, mizhang@google.com, virtualization@lists.linux.dev, xen-devel@lists.xenproject.org, bcm-kernel-feedback-list@broadcom.com References: <20241203005921.1119116-1-kevinloughlin@google.com> <20241203005921.1119116-2-kevinloughlin@google.com> Content-Language: en-GB From: Andrew Cooper Autocrypt: addr=andrew.cooper3@citrix.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 03/12/2024 12:59 am, Kevin Loughlin wrote: > diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h > index d4eb9e1d61b8..c040af2d8eff 100644 > --- a/arch/x86/include/asm/paravirt.h > +++ b/arch/x86/include/asm/paravirt.h > @@ -187,6 +187,13 @@ static __always_inline void wbinvd(void) > PVOP_ALT_VCALL0(cpu.wbinvd, "wbinvd", ALT_NOT_XEN); > } > > +extern noinstr void pv_native_wbnoinvd(void); > + > +static __always_inline void wbnoinvd(void) > +{ > + PVOP_ALT_VCALL0(cpu.wbnoinvd, "wbnoinvd", ALT_NOT_XEN); > +} Given this, ... > diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c > index fec381533555..a66b708d8a1e 100644 > --- a/arch/x86/kernel/paravirt.c > +++ b/arch/x86/kernel/paravirt.c > @@ -149,6 +154,7 @@ struct paravirt_patch_template pv_ops = { > .cpu.write_cr0 = native_write_cr0, > .cpu.write_cr4 = native_write_cr4, > .cpu.wbinvd = pv_native_wbinvd, > + .cpu.wbnoinvd = pv_native_wbnoinvd, > .cpu.read_msr = native_read_msr, > .cpu.write_msr = native_write_msr, > .cpu.read_msr_safe = native_read_msr_safe, this, and ... > diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c > index d6818c6cafda..a5c76a6f8976 100644 > --- a/arch/x86/xen/enlighten_pv.c > +++ b/arch/x86/xen/enlighten_pv.c > @@ -1162,6 +1162,7 @@ static const typeof(pv_ops) xen_cpu_ops __initconst = { > .write_cr4 = xen_write_cr4, > > .wbinvd = pv_native_wbinvd, > + .wbnoinvd = pv_native_wbnoinvd, > > .read_msr = xen_read_msr, > .write_msr = xen_write_msr, this, what is the point having a paravirt hook which is wired to native_wbnoinvd() in all cases? That just seems like overhead for overhead sake. ~Andrew