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Mon, 31 Mar 2025 01:23:18 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 52V8Mp0A3171319 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025032001; t=1743409400; bh=K1q53eo/E11QGaBNCmuuiEewoEjYIhJFKtCNyzdMWfk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fYJJM8Xj8oLRQMrpq1oZ9Rnts/L5sB1pkc/gbLLiuGLqwOG9qwxAGu/4BG68QY0E9 wfBdSwh4eQvvh2/Y3Z6WaX7t7pE5x/AyF9EYYVoeYUsrgjy5aQsLhKl3r8wbyqsS8o qh1pRd13tdt4PmpmLxqluvo/m8RcpuW2x76HH/JRrb1yV8WiUIE4hCpEtDNED/Yh+6 sNVHvloh/CyqgKztI+Tc3MQqU27RJiZ6HQl+pwJmYWKADo2kfVmQTIr7agdhUDKEDb anOJ6HwZplUeZ1KVIk1BWCIusZV2JYQ1KiyYhKxPqQ6qOrnhQXCF8X6edaiE7NigVe yW2IFXjim5dUQ== From: "Xin Li (Intel)" To: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, linux-hyperv@vger.kernel.org, virtualization@lists.linux.dev, linux-edac@vger.kernel.org, kvm@vger.kernel.org, xen-devel@lists.xenproject.org, linux-ide@vger.kernel.org, linux-pm@vger.kernel.org, bpf@vger.kernel.org, llvm@lists.linux.dev Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, jgross@suse.com, andrew.cooper3@citrix.com, peterz@infradead.org, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, wei.liu@kernel.org, ajay.kaher@broadcom.com, alexey.amakhalov@broadcom.com, bcm-kernel-feedback-list@broadcom.com, tony.luck@intel.com, pbonzini@redhat.com, vkuznets@redhat.com, seanjc@google.com, luto@kernel.org, boris.ostrovsky@oracle.com, kys@microsoft.com, haiyangz@microsoft.com, decui@microsoft.com Subject: [RFC PATCH v1 10/15] KVM: VMX: Use WRMSRNS or its immediate form when available Date: Mon, 31 Mar 2025 01:22:46 -0700 Message-ID: <20250331082251.3171276-11-xin@zytor.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250331082251.3171276-1-xin@zytor.com> References: <20250331082251.3171276-1-xin@zytor.com> Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Signed-off-by: Xin Li (Intel) --- arch/x86/include/asm/msr-index.h | 6 ++++++ arch/x86/kvm/vmx/vmenter.S | 28 ++++++++++++++++++++++++---- 2 files changed, 30 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h index e6134ef2263d..04244c3ba374 100644 --- a/arch/x86/include/asm/msr-index.h +++ b/arch/x86/include/asm/msr-index.h @@ -1226,4 +1226,10 @@ * a #GP */ +/* Instruction opcode for WRMSRNS supported in binutils >= 2.40 */ +#define ASM_WRMSRNS _ASM_BYTES(0x0f,0x01,0xc6) + +/* Instruction opcode for the immediate form RDMSR/WRMSRNS */ +#define ASM_WRMSRNS_RAX _ASM_BYTES(0xc4,0xe7,0x7a,0xf6,0xc0) + #endif /* _ASM_X86_MSR_INDEX_H */ diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S index f6986dee6f8c..9fae43723c44 100644 --- a/arch/x86/kvm/vmx/vmenter.S +++ b/arch/x86/kvm/vmx/vmenter.S @@ -64,6 +64,29 @@ RET .endm +/* + * Write EAX to MSR_IA32_SPEC_CTRL. + * + * Choose the best WRMSR instruction based on availability. + * + * Replace with 'wrmsrns' and 'wrmsrns %rax, $MSR_IA32_SPEC_CTRL' once binutils support them. + */ +.macro WRITE_EAX_TO_MSR_IA32_SPEC_CTRL + ALTERNATIVE_2 __stringify(mov $MSR_IA32_SPEC_CTRL, %ecx; \ + xor %edx, %edx; \ + mov %edi, %eax; \ + ds wrmsr), \ + __stringify(mov $MSR_IA32_SPEC_CTRL, %ecx; \ + xor %edx, %edx; \ + mov %edi, %eax; \ + ASM_WRMSRNS), \ + X86_FEATURE_WRMSRNS, \ + __stringify(xor %_ASM_AX, %_ASM_AX; \ + mov %edi, %eax; \ + ASM_WRMSRNS_RAX; .long MSR_IA32_SPEC_CTRL), \ + X86_FEATURE_MSR_IMM +.endm + .section .noinstr.text, "ax" /** @@ -123,10 +146,7 @@ SYM_FUNC_START(__vmx_vcpu_run) movl PER_CPU_VAR(x86_spec_ctrl_current), %esi cmp %edi, %esi je .Lspec_ctrl_done - mov $MSR_IA32_SPEC_CTRL, %ecx - xor %edx, %edx - mov %edi, %eax - wrmsr + WRITE_EAX_TO_MSR_IA32_SPEC_CTRL .Lspec_ctrl_done: