[05/29] KVM: VMX: Manually load RDX in vCPU-run asm blob

Message ID	20190118212037.24412-6-sean.j.christopherson@intel.com (mailing list archive)
State	New, archived
Headers	show Return-Path: <kvm-owner@kernel.org> From: Sean Christopherson <sean.j.christopherson@intel.com> To: Paolo Bonzini <pbonzini@redhat.com>, =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com> Cc: kvm@vger.kernel.org, Andi Kleen <ak@linux.intel.com>, Josh Poimboeuf <jpoimboe@redhat.com> Subject: [PATCH 05/29] KVM: VMX: Manually load RDX in vCPU-run asm blob Date: Fri, 18 Jan 2019 13:20:13 -0800 Message-Id: <20190118212037.24412-6-sean.j.christopherson@intel.com> In-Reply-To: <20190118212037.24412-1-sean.j.christopherson@intel.com> References: <20190118212037.24412-1-sean.j.christopherson@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: kvm-owner@vger.kernel.org Precedence: bulk
Series	KVM: VMX: Move vCPU-run to proper asm sub-routine \| expand [00/29] KVM: VMX: Move vCPU-run to proper asm sub-routine [01/29] KVM: VMX: Compare only a single byte for VMCS' "launched" in vCPU-run [02/29] KVM: nVMX: Check a single byte for VMCS "launched" in nested early checks [03/29] KVM: VMX: Modify only RSP when creating a placeholder for guest's RCX [04/29] KVM: VMX: Save RSI to an unused output in the vCPU-run asm blob [05/29] KVM: VMX: Manually load RDX in vCPU-run asm blob [06/29] KVM: VMX: Let the compiler save/load RDX during vCPU-run [07/29] KVM: nVMX: Remove a rogue "rax" clobber from nested_vmx_check_vmentry_hw() [08/29] KVM: nVMX: Drop STACK_FRAME_NON_STANDARD from nested_vmx_check_vmentry_hw() [09/29] KVM: nVMX: Explicitly reference the scratch reg in nested early checks [10/29] KVM: nVMX: Capture VM-Fail to a local var in nested_vmx_check_vmentry_hw() [11/29] KVM: nVMX: Capture VM-Fail via CC_{SET,OUT} in nested early checks [12/29] KVM: nVMX: Reference vmx->loaded_vmcs->launched directly [13/29] KVM: nVMX: Let the compiler select the reg for holding HOST_RSP [14/29] KVM: nVMX: Cache host_rsp on a per-VMCS basis [15/29] KVM: VMX: Load/save guest CR2 via C code in __vmx_vcpu_run() [16/29] KVM: VMX: Update VMCS.HOST_RSP via helper C function [17/29] KVM: VMX: Pass "launched" directly to the vCPU-run asm blob [18/29] KVM: VMX: Invert the ordering of saving guest/host scratch reg at VM-Enter [19/29] KVM: VMX: Don't save guest registers after VM-Fail [20/29] KVM: VMX: Use vcpu->arch.regs directly when saving/loading guest state [21/29] KVM: x86: Explicitly #define the VCPU_REGS_* indices [22/29] KVM: VMX: Use #defines in place of immediates in VM-Enter inline asm [23/29] KVM: VMX: Create a stack frame in vCPU-run [24/29] KVM: VMX: Move vCPU-run code to a proper assembly routine [25/29] KVM: VMX: Fold __vmx_vcpu_run() back into vmx_vcpu_run() [26/29] KVM: VMX: Rename ____vmx_vcpu_run() to __vmx_vcpu_run() [27/29] KVM: VMX: Use RAX as the scratch register during vCPU-run [28/29] KVM: VMX: Make the vCPU-run asm routine callable from C [29/29] KVM: VMX: Reorder clearing of registers in the vCPU-run assembly flow

Message ID

20190118212037.24412-6-sean.j.christopherson@intel.com (mailing list archive)

State

New, archived

Headers

From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
 =?utf-8?b?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>
Cc: kvm@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>
Subject: [PATCH 05/29] KVM: VMX: Manually load RDX in vCPU-run asm blob
Date: Fri, 18 Jan 2019 13:20:13 -0800
Message-Id: <20190118212037.24412-6-sean.j.christopherson@intel.com>
In-Reply-To: <20190118212037.24412-1-sean.j.christopherson@intel.com>
References: <20190118212037.24412-1-sean.j.christopherson@intel.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: kvm-owner@vger.kernel.org
Precedence: bulk

Series

KVM: VMX: Move vCPU-run to proper asm sub-routine | expand

Commit Message

Sean Christopherson Jan. 18, 2019, 9:20 p.m. UTC

Load RDX with the VMCS.HOST_RSP field encoding on-demand instead of
delegating to the compiler via an input constraint.  In addition to
saving one whole MOV instruction, this allows RDX to be properly
clobbered (in a future patch) instead of being saved/loaded to/from
the stack.

Despite nested_vmx_check_vmentry_hw() having similar code, leave it
alone, for now.  In that case, RDX is unconditionally used and isn't
clobbered, i.e. sending in HOST_RSP as an input is simpler.

Note that because HOST_RSP is an enum and not a define, it must be
redefined as an immediate instead of using __stringify(HOST_RSP).  The
naming "conflict" between host_rsp and HOST_RSP is slightly confusing,
but the former will be removed in a future patch, at which point
HOST_RSP is absolutely what is desired.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
 arch/x86/kvm/vmx/vmx.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index e8e2e289828d..57d83f401ed5 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6389,6 +6389,7 @@  static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
 		"mov %%" _ASM_SP ", (%%" _ASM_SI ") \n\t"
 		"jmp 1f \n\t"
 		"2: \n\t"
+		"mov $%c[HOST_RSP], %%" _ASM_DX " \n\t"
 		__ex("vmwrite %%" _ASM_SP ", %%" _ASM_DX) "\n\t"
 		"1: \n\t"
 		"add $%c[wordsize], %%" _ASM_SP "\n\t" /* un-adjust RSP */
@@ -6473,10 +6474,11 @@  static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
 		"xor %%edi, %%edi \n\t"
 		"pop  %%" _ASM_BP "; pop  %%" _ASM_DX " \n\t"
 	      : ASM_CALL_CONSTRAINT, "=S"((int){0})
-	      : "c"(vmx), "d"((unsigned long)HOST_RSP), "S"(evmcs_rsp),
+	      : "c"(vmx), "S"(evmcs_rsp),
 		[launched]"i"(offsetof(struct vcpu_vmx, __launched)),
 		[fail]"i"(offsetof(struct vcpu_vmx, fail)),
 		[host_rsp]"i"(offsetof(struct vcpu_vmx, host_rsp)),
+		[HOST_RSP]"i"(HOST_RSP),
 		[rax]"i"(offsetof(struct vcpu_vmx, vcpu.arch.regs[VCPU_REGS_RAX])),
 		[rbx]"i"(offsetof(struct vcpu_vmx, vcpu.arch.regs[VCPU_REGS_RBX])),
 		[rcx]"i"(offsetof(struct vcpu_vmx, vcpu.arch.regs[VCPU_REGS_RCX])),

[05/29] KVM: VMX: Manually load RDX in vCPU-run asm blob

Commit Message

Patch