[v3,18/33] KVM: VMX: Pass "launched" directly to the vCPU-run asm blob

Commit Message

Sean Christopherson Jan. 25, 2019, 3:41 p.m. UTC

...and remove struct vcpu_vmx's temporary __launched variable.

Eliminating __launched is a bonus, the real motivation is to get to the
point where the only reference to struct vcpu_vmx in the asm code is
to vcpu.arch.regs, which will simplify moving the blob to a proper asm
file.  Note that also means this approach is deliberately different than
what is used in nested_vmx_check_vmentry_hw().

Use BL as it is a non-volatile register in both 32-bit and 64-bit ABIs,
i.e. it can't be modified by vmx_update_host_rsp(), to avoid having to
temporarily save/restore the launched flag.

Signed-off-by: Sean Christopherson <[e-mail]>
---
 arch/x86/kvm/vmx/vmx.c | 13 ++++++-------
 arch/x86/kvm/vmx/vmx.h |  2 +-
 2 files changed, 7 insertions(+), 8 deletions(-)

Comments

Jim Mattson Jan. 28, 2019, 10:37 p.m. UTC | #1

On Fri, Jan 25, 2019 at 7:42 AM Sean Christopherson
<[e-mail]> wrote:
>
> ...and remove struct vcpu_vmx's temporary __launched variable.
>
> Eliminating __launched is a bonus, the real motivation is to get to the
> point where the only reference to struct vcpu_vmx in the asm code is
> to vcpu.arch.regs, which will simplify moving the blob to a proper asm
> file.  Note that also means this approach is deliberately different than
> what is used in nested_vmx_check_vmentry_hw().
>
> Use BL as it is a non-volatile register in both 32-bit and 64-bit ABIs,
> i.e. it can't be modified by vmx_update_host_rsp(), to avoid having to
> temporarily save/restore the launched flag.
>
> Signed-off-by: Sean Christopherson <[e-mail]>
Reviewed-by: Jim Mattson <[e-mail]>

Patch

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 70d1e951b33d..51ac6a2a1fc5 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6372,8 +6372,6 @@  void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
 
 static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
 {
-	vmx->__launched = vmx->loaded_vmcs->launched;
-
 	if (static_branch_unlikely(&vmx_l1d_should_flush))
 		vmx_l1d_flush(vcpu);
 
@@ -6394,7 +6392,8 @@  static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
 		"mov (%%" _ASM_SP "), %%" _ASM_CX " \n\t"
 
 		/* Check if vmlaunch or vmresume is needed */
-		"cmpb $0, %c[launched](%%" _ASM_CX ") \n\t"
+		"cmpb $0, %%bl \n\t"
+
 		/* Load guest registers.  Don't clobber flags. */
 		"mov %c[rax](%%" _ASM_CX "), %%" _ASM_AX " \n\t"
 		"mov %c[rbx](%%" _ASM_CX "), %%" _ASM_BX " \n\t"
@@ -6470,7 +6469,7 @@  static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
 		"xor %%edi, %%edi \n\t"
 		"xor %%ebp, %%ebp \n\t"
 		"pop  %%" _ASM_BP " \n\t"
-	      : ASM_CALL_CONSTRAINT,
+	      : ASM_CALL_CONSTRAINT, "=b"((int){0}),
 #ifdef CONFIG_X86_64
 		"=D"((int){0})
 	      : "D"(vmx),
@@ -6478,7 +6477,7 @@  static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
 		"=a"((int){0})
 	      : "a"(vmx),
 #endif
-		[launched]"i"(offsetof(struct vcpu_vmx, __launched)),
+		"b"(vmx->loaded_vmcs->launched),
 		[fail]"i"(offsetof(struct vcpu_vmx, fail)),
 		[rax]"i"(offsetof(struct vcpu_vmx, vcpu.arch.regs[VCPU_REGS_RAX])),
 		[rbx]"i"(offsetof(struct vcpu_vmx, vcpu.arch.regs[VCPU_REGS_RBX])),
@@ -6500,10 +6499,10 @@  static void __vmx_vcpu_run(struct kvm_vcpu *vcpu, struct vcpu_vmx *vmx)
 		[wordsize]"i"(sizeof(ulong))
 	      : "cc", "memory"
 #ifdef CONFIG_X86_64
-		, "rax", "rbx", "rcx", "rdx", "rsi"
+		, "rax", "rcx", "rdx", "rsi"
 		, "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15"
 #else
-		, "ebx", "ecx", "edx", "edi", "esi"
+		, "ecx", "edx", "edi", "esi"
 #endif
 	      );
 
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index 8e203b725928..6ee6a492efaf 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -208,7 +208,7 @@  struct vcpu_vmx {
 	struct loaded_vmcs    vmcs01;
 	struct loaded_vmcs   *loaded_vmcs;
 	struct loaded_vmcs   *loaded_cpu_state;
-	bool                  __launched; /* temporary, used in vmx_vcpu_run */
+
 	struct msr_autoload {
 		struct vmx_msrs guest;
 		struct vmx_msrs host;