Re: [PATCH] KVM/nVMX: Use __vmx_vcpu_run in nested_vmx_check_vmentry_hw

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On 17/12/20 19:44, Uros Bizjak wrote:
Replace inline assembly in nested_vmx_check_vmentry_hw
with a call to __vmx_vcpu_run.  The function is not
performance critical, so (double) GPR save/restore
in __vmx_vcpu_run can be tolerated, as far as performance
effects are concerned.

v2: Mark vmx_vmenter SYM_FUNC_START_LOCAL.

Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Reviewed-and-tested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
---
  arch/x86/kvm/vmx/nested.c  | 32 +++-----------------------------
  arch/x86/kvm/vmx/vmenter.S |  2 +-
  arch/x86/kvm/vmx/vmx.c     |  2 --
  arch/x86/kvm/vmx/vmx.h     |  1 +
  4 files changed, 5 insertions(+), 32 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 89af692deb7e..6ab62bf277c4 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -12,6 +12,7 @@
  #include "nested.h"
  #include "pmu.h"
  #include "trace.h"
+#include "vmx.h"
  #include "x86.h"
static bool __read_mostly enable_shadow_vmcs = 1;
@@ -3056,35 +3057,8 @@ static int nested_vmx_check_vmentry_hw(struct kvm_vcpu *vcpu)
  		vmx->loaded_vmcs->host_state.cr4 = cr4;
  	}
- asm(
-		"sub $%c[wordsize], %%" _ASM_SP "\n\t" /* temporarily adjust RSP for CALL */
-		"cmp %%" _ASM_SP ", %c[host_state_rsp](%[loaded_vmcs]) \n\t"
-		"je 1f \n\t"
-		__ex("vmwrite %%" _ASM_SP ", %[HOST_RSP]") "\n\t"
-		"mov %%" _ASM_SP ", %c[host_state_rsp](%[loaded_vmcs]) \n\t"
-		"1: \n\t"
-		"add $%c[wordsize], %%" _ASM_SP "\n\t" /* un-adjust RSP */
-
-		/* Check if vmlaunch or vmresume is needed */
-		"cmpb $0, %c[launched](%[loaded_vmcs])\n\t"
-
-		/*
-		 * VMLAUNCH and VMRESUME clear RFLAGS.{CF,ZF} on VM-Exit, set
-		 * RFLAGS.CF on VM-Fail Invalid and set RFLAGS.ZF on VM-Fail
-		 * Valid.  vmx_vmenter() directly "returns" RFLAGS, and so the
-		 * results of VM-Enter is captured via CC_{SET,OUT} to vm_fail.
-		 */
-		"call vmx_vmenter\n\t"
-
-		CC_SET(be)
-	      : ASM_CALL_CONSTRAINT, CC_OUT(be) (vm_fail)
-	      :	[HOST_RSP]"r"((unsigned long)HOST_RSP),
-		[loaded_vmcs]"r"(vmx->loaded_vmcs),
-		[launched]"i"(offsetof(struct loaded_vmcs, launched)),
-		[host_state_rsp]"i"(offsetof(struct loaded_vmcs, host_state.rsp)),
-		[wordsize]"i"(sizeof(ulong))
-	      : "memory"
-	);
+	vm_fail = __vmx_vcpu_run(vmx, (unsigned long *)&vcpu->arch.regs,
+				 vmx->loaded_vmcs->launched);
if (vmx->msr_autoload.host.nr)
  		vmcs_write32(VM_EXIT_MSR_LOAD_COUNT, vmx->msr_autoload.host.nr);
diff --git a/arch/x86/kvm/vmx/vmenter.S b/arch/x86/kvm/vmx/vmenter.S
index 90ad7a6246e3..14abe1e37359 100644
--- a/arch/x86/kvm/vmx/vmenter.S
+++ b/arch/x86/kvm/vmx/vmenter.S
@@ -44,7 +44,7 @@
   * they VM-Fail, whereas a successful VM-Enter + VM-Exit will jump
   * to vmx_vmexit.
   */
-SYM_FUNC_START(vmx_vmenter)
+SYM_FUNC_START_LOCAL(vmx_vmenter)
  	/* EFLAGS.ZF is set if VMCS.LAUNCHED == 0 */
  	je 2f
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 47b8357b9751..72b496c54bc9 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6593,8 +6593,6 @@ static fastpath_t vmx_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
  	}
  }
-bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned long *regs, bool launched);
-
  static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
  					struct vcpu_vmx *vmx)
  {
diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
index f6f66e5c6510..32db3b033e9b 100644
--- a/arch/x86/kvm/vmx/vmx.h
+++ b/arch/x86/kvm/vmx/vmx.h
@@ -339,6 +339,7 @@ void vmx_set_virtual_apic_mode(struct kvm_vcpu *vcpu);
  struct vmx_uret_msr *vmx_find_uret_msr(struct vcpu_vmx *vmx, u32 msr);
  void pt_update_intercept_for_msr(struct kvm_vcpu *vcpu);
  void vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp);
+bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned long *regs, bool launched);
  int vmx_find_loadstore_msr_slot(struct vmx_msrs *m, u32 msr);
  void vmx_ept_load_pdptrs(struct kvm_vcpu *vcpu);

Queued, thanks.

Paolo




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