Re: [PATCH 7/7] KVM: MIPS: clean up redundant kvm_run parameters in assembly

Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx> · Mon, 20 Apr 2020 18:42:15 +0800

On 2020/4/20 18:32, maobibo wrote:


On 04/19/2020 03:51 PM, Tianjia Zhang wrote:
In the current kvm version, 'kvm_run' has been included in the 'kvm_vcpu'
structure. Earlier than historical reasons, many kvm-related function
parameters retain the 'kvm_run' and 'kvm_vcpu' parameters at the same time.
This patch does a unified cleanup of these remaining redundant parameters.

Signed-off-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
---
  arch/mips/include/asm/kvm_host.h |  4 ++--
  arch/mips/kvm/entry.c            | 15 +++++----------
  arch/mips/kvm/mips.c             |  3 ++-
  arch/mips/kvm/trap_emul.c        |  2 +-
  arch/mips/kvm/vz.c               |  2 +-
  5 files changed, 11 insertions(+), 15 deletions(-)

diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index 971439297cea..db915c55166d 100644
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -310,7 +310,7 @@ struct kvm_mmu_memory_cache {
  #define KVM_MIPS_GUEST_TLB_SIZE	64
  struct kvm_vcpu_arch {
  	void *guest_ebase;
-	int (*vcpu_run)(struct kvm_run *run, struct kvm_vcpu *vcpu);
+	int (*vcpu_run)(struct kvm_vcpu *vcpu);
  
  	/* Host registers preserved across guest mode execution */
  	unsigned long host_stack;
@@ -821,7 +821,7 @@ int kvm_mips_emulation_init(struct kvm_mips_callbacks **install_callbacks);
  /* Debug: dump vcpu state */
  int kvm_arch_vcpu_dump_regs(struct kvm_vcpu *vcpu);
  
-extern int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu);
+extern int kvm_mips_handle_exit(struct kvm_vcpu *vcpu);
  
  /* Building of entry/exception code */
  int kvm_mips_entry_setup(void);
diff --git a/arch/mips/kvm/entry.c b/arch/mips/kvm/entry.c
index 16e1c93b484f..e3f29af3b6cd 100644
--- a/arch/mips/kvm/entry.c
+++ b/arch/mips/kvm/entry.c
@@ -204,7 +204,7 @@ static inline void build_set_exc_base(u32 **p, unsigned int reg)
   * Assemble the start of the vcpu_run function to run a guest VCPU. The function
   * conforms to the following prototype:
   *
- * int vcpu_run(struct kvm_run *run, struct kvm_vcpu *vcpu);
+ * int vcpu_run(struct kvm_vcpu *vcpu);
   *
   * The exit from the guest and return to the caller is handled by the code
   * generated by kvm_mips_build_ret_to_host().
@@ -217,8 +217,7 @@ void *kvm_mips_build_vcpu_run(void *addr)
  	unsigned int i;
  
  	/*
-	 * A0: run
-	 * A1: vcpu
+	 * A0: vcpu
  	 */
  
  	/* k0/k1 not being used in host kernel context */
@@ -237,10 +236,10 @@ void *kvm_mips_build_vcpu_run(void *addr)
  	kvm_mips_build_save_scratch(&p, V1, K1);
  
  	/* VCPU scratch register has pointer to vcpu */
-	UASM_i_MTC0(&p, A1, scratch_vcpu[0], scratch_vcpu[1]);
+	UASM_i_MTC0(&p, A0, scratch_vcpu[0], scratch_vcpu[1]);
  
  	/* Offset into vcpu->arch */
-	UASM_i_ADDIU(&p, K1, A1, offsetof(struct kvm_vcpu, arch));
+	UASM_i_ADDIU(&p, K1, A0, offsetof(struct kvm_vcpu, arch));
  
  	/*
  	 * Save the host stack to VCPU, used for exception processing
@@ -628,10 +627,7 @@ void *kvm_mips_build_exit(void *addr)
  	/* Now that context has been saved, we can use other registers */
  
  	/* Restore vcpu */
-	UASM_i_MFC0(&p, S1, scratch_vcpu[0], scratch_vcpu[1]);
-
-	/* Restore run (vcpu->run) */
-	UASM_i_LW(&p, S0, offsetof(struct kvm_vcpu, run), S1);
+	UASM_i_MFC0(&p, S0, scratch_vcpu[0], scratch_vcpu[1]);
  
  	/*
  	 * Save Host level EPC, BadVaddr and Cause to VCPU, useful to process
@@ -793,7 +789,6 @@ void *kvm_mips_build_exit(void *addr)
  	 * with this in the kernel
  	 */
  	uasm_i_move(&p, A0, S0);
-	uasm_i_move(&p, A1, S1);
  	UASM_i_LA(&p, T9, (unsigned long)kvm_mips_handle_exit);
  	uasm_i_jalr(&p, RA, T9);
  	 UASM_i_ADDIU(&p, SP, SP, -CALLFRAME_SIZ);

I suggest keeping asm code untouched, the change for c code is much easier to understand, however I do not see obvious advantage to remove one redundant function parameter :)


regards
bibo,mao


This is acceptable, asm code is an independent patch, is to provide 
convenience for this operation.


diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 9710477a9827..32850470c037 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -1186,8 +1186,9 @@ static void kvm_mips_set_c0_status(void)
  /*
   * Return value is in the form (errcode<<2 | RESUME_FLAG_HOST | RESUME_FLAG_NV)
   */
-int kvm_mips_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu)
+int kvm_mips_handle_exit(struct kvm_vcpu *vcpu)
  {
+	struct kvm_run *run = vcpu->run;
  	u32 cause = vcpu->arch.host_cp0_cause;
  	u32 exccode = (cause >> CAUSEB_EXCCODE) & 0x1f;
  	u32 __user *opc = (u32 __user *) vcpu->arch.pc;
diff --git a/arch/mips/kvm/trap_emul.c b/arch/mips/kvm/trap_emul.c
index d822f3aee3dc..04c864cc356a 100644
--- a/arch/mips/kvm/trap_emul.c
+++ b/arch/mips/kvm/trap_emul.c
@@ -1238,7 +1238,7 @@ static int kvm_trap_emul_vcpu_run(struct kvm_vcpu *vcpu)
  	 */
  	kvm_mips_suspend_mm(cpu);
  
-	r = vcpu->arch.vcpu_run(vcpu->run, vcpu);
+	r = vcpu->arch.vcpu_run(vcpu);
  
  	/* We may have migrated while handling guest exits */
  	cpu = smp_processor_id();
diff --git a/arch/mips/kvm/vz.c b/arch/mips/kvm/vz.c
index 94f1d23828e3..c5878fa0636d 100644
--- a/arch/mips/kvm/vz.c
+++ b/arch/mips/kvm/vz.c
@@ -3152,7 +3152,7 @@ static int kvm_vz_vcpu_run(struct kvm_vcpu *vcpu)
  	kvm_vz_vcpu_load_tlb(vcpu, cpu);
  	kvm_vz_vcpu_load_wired(vcpu);
  
-	r = vcpu->arch.vcpu_run(vcpu->run, vcpu);
+	r = vcpu->arch.vcpu_run(vcpu);
  
  	kvm_vz_vcpu_save_wired(vcpu);
  

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