Re: [PATCH v2] KVM: Optimize kvm_arch_vcpu_ioctl_run function

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On 2020-04-16 08:03, Vitaly Kuznetsov wrote:
Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx> writes:

In earlier versions of kvm, 'kvm_run' is an independent structure
and is not included in the vcpu structure. At present, 'kvm_run'
is already included in the vcpu structure, so the parameter
'kvm_run' is redundant.

This patch simplify the function definition, removes the extra
'kvm_run' parameter, and extract it from the 'kvm_vcpu' structure
if necessary.

Signed-off-by: Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx>
---

v2 change:
  remove 'kvm_run' parameter and extract it from 'kvm_vcpu'

 arch/mips/kvm/mips.c       |  3 ++-
 arch/powerpc/kvm/powerpc.c |  3 ++-
 arch/s390/kvm/kvm-s390.c   |  3 ++-
 arch/x86/kvm/x86.c         | 11 ++++++-----
 include/linux/kvm_host.h   |  2 +-
 virt/kvm/arm/arm.c         |  6 +++---
 virt/kvm/kvm_main.c        |  2 +-
 7 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 8f05dd0a0f4e..ec24adf4857e 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -439,8 +439,9 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
 	return -ENOIOCTLCMD;
 }

-int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
+int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 {
+	struct kvm_run *run = vcpu->run;
 	int r = -EINTR;

 	vcpu_load(vcpu);
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index e15166b0a16d..7e24691e138a 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -1764,8 +1764,9 @@ int kvm_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu, struct kvm_one_reg *reg)
 	return r;
 }

-int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
+int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 {
+	struct kvm_run *run = vcpu->run;
 	int r;

 	vcpu_load(vcpu);
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 19a81024fe16..443af3ead739 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4333,8 +4333,9 @@ static void store_regs(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 		store_regs_fmt2(vcpu, kvm_run);
 }

-int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
+int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 {
+	struct kvm_run *kvm_run = vcpu->run;
 	int rc;

 	if (kvm_run->immediate_exit)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3bf2ecafd027..a0338e86c90f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8707,8 +8707,9 @@ static void kvm_put_guest_fpu(struct kvm_vcpu *vcpu)
 	trace_kvm_fpu(0);
 }

-int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
+int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 {
+	struct kvm_run *kvm_run = vcpu->run;
 	int r;

 	vcpu_load(vcpu);
@@ -8726,18 +8727,18 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
 		r = -EAGAIN;
 		if (signal_pending(current)) {
 			r = -EINTR;
-			vcpu->run->exit_reason = KVM_EXIT_INTR;
+			kvm_run->exit_reason = KVM_EXIT_INTR;
 			++vcpu->stat.signal_exits;
 		}
 		goto out;
 	}

-	if (vcpu->run->kvm_valid_regs & ~KVM_SYNC_X86_VALID_FIELDS) {
+	if (kvm_run->kvm_valid_regs & ~KVM_SYNC_X86_VALID_FIELDS) {
 		r = -EINVAL;
 		goto out;
 	}

-	if (vcpu->run->kvm_dirty_regs) {
+	if (kvm_run->kvm_dirty_regs) {
 		r = sync_regs(vcpu);
 		if (r != 0)
 			goto out;
@@ -8767,7 +8768,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)

 out:
 	kvm_put_guest_fpu(vcpu);
-	if (vcpu->run->kvm_valid_regs)
+	if (kvm_run->kvm_valid_regs)
 		store_regs(vcpu);
 	post_kvm_run_save(vcpu);
 	kvm_sigset_deactivate(vcpu);
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 6d58beb65454..1e17ef719595 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -866,7 +866,7 @@ int kvm_arch_vcpu_ioctl_set_mpstate(struct kvm_vcpu *vcpu,
 				    struct kvm_mp_state *mp_state);
 int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
 					struct kvm_guest_debug *dbg);
-int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run);
+int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu);

 int kvm_arch_init(void *opaque);
 void kvm_arch_exit(void);
diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 48d0ec44ad77..f5390ac2165b 100644
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -639,7 +639,6 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
 /**
* kvm_arch_vcpu_ioctl_run - the main VCPU run function to execute guest code
  * @vcpu:	The VCPU pointer
- * @run: The kvm_run structure pointer used for userspace state exchange
  *
* This function is called through the VCPU_RUN ioctl called from user space. It * will execute VM code in a loop until the time slice for the process is used @@ -647,8 +646,9 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu) * return with return value 0 and with the kvm_run structure filled in with the
  * required data for the requested emulation.
  */
-int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
+int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 {
+	struct kvm_run *run = vcpu->run;
 	int ret;

 	if (unlikely(!kvm_vcpu_initialized(vcpu)))
@@ -659,7 +659,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 		return ret;

 	if (run->exit_reason == KVM_EXIT_MMIO) {
-		ret = kvm_handle_mmio_return(vcpu, vcpu->run);
+		ret = kvm_handle_mmio_return(vcpu, run);

I don't know much about ARM but this also seems redundant,
kvm_handle_mmio_return() is also able to extruct 'struct kvm_run' from'
'struct kvm_vcpu'. This likely deserves it's own patch though.

Something like this (untested):

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 32c8a675e5a4..82978995bdd6 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -490,7 +490,7 @@ void handle_exit_early(struct kvm_vcpu *vcpu, struct kvm_run *run, void kvm_mmio_write_buf(void *buf, unsigned int len, unsigned long data);
 unsigned long kvm_mmio_read_buf(const void *buf, unsigned int len);

-int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run);
+int kvm_handle_mmio_return(struct kvm_vcpu *vcpu);
 int io_mem_abort(struct kvm_vcpu *vcpu, struct kvm_run *run,
 		 phys_addr_t fault_ipa);

diff --git a/virt/kvm/arm/mmio.c b/virt/kvm/arm/mmio.c
index 4e0366759726..3b2c822b4859 100644
--- a/virt/kvm/arm/mmio.c
+++ b/virt/kvm/arm/mmio.c
@@ -77,9 +77,8 @@ unsigned long kvm_mmio_read_buf(const void *buf, unsigned int len)
  *			     or in-kernel IO emulation
  *
  * @vcpu: The VCPU pointer
- * @run:  The VCPU run struct containing the mmio data
  */
-int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
+int kvm_handle_mmio_return(struct kvm_vcpu *vcpu)
 {
 	unsigned long data;
 	unsigned int len;
@@ -93,7 +92,7 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run)

 	if (!kvm_vcpu_dabt_iswrite(vcpu)) {
 		len = kvm_vcpu_dabt_get_as(vcpu);
-		data = kvm_mmio_read_buf(run->mmio.data, len);
+		data = kvm_mmio_read_buf(vcpu->run->mmio.data, len);

 		if (kvm_vcpu_dabt_issext(vcpu) &&
 		    len < sizeof(unsigned long)) {
@@ -104,7 +103,8 @@ int kvm_handle_mmio_return(struct kvm_vcpu *vcpu, struct kvm_run *run)
 		if (!kvm_vcpu_dabt_issf(vcpu))
 			data = data & 0xffffffff;

-		trace_kvm_mmio(KVM_TRACE_MMIO_READ, len, run->mmio.phys_addr,
+		trace_kvm_mmio(KVM_TRACE_MMIO_READ, len,
+			       vcpu->run->mmio.phys_addr,
 			       &data);
 		data = vcpu_data_host_to_guest(vcpu, data, len);
 		vcpu_set_reg(vcpu, kvm_vcpu_dabt_get_rd(vcpu), data);

Overall, there is a large set of cleanups to be done when both the vcpu and the run structures are passed as parameters at the same time. Just grepping the tree for
kvm_run is pretty instructive.

        M.
--
Jazz is not dead. It just smells funny...



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