Re: [PATCH v2] KVM: Optimize kvm_arch_vcpu_ioctl_run function

Marc Zyngier
2020-04-16T09:14:33Z

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