* [PATCH v3] powerpc: kvm: optimize "sc 1" as fast return
@ 2013-11-18 1:09 Liu Ping Fan
2013-11-18 20:45 ` Alexander Graf
0 siblings, 1 reply; 4+ messages in thread
From: Liu Ping Fan @ 2013-11-18 1:09 UTC (permalink / raw)
To: linuxppc-dev, kvm-ppc; +Cc: Paul Mackerras, Alexander Graf
In some scene, e.g openstack CI, PR guest can trigger "sc 1" frequently,
this patch optimizes the path by directly delivering BOOK3S_INTERRUPT_SYSCALL
to HV guest, so powernv can return to HV guest without heavy exit, i.e,
no need to swap TLB, HTAB,.. etc
Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
---
arch/powerpc/kvm/book3s_hv.c | 6 ------
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 12 +++++++++++-
2 files changed, 11 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 62a2b5a..73dc852 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -628,12 +628,6 @@ static int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
/* hcall - punt to userspace */
int i;
- if (vcpu->arch.shregs.msr & MSR_PR) {
- /* sc 1 from userspace - reflect to guest syscall */
- kvmppc_book3s_queue_irqprio(vcpu, BOOK3S_INTERRUPT_SYSCALL);
- r = RESUME_GUEST;
- break;
- }
run->papr_hcall.nr = kvmppc_get_gpr(vcpu, 3);
for (i = 0; i < 9; ++i)
run->papr_hcall.args[i] = kvmppc_get_gpr(vcpu, 4 + i);
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index c71103b..0d1e2c2 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -1388,7 +1388,8 @@ kvmppc_hisi:
hcall_try_real_mode:
ld r3,VCPU_GPR(R3)(r9)
andi. r0,r11,MSR_PR
- bne guest_exit_cont
+ /* sc 1 from userspace - reflect to guest syscall */
+ bne sc_1_fast_return
clrrdi r3,r3,2
cmpldi r3,hcall_real_table_end - hcall_real_table
bge guest_exit_cont
@@ -1409,6 +1410,15 @@ hcall_try_real_mode:
ld r11,VCPU_MSR(r4)
b fast_guest_return
+sc_1_fast_return:
+ mtspr SPRN_SRR0,r10
+ mtspr SPRN_SRR1,r11
+ li r10, BOOK3S_INTERRUPT_SYSCALL
+ li r11, (MSR_ME << 1) | 1 /* synthesize MSR_SF | MSR_ME */
+ rotldi r11, r11, 63
+ mr r4,r9
+ b fast_guest_return
+
/* We've attempted a real mode hcall, but it's punted it back
* to userspace. We need to restore some clobbered volatiles
* before resuming the pass-it-to-qemu path */
--
1.8.1.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v3] powerpc: kvm: optimize "sc 1" as fast return
2013-11-18 1:09 [PATCH v3] powerpc: kvm: optimize "sc 1" as fast return Liu Ping Fan
@ 2013-11-18 20:45 ` Alexander Graf
0 siblings, 0 replies; 4+ messages in thread
From: Alexander Graf @ 2013-11-18 20:45 UTC (permalink / raw)
To: Liu Ping Fan; +Cc: Paul Mackerras, linuxppc-dev, kvm-ppc
On 17.11.2013, at 20:09, Liu Ping Fan <qemulist@gmail.com> wrote:
> In some scene, e.g openstack CI, PR guest can trigger "sc 1" =
frequently,
> this patch optimizes the path by directly delivering =
BOOK3S_INTERRUPT_SYSCALL
> to HV guest, so powernv can return to HV guest without heavy exit, =
i.e,
> no need to swap TLB, HTAB,.. etc
>=20
> Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
> ---
> arch/powerpc/kvm/book3s_hv.c | 6 ------
> arch/powerpc/kvm/book3s_hv_rmhandlers.S | 12 +++++++++++-
> 2 files changed, 11 insertions(+), 7 deletions(-)
>=20
> diff --git a/arch/powerpc/kvm/book3s_hv.c =
b/arch/powerpc/kvm/book3s_hv.c
> index 62a2b5a..73dc852 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -628,12 +628,6 @@ static int kvmppc_handle_exit(struct kvm_run =
*run, struct kvm_vcpu *vcpu,
> /* hcall - punt to userspace */
> int i;
>=20
> - if (vcpu->arch.shregs.msr & MSR_PR) {
> - /* sc 1 from userspace - reflect to guest =
syscall */
> - kvmppc_book3s_queue_irqprio(vcpu, =
BOOK3S_INTERRUPT_SYSCALL);
> - r =3D RESUME_GUEST;
> - break;
> - }
Please document the fact that we never get here for
1) hypercall with MSR_PR
2) hypercall that was handled by rm code
so that when anyone reads the C file he doesn't have to dig through =
piles of asm code to understand what's happening.
> run->papr_hcall.nr =3D kvmppc_get_gpr(vcpu, 3);
> for (i =3D 0; i < 9; ++i)
> run->papr_hcall.args[i] =3D kvmppc_get_gpr(vcpu, =
4 + i);
> diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S =
b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> index c71103b..0d1e2c2 100644
> --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> @@ -1388,7 +1388,8 @@ kvmppc_hisi:
> hcall_try_real_mode:
> ld r3,VCPU_GPR(R3)(r9)
> andi. r0,r11,MSR_PR
> - bne guest_exit_cont
> + /* sc 1 from userspace - reflect to guest syscall */
> + bne sc_1_fast_return
> clrrdi r3,r3,2
> cmpldi r3,hcall_real_table_end - hcall_real_table
> bge guest_exit_cont
> @@ -1409,6 +1410,15 @@ hcall_try_real_mode:
> ld r11,VCPU_MSR(r4)
> b fast_guest_return
>=20
> +sc_1_fast_return:
> + mtspr SPRN_SRR0,r10
> + mtspr SPRN_SRR1,r11
> + li r10, BOOK3S_INTERRUPT_SYSCALL
> + li r11, (MSR_ME << 1) | 1 /* synthesize MSR_SF | MSR_ME */
> + rotldi r11, r11, 63
> + mr r4,r9
> + b fast_guest_return
While at it, please also document the input registers to =
fast_guest_return. As you've seen it's very easy to get them right when =
they're not properly documented in the header of the function.
Apart from these minor bits, the patch looks very sound and hopefully =
speeds up PR-in-HV by quite a bit.
Alex
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH v3] powerpc: kvm: optimize "sc 1" as fast return
2013-11-19 6:12 [PATCH RESEND v4] powerpc: kvm: fix rare but potential deadlock scene Liu Ping Fan
@ 2013-11-19 6:12 ` Liu Ping Fan
2013-11-19 10:40 ` Alexander Graf
0 siblings, 1 reply; 4+ messages in thread
From: Liu Ping Fan @ 2013-11-19 6:12 UTC (permalink / raw)
To: linuxppc-dev, kvm-ppc
Cc: kvm, Gleb Natapov, Alexander Graf, Paul Mackerras, Paolo Bonzini
In some scene, e.g openstack CI, PR guest can trigger "sc 1" frequently,
this patch optimizes the path by directly delivering BOOK3S_INTERRUPT_SYSCALL
to HV guest, so powernv can return to HV guest without heavy exit, i.e,
no need to swap TLB, HTAB,.. etc
Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
---
v3: add some document
---
arch/powerpc/kvm/book3s_hv.c | 10 ++++------
arch/powerpc/kvm/book3s_hv_rmhandlers.S | 19 ++++++++++++++++++-
2 files changed, 22 insertions(+), 7 deletions(-)
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 62a2b5a..1addb1a 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -628,12 +628,10 @@ static int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
/* hcall - punt to userspace */
int i;
- if (vcpu->arch.shregs.msr & MSR_PR) {
- /* sc 1 from userspace - reflect to guest syscall */
- kvmppc_book3s_queue_irqprio(vcpu, BOOK3S_INTERRUPT_SYSCALL);
- r = RESUME_GUEST;
- break;
- }
+ /* hypercall with MSR_PR has already been handled in rmode,
+ * and never reaches here.
+ */
+
run->papr_hcall.nr = kvmppc_get_gpr(vcpu, 3);
for (i = 0; i < 9; ++i)
run->papr_hcall.args[i] = kvmppc_get_gpr(vcpu, 4 + i);
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index c71103b..eea7ca7 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -534,6 +534,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206)
5: mtspr SPRN_SRR0, r6
mtspr SPRN_SRR1, r7
+/*
+ * Required state:
+ * R4 = vcpu
+ * R10: value for HSRR0
+ * R11: value for HSRR1
+ * R13 = PACA
+ */
fast_guest_return:
li r0,0
stb r0,VCPU_CEDED(r4) /* cancel cede */
@@ -1388,7 +1395,8 @@ kvmppc_hisi:
hcall_try_real_mode:
ld r3,VCPU_GPR(R3)(r9)
andi. r0,r11,MSR_PR
- bne guest_exit_cont
+ /* sc 1 from userspace - reflect to guest syscall */
+ bne sc_1_fast_return
clrrdi r3,r3,2
cmpldi r3,hcall_real_table_end - hcall_real_table
bge guest_exit_cont
@@ -1409,6 +1417,15 @@ hcall_try_real_mode:
ld r11,VCPU_MSR(r4)
b fast_guest_return
+sc_1_fast_return:
+ mtspr SPRN_SRR0,r10
+ mtspr SPRN_SRR1,r11
+ li r10, BOOK3S_INTERRUPT_SYSCALL
+ li r11, (MSR_ME << 1) | 1 /* synthesize MSR_SF | MSR_ME */
+ rotldi r11, r11, 63
+ mr r4,r9
+ b fast_guest_return
+
/* We've attempted a real mode hcall, but it's punted it back
* to userspace. We need to restore some clobbered volatiles
* before resuming the pass-it-to-qemu path */
--
1.8.1.4
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH v3] powerpc: kvm: optimize "sc 1" as fast return
2013-11-19 6:12 ` [PATCH v3] powerpc: kvm: optimize "sc 1" as fast return Liu Ping Fan
@ 2013-11-19 10:40 ` Alexander Graf
0 siblings, 0 replies; 4+ messages in thread
From: Alexander Graf @ 2013-11-19 10:40 UTC (permalink / raw)
To: Liu Ping Fan
Cc: Gleb Natapov, kvm@vger.kernel.org mailing list, kvm-ppc,
Paul Mackerras, Paolo Bonzini, linuxppc-dev
On 19.11.2013, at 07:12, Liu Ping Fan <kernelfans@gmail.com> wrote:
> In some scene, e.g openstack CI, PR guest can trigger "sc 1" =
frequently,
> this patch optimizes the path by directly delivering =
BOOK3S_INTERRUPT_SYSCALL
> to HV guest, so powernv can return to HV guest without heavy exit, =
i.e,
> no need to swap TLB, HTAB,.. etc
>=20
> Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
> ---
> v3: add some document
This is v4 I think
> ---
> arch/powerpc/kvm/book3s_hv.c | 10 ++++------
> arch/powerpc/kvm/book3s_hv_rmhandlers.S | 19 ++++++++++++++++++-
> 2 files changed, 22 insertions(+), 7 deletions(-)
>=20
> diff --git a/arch/powerpc/kvm/book3s_hv.c =
b/arch/powerpc/kvm/book3s_hv.c
> index 62a2b5a..1addb1a 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -628,12 +628,10 @@ static int kvmppc_handle_exit(struct kvm_run =
*run, struct kvm_vcpu *vcpu,
> /* hcall - punt to userspace */
> int i;
>=20
> - if (vcpu->arch.shregs.msr & MSR_PR) {
> - /* sc 1 from userspace - reflect to guest =
syscall */
> - kvmppc_book3s_queue_irqprio(vcpu, =
BOOK3S_INTERRUPT_SYSCALL);
> - r =3D RESUME_GUEST;
> - break;
> - }
> + /* hypercall with MSR_PR has already been handled in =
rmode,
> + * and never reaches here.
> + */
It would've been nice to also mention the real mode hypercall handling, =
but I can just post a follow-up patch for that one.
Thanks, applied to kvm-ppc-queue.
Alex
^ permalink raw reply [flat|nested] 4+ messages in thread
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2013-11-19 6:12 [PATCH RESEND v4] powerpc: kvm: fix rare but potential deadlock scene Liu Ping Fan
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