On 17.11.2013, at 20:09, Liu Ping Fan <qemul...@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
>
> Signed-off-by: Liu Ping Fan <pingf...@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;
> - }
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 = 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
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
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