Re: [PATCH v2 3/4] kvm/ppc: Call trace_hardirqs_on before entry

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On 05/10/2013 11:34 AM, Bhushan Bharat-R65777 wrote:


-----Original Message-----
From: kvm-owner@xxxxxxxxxxxxxxx [mailto:kvm-owner@xxxxxxxxxxxxxxx] On Behalf Of
Scott Wood
Sent: Friday, May 10, 2013 8:40 AM
To: Alexander Graf; Benjamin Herrenschmidt
Cc: kvm-ppc@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; linuxppc-dev@xxxxxxxxxxxxxxxx;
Wood Scott-B07421
Subject: [PATCH v2 3/4] kvm/ppc: Call trace_hardirqs_on before entry

Currently this is only being done on 64-bit.  Rather than just move it
out of the 64-bit ifdef, move it to kvm_lazy_ee_enable() so that it is
consistent with lazy ee state, and so that we don't track more host
code as interrupts-enabled than necessary.

Rename kvm_lazy_ee_enable() to kvm_fix_ee_before_entry() to reflect
that this function now has a role on 32-bit as well.

Signed-off-by: Scott Wood <scottwood@xxxxxxxxxxxxx>
---
  arch/powerpc/include/asm/kvm_ppc.h |   11 ++++++++---
  arch/powerpc/kvm/book3s_pr.c       |    4 ++--
  arch/powerpc/kvm/booke.c           |    4 ++--
  arch/powerpc/kvm/powerpc.c         |    2 --
  4 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_ppc.h
b/arch/powerpc/include/asm/kvm_ppc.h
index a5287fe..6885846 100644
--- a/arch/powerpc/include/asm/kvm_ppc.h
+++ b/arch/powerpc/include/asm/kvm_ppc.h
@@ -394,10 +394,15 @@ static inline void kvmppc_mmu_flush_icache(pfn_t pfn)
  	}
  }

-/* Please call after prepare_to_enter. This function puts the lazy ee state
-   back to normal mode, without actually enabling interrupts. */
-static inline void kvmppc_lazy_ee_enable(void)
+/*
+ * Please call after prepare_to_enter. This function puts the lazy ee and irq
+ * disabled tracking state back to normal mode, without actually enabling
+ * interrupts.
+ */
+static inline void kvmppc_fix_ee_before_entry(void)
  {
+	trace_hardirqs_on();
+
  #ifdef CONFIG_PPC64
  	/* Only need to enable IRQs by hard enabling them after this */
  	local_paca->irq_happened = 0;
diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c
index bdc40b8..0b97ce4 100644
--- a/arch/powerpc/kvm/book3s_pr.c
+++ b/arch/powerpc/kvm/book3s_pr.c
@@ -890,7 +890,7 @@ program_interrupt:
  			local_irq_enable();
  			r = s;
  		} else {
-			kvmppc_lazy_ee_enable();
+			kvmppc_fix_ee_before_entry();
  		}
  	}

@@ -1161,7 +1161,7 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct
kvm_vcpu *vcpu)
  	if (vcpu->arch.shared->msr & MSR_FP)
  		kvmppc_handle_ext(vcpu, BOOK3S_INTERRUPT_FP_UNAVAIL, MSR_FP);

-	kvmppc_lazy_ee_enable();
+	kvmppc_fix_ee_before_entry();

  	ret = __kvmppc_vcpu_run(kvm_run, vcpu);

diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 705fc5c..eb89b83 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -673,7 +673,7 @@ int kvmppc_vcpu_run(struct kvm_run *kvm_run, struct kvm_vcpu
*vcpu)
  		ret = s;
  		goto out;
  	}
-	kvmppc_lazy_ee_enable();
+	kvmppc_fix_ee_before_entry();

local_irq_disable() is called before kvmppc_prepare_to_enter().

In patch 4, we call hard_irq_disable() once enter kvmppc_prepare_to_enter().

Tiejun

Now we put the irq_happend and soft_enabled back to previous state without checking for any interrupt happened in between. If any interrupt happens in between, will not that be lost?

-Bharat


  	kvm_guest_enter();

@@ -1154,7 +1154,7 @@ int kvmppc_handle_exit(struct kvm_run *run, struct
kvm_vcpu *vcpu,
  			local_irq_enable();
  			r = (s << 2) | RESUME_HOST | (r & RESUME_FLAG_NV);
  		} else {
-			kvmppc_lazy_ee_enable();
+			kvmppc_fix_ee_before_entry();
  		}
  	}

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 6316ee3..4e05f8c 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -117,8 +117,6 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
  			kvm_guest_exit();
  			continue;
  		}
-
-		trace_hardirqs_on();
  #endif

  		kvm_guest_enter();
--
1.7.10.4


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