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From: Nicholas Piggin <npiggin@gmail.com>
To: kvm-ppc@vger.kernel.org
Cc: Fabiano Rosas <farosas@linux.ibm.com>,
	linuxppc-dev@lists.ozlabs.org,
	Nicholas Piggin <npiggin@gmail.com>,
	Daniel Axtens <dja@axtens.net>
Subject: [PATCH v1 10/12] powerpc/64s: remove KVM SKIP test from instruction breakpoint handler
Date: Mon, 12 Apr 2021 11:48:43 +1000	[thread overview]
Message-ID: <20210412014845.1517916-11-npiggin@gmail.com> (raw)
In-Reply-To: <20210412014845.1517916-1-npiggin@gmail.com>

The code being executed in KVM_GUEST_MODE_SKIP is hypervisor code with
MSR[IR]=0, so the faults of concern are the d-side ones caused by access
to guest context by the hypervisor.

Instruction breakpoint interrupts are not a concern here. It's unlikely
any good would come of causing breaks in this code, but skipping the
instruction that caused it won't help matters (e.g., skip the mtmsr that
sets MSR[DR]=0 or clears KVM_GUEST_MODE_SKIP).

 [Paul notes: "the 0x1300 interrupt was dropped from the architecture a
  long time ago and is not generated by P7, P8, P9 or P10." So add a
  comment about this in the handler code while we're here. ]

Acked-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kernel/exceptions-64s.S | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index a0515cb829c2..358cd4b0c08e 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -2549,11 +2549,16 @@ EXC_REAL_NONE(0x1200, 0x100)
 EXC_VIRT_NONE(0x5200, 0x100)
 #endif
 
-
+/**
+ * Interrupt 0x1300 - Instruction Address Breakpoint Interrupt.
+ * This has been removed from the ISA before 2.01, which is the earliest
+ * 64-bit BookS ISA supported, however the G5 / 970 implements this
+ * interrupt with a non-architected feature available through the support
+ * processor interface.
+ */
 INT_DEFINE_BEGIN(instruction_breakpoint)
 	IVEC=0x1300
 #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
-	IKVM_SKIP=1
 	IKVM_REAL=1
 #endif
 INT_DEFINE_END(instruction_breakpoint)
-- 
2.23.0


WARNING: multiple messages have this Message-ID (diff)
From: Nicholas Piggin <npiggin@gmail.com>
To: kvm-ppc@vger.kernel.org
Cc: Fabiano Rosas <farosas@linux.ibm.com>,
	linuxppc-dev@lists.ozlabs.org,
	Nicholas Piggin <npiggin@gmail.com>,
	Daniel Axtens <dja@axtens.net>
Subject: [PATCH v1 10/12] powerpc/64s: remove KVM SKIP test from instruction breakpoint handler
Date: Mon, 12 Apr 2021 01:48:43 +0000	[thread overview]
Message-ID: <20210412014845.1517916-11-npiggin@gmail.com> (raw)
In-Reply-To: <20210412014845.1517916-1-npiggin@gmail.com>

The code being executed in KVM_GUEST_MODE_SKIP is hypervisor code with
MSR[IR]=0, so the faults of concern are the d-side ones caused by access
to guest context by the hypervisor.

Instruction breakpoint interrupts are not a concern here. It's unlikely
any good would come of causing breaks in this code, but skipping the
instruction that caused it won't help matters (e.g., skip the mtmsr that
sets MSR[DR]=0 or clears KVM_GUEST_MODE_SKIP).

 [Paul notes: "the 0x1300 interrupt was dropped from the architecture a
  long time ago and is not generated by P7, P8, P9 or P10." So add a
  comment about this in the handler code while we're here. ]

Acked-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: Daniel Axtens <dja@axtens.net>
Reviewed-by: Fabiano Rosas <farosas@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kernel/exceptions-64s.S | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index a0515cb829c2..358cd4b0c08e 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -2549,11 +2549,16 @@ EXC_REAL_NONE(0x1200, 0x100)
 EXC_VIRT_NONE(0x5200, 0x100)
 #endif
 
-
+/**
+ * Interrupt 0x1300 - Instruction Address Breakpoint Interrupt.
+ * This has been removed from the ISA before 2.01, which is the earliest
+ * 64-bit BookS ISA supported, however the G5 / 970 implements this
+ * interrupt with a non-architected feature available through the support
+ * processor interface.
+ */
 INT_DEFINE_BEGIN(instruction_breakpoint)
 	IVEC=0x1300
 #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
-	IKVM_SKIP=1
 	IKVM_REAL=1
 #endif
 INT_DEFINE_END(instruction_breakpoint)
-- 
2.23.0

  parent reply	other threads:[~2021-04-12  1:53 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-12  1:48 [PATCH v1 00/12] minor KVM fixes and cleanups Nicholas Piggin
2021-04-12  1:48 ` Nicholas Piggin
2021-04-12  1:48 ` [PATCH v1 01/12] KVM: PPC: Book3S HV P9: Restore host CTRL SPR after guest exit Nicholas Piggin
2021-04-12  1:48   ` Nicholas Piggin
2021-04-12 14:06   ` Fabiano Rosas
2021-04-12 14:06     ` Fabiano Rosas
2021-04-13  1:25     ` Nicholas Piggin
2021-04-13  1:25       ` Nicholas Piggin
2021-04-12  1:48 ` [PATCH v1 02/12] KVM: PPC: Book3S HV: Nested move LPCR sanitising to sanitise_hv_regs Nicholas Piggin
2021-04-12  1:48   ` Nicholas Piggin
2021-04-12  1:48 ` [PATCH v1 03/12] KVM: PPC: Book3S HV: Add a function to filter guest LPCR bits Nicholas Piggin
2021-04-12  1:48   ` Nicholas Piggin
2021-04-12  1:48 ` [PATCH v1 04/12] KVM: PPC: Book3S HV: Disallow LPCR[AIL] to be set to 1 or 2 Nicholas Piggin
2021-04-12  1:48   ` Nicholas Piggin
2021-04-12  1:48 ` [PATCH v1 05/12] KVM: PPC: Book3S HV: Prevent radix guests setting LPCR[TC] Nicholas Piggin
2021-04-12  1:48   ` Nicholas Piggin
2021-04-12  1:48 ` [PATCH v1 06/12] KVM: PPC: Book3S HV: Remove redundant mtspr PSPB Nicholas Piggin
2021-04-12  1:48   ` Nicholas Piggin
2021-04-12  1:48 ` [PATCH v1 07/12] KVM: PPC: Book3S HV: remove unused kvmppc_h_protect argument Nicholas Piggin
2021-04-12  1:48   ` Nicholas Piggin
2021-04-12  1:48 ` [PATCH v1 08/12] KVM: PPC: Book3S HV: Fix CONFIG_SPAPR_TCE_IOMMU=n default hcalls Nicholas Piggin
2021-04-12  1:48   ` Nicholas Piggin
2021-04-12  1:48 ` [PATCH v1 09/12] powerpc/64s: Remove KVM handler support from CBE_RAS interrupts Nicholas Piggin
2021-04-12  1:48   ` Nicholas Piggin
2021-04-12  1:48 ` Nicholas Piggin [this message]
2021-04-12  1:48   ` [PATCH v1 10/12] powerpc/64s: remove KVM SKIP test from instruction breakpoint handler Nicholas Piggin
2021-04-12  1:48 ` [PATCH v1 11/12] KVM: PPC: Book3S HV: Ensure MSR[ME] is always set in guest MSR Nicholas Piggin
2021-04-12  1:48   ` Nicholas Piggin
2021-04-12  1:48 ` [PATCH v1 12/12] KVM: PPC: Book3S HV: Ensure MSR[HV] is always clear " Nicholas Piggin
2021-04-12  1:48   ` Nicholas Piggin
2021-04-16 18:34   ` Fabiano Rosas
2021-04-16 18:34     ` Fabiano Rosas
2021-04-19  3:59 ` [PATCH v1 00/12] minor KVM fixes and cleanups Michael Ellerman
2021-04-19  3:59   ` Michael Ellerman

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