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From: Paul Mackerras <paulus@samba.org>
To: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org
Cc: Alexander Graf <agraf@suse.de>, Paul Mackerras <paulus@samba.org>
Subject: [PATCH 7/8] KVM: PPC: Book3S HV: Fix decrementer timeouts with non-zero TB offset
Date: Tue, 25 Mar 2014 10:47:07 +1100	[thread overview]
Message-ID: <1395704828-20180-8-git-send-email-paulus@samba.org> (raw)
In-Reply-To: <1395704828-20180-1-git-send-email-paulus@samba.org>

Commit c7699822bc21 ("KVM: PPC: Book3S HV: Make physical thread 0 do
the MMU switching") reordered the guest entry/exit code so that most
of the guest register save/restore code happened in guest MMU context.
A side effect of that is that the timebase still contains the guest
timebase value at the point where we compute and use vcpu->arch.dec_expires,
and therefore that is now a guest timebase value rather than a host
timebase value.  That in turn means that the timeouts computed in
kvmppc_set_timer() are wrong if the timebase offset for the guest is
non-zero.  The consequence of that is things such as "sleep 1" in a
guest after migration may sleep for much longer than they should.

This fixes the problem by converting between guest and host timebase
values as necessary, by adding or subtracting the timebase offset.
This also fixes an incorrect comment.

Signed-off-by: Paul Mackerras <paulus@samba.org>
---
 arch/powerpc/kvm/book3s_hv_rmhandlers.S | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 6c8dca7..0e6d9e5 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -833,6 +833,10 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S)
 	 * Set the decrementer to the guest decrementer.
 	 */
 	ld	r8,VCPU_DEC_EXPIRES(r4)
+	/* r8 is a host timebase value here, convert to guest TB */
+	ld	r5,HSTATE_KVM_VCORE(r13)
+	ld	r6,VCORE_TB_OFFSET(r5)
+	add	r8,r8,r6
 	mftb	r7
 	subf	r3,r7,r8
 	mtspr	SPRN_DEC,r3
@@ -1196,6 +1200,10 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_201)
 	mftb	r6
 	extsw	r5,r5
 	add	r5,r5,r6
+	/* r5 is a guest timebase value here, convert to host TB */
+	ld	r3,HSTATE_KVM_VCORE(r13)
+	ld	r4,VCORE_TB_OFFSET(r3)
+	subf	r5,r4,r5
 	std	r5,VCPU_DEC_EXPIRES(r9)
 
 BEGIN_FTR_SECTION
@@ -1471,7 +1479,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
 	ld	r8,VCORE_TB_OFFSET(r5)
 	cmpdi	r8,0
 	beq	17f
-	mftb	r6			/* current host timebase */
+	mftb	r6			/* current guest timebase */
 	subf	r8,r8,r6
 	mtspr	SPRN_TBU40,r8		/* update upper 40 bits */
 	mftb	r7			/* check if lower 24 bits overflowed */
-- 
1.9.rc1

WARNING: multiple messages have this Message-ID (diff)
From: Paul Mackerras <paulus@samba.org>
To: kvm@vger.kernel.org, kvm-ppc@vger.kernel.org
Cc: Alexander Graf <agraf@suse.de>, Paul Mackerras <paulus@samba.org>
Subject: [PATCH 7/8] KVM: PPC: Book3S HV: Fix decrementer timeouts with non-zero TB offset
Date: Mon, 24 Mar 2014 23:47:07 +0000	[thread overview]
Message-ID: <1395704828-20180-8-git-send-email-paulus@samba.org> (raw)
In-Reply-To: <1395704828-20180-1-git-send-email-paulus@samba.org>

Commit c7699822bc21 ("KVM: PPC: Book3S HV: Make physical thread 0 do
the MMU switching") reordered the guest entry/exit code so that most
of the guest register save/restore code happened in guest MMU context.
A side effect of that is that the timebase still contains the guest
timebase value at the point where we compute and use vcpu->arch.dec_expires,
and therefore that is now a guest timebase value rather than a host
timebase value.  That in turn means that the timeouts computed in
kvmppc_set_timer() are wrong if the timebase offset for the guest is
non-zero.  The consequence of that is things such as "sleep 1" in a
guest after migration may sleep for much longer than they should.

This fixes the problem by converting between guest and host timebase
values as necessary, by adding or subtracting the timebase offset.
This also fixes an incorrect comment.

Signed-off-by: Paul Mackerras <paulus@samba.org>
---
 arch/powerpc/kvm/book3s_hv_rmhandlers.S | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 6c8dca7..0e6d9e5 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -833,6 +833,10 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S)
 	 * Set the decrementer to the guest decrementer.
 	 */
 	ld	r8,VCPU_DEC_EXPIRES(r4)
+	/* r8 is a host timebase value here, convert to guest TB */
+	ld	r5,HSTATE_KVM_VCORE(r13)
+	ld	r6,VCORE_TB_OFFSET(r5)
+	add	r8,r8,r6
 	mftb	r7
 	subf	r3,r7,r8
 	mtspr	SPRN_DEC,r3
@@ -1196,6 +1200,10 @@ END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_201)
 	mftb	r6
 	extsw	r5,r5
 	add	r5,r5,r6
+	/* r5 is a guest timebase value here, convert to host TB */
+	ld	r3,HSTATE_KVM_VCORE(r13)
+	ld	r4,VCORE_TB_OFFSET(r3)
+	subf	r5,r4,r5
 	std	r5,VCPU_DEC_EXPIRES(r9)
 
 BEGIN_FTR_SECTION
@@ -1471,7 +1479,7 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_207S)
 	ld	r8,VCORE_TB_OFFSET(r5)
 	cmpdi	r8,0
 	beq	17f
-	mftb	r6			/* current host timebase */
+	mftb	r6			/* current guest timebase */
 	subf	r8,r8,r6
 	mtspr	SPRN_TBU40,r8		/* update upper 40 bits */
 	mftb	r7			/* check if lower 24 bits overflowed */
-- 
1.9.rc1


  parent reply	other threads:[~2014-03-24 23:47 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-03-24 23:47 [PATCH 0/8] PPC Book 3S HV-mode KVM updates for 3.15 Paul Mackerras
2014-03-24 23:47 ` Paul Mackerras
2014-03-24 23:47 ` [PATCH 1/8] KVM: PPC: Book3S HV: Fix KVM hang with CONFIG_KVM_XICS=n Paul Mackerras
2014-03-24 23:47   ` Paul Mackerras
2014-03-24 23:47 ` [PATCH 2/8] KVM: PPC: Book3S HV: Add transactional memory support Paul Mackerras
2014-03-24 23:47   ` Paul Mackerras
2014-03-24 23:47 ` [PATCH 3/8] KVM: PPC: Book3S HV: Add get/set_one_reg for new TM state Paul Mackerras
2014-03-24 23:47   ` Paul Mackerras
2014-03-28  5:40   ` [PATCH 1/2] KVM: PPC: Book3S HV: Make TM avoid program check Michael Neuling
2014-03-28  5:40     ` Michael Neuling
2014-03-28  5:40     ` [PATCH 2/2] KVM: PPC: Book3S HV: Add branch label Michael Neuling
2014-03-28  5:40       ` Michael Neuling
2014-03-28 11:08     ` [PATCH 1/2] KVM: PPC: Book3S HV: Make TM avoid program check Paul Mackerras
2014-03-28 11:08       ` Paul Mackerras
2014-03-28 12:14       ` Paolo Bonzini
2014-03-28 12:14         ` Paolo Bonzini
2014-03-24 23:47 ` [PATCH 4/8] KVM: PPC: Book3S: Trim top 4 bits of physical address in RTAS code Paul Mackerras
2014-03-24 23:47   ` Paul Mackerras
2014-03-24 23:47 ` [PATCH 5/8] KVM: PPC: Book3S HV: Return ENODEV error rather than EIO Paul Mackerras
2014-03-24 23:47   ` Paul Mackerras
2014-03-24 23:47 ` [PATCH 6/8] KVM: PPC: Book3S HV: Don't use kvm_memslots() in real mode Paul Mackerras
2014-03-24 23:47   ` Paul Mackerras
2014-03-24 23:47 ` Paul Mackerras [this message]
2014-03-24 23:47   ` [PATCH 7/8] KVM: PPC: Book3S HV: Fix decrementer timeouts with non-zero TB offset Paul Mackerras
2014-03-24 23:47 ` [PATCH 8/8] KVM: PPC: Book3S HV: Save/restore host PMU registers that are new in POWER8 Paul Mackerras
2014-03-24 23:47   ` Paul Mackerras
2014-03-25  1:39 ` [PATCH 0/8] PPC Book 3S HV-mode KVM updates for 3.15 Scott Wood
2014-03-25  1:39   ` Scott Wood

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