[v3] powerpc/mm: Remove kvm radix prefetch workaround for Power9 DD2.2
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Message ID 20191206031722.25781-1-jniethe5@gmail.com
State New
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Series
  • [v3] powerpc/mm: Remove kvm radix prefetch workaround for Power9 DD2.2
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Commit Message

Jordan Niethe Dec. 6, 2019, 3:17 a.m. UTC
Commit a25bd72badfa ("powerpc/mm/radix: Workaround prefetch issue with
KVM") introduced a number of workarounds as coming out of a guest with
the mmu enabled would make the cpu would start running in hypervisor
state with the PID value from the guest. The cpu will then start
prefetching for the hypervisor with that PID value.

In Power9 DD2.2 the cpu behaviour was modified to fix this. When
accessing Quadrant 0 in hypervisor mode with LPID != 0 prefetching will
not be performed. This means that we can get rid of the workarounds for
Power9 DD2.2 and later revisions. Add a new cpu feature
CPU_FTR_P9_RADIX_PREFETCH_BUG to indicate if the workarounds are needed.

Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
---
v2: Use a cpu feature instead of open coding the PVR check
v3: Put parentheses around CPU_FTRS_POWER9_DD2_0 value
---
 arch/powerpc/include/asm/cputable.h      |  7 +++++--
 arch/powerpc/kernel/dt_cpu_ftrs.c        | 13 ++++++++-----
 arch/powerpc/kvm/book3s_hv_rmhandlers.S  |  2 ++
 arch/powerpc/mm/book3s64/radix_pgtable.c |  6 +++++-
 arch/powerpc/mm/book3s64/radix_tlb.c     |  3 +++
 5 files changed, 23 insertions(+), 8 deletions(-)

Comments

Paul Mackerras Jan. 17, 2020, 3:43 a.m. UTC | #1
On Fri, Dec 06, 2019 at 02:17:22PM +1100, Jordan Niethe wrote:
> Commit a25bd72badfa ("powerpc/mm/radix: Workaround prefetch issue with
> KVM") introduced a number of workarounds as coming out of a guest with
> the mmu enabled would make the cpu would start running in hypervisor
> state with the PID value from the guest. The cpu will then start
> prefetching for the hypervisor with that PID value.
> 
> In Power9 DD2.2 the cpu behaviour was modified to fix this. When
> accessing Quadrant 0 in hypervisor mode with LPID != 0 prefetching will
> not be performed. This means that we can get rid of the workarounds for
> Power9 DD2.2 and later revisions. Add a new cpu feature
> CPU_FTR_P9_RADIX_PREFETCH_BUG to indicate if the workarounds are needed.
> 
> Signed-off-by: Jordan Niethe <jniethe5@gmail.com>

Acked-by: Paul Mackerras <paulus@ozlabs.org>

Patch
diff mbox series

diff --git a/arch/powerpc/include/asm/cputable.h b/arch/powerpc/include/asm/cputable.h
index cf00ff0d121d..40a4d3c6fd99 100644
--- a/arch/powerpc/include/asm/cputable.h
+++ b/arch/powerpc/include/asm/cputable.h
@@ -212,6 +212,7 @@  static inline void cpu_feature_keys_init(void) { }
 #define CPU_FTR_P9_TLBIE_STQ_BUG	LONG_ASM_CONST(0x0000400000000000)
 #define CPU_FTR_P9_TIDR			LONG_ASM_CONST(0x0000800000000000)
 #define CPU_FTR_P9_TLBIE_ERAT_BUG	LONG_ASM_CONST(0x0001000000000000)
+#define CPU_FTR_P9_RADIX_PREFETCH_BUG	LONG_ASM_CONST(0x0002000000000000)
 
 #ifndef __ASSEMBLY__
 
@@ -459,8 +460,10 @@  static inline void cpu_feature_keys_init(void) { }
 	    CPU_FTR_DBELL | CPU_FTR_HAS_PPR | CPU_FTR_ARCH_207S | \
 	    CPU_FTR_TM_COMP | CPU_FTR_ARCH_300 | CPU_FTR_PKEY | \
 	    CPU_FTR_P9_TLBIE_STQ_BUG | CPU_FTR_P9_TLBIE_ERAT_BUG | CPU_FTR_P9_TIDR)
-#define CPU_FTRS_POWER9_DD2_0 CPU_FTRS_POWER9
-#define CPU_FTRS_POWER9_DD2_1 (CPU_FTRS_POWER9 | CPU_FTR_POWER9_DD2_1)
+#define CPU_FTRS_POWER9_DD2_0 (CPU_FTRS_POWER9 | CPU_FTR_P9_RADIX_PREFETCH_BUG)
+#define CPU_FTRS_POWER9_DD2_1 (CPU_FTRS_POWER9 | \
+			       CPU_FTR_P9_RADIX_PREFETCH_BUG | \
+			       CPU_FTR_POWER9_DD2_1)
 #define CPU_FTRS_POWER9_DD2_2 (CPU_FTRS_POWER9 | CPU_FTR_POWER9_DD2_1 | \
 			       CPU_FTR_P9_TM_HV_ASSIST | \
 			       CPU_FTR_P9_TM_XER_SO_BUG)
diff --git a/arch/powerpc/kernel/dt_cpu_ftrs.c b/arch/powerpc/kernel/dt_cpu_ftrs.c
index 180b3a5d1001..182b4047c1ef 100644
--- a/arch/powerpc/kernel/dt_cpu_ftrs.c
+++ b/arch/powerpc/kernel/dt_cpu_ftrs.c
@@ -727,17 +727,20 @@  static __init void cpufeatures_cpu_quirks(void)
 	/*
 	 * Not all quirks can be derived from the cpufeatures device tree.
 	 */
-	if ((version & 0xffffefff) == 0x004e0200)
-		; /* DD2.0 has no feature flag */
-	else if ((version & 0xffffefff) == 0x004e0201)
+	if ((version & 0xffffefff) == 0x004e0200) {
+		/* DD2.0 has no feature flag */
+		cur_cpu_spec->cpu_features |= CPU_FTR_P9_RADIX_PREFETCH_BUG;
+	} else if ((version & 0xffffefff) == 0x004e0201) {
 		cur_cpu_spec->cpu_features |= CPU_FTR_POWER9_DD2_1;
-	else if ((version & 0xffffefff) == 0x004e0202) {
+		cur_cpu_spec->cpu_features |= CPU_FTR_P9_RADIX_PREFETCH_BUG;
+	} else if ((version & 0xffffefff) == 0x004e0202) {
 		cur_cpu_spec->cpu_features |= CPU_FTR_P9_TM_HV_ASSIST;
 		cur_cpu_spec->cpu_features |= CPU_FTR_P9_TM_XER_SO_BUG;
 		cur_cpu_spec->cpu_features |= CPU_FTR_POWER9_DD2_1;
-	} else if ((version & 0xffff0000) == 0x004e0000)
+	} else if ((version & 0xffff0000) == 0x004e0000) {
 		/* DD2.1 and up have DD2_1 */
 		cur_cpu_spec->cpu_features |= CPU_FTR_POWER9_DD2_1;
+	}
 
 	if ((version & 0xffff0000) == 0x004e0000) {
 		cur_cpu_spec->cpu_features &= ~(CPU_FTR_DAWR);
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index faebcbb8c4db..72b08bb17200 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -1793,6 +1793,7 @@  END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
 	tlbsync
 	ptesync
 
+BEGIN_FTR_SECTION
 	/* Radix: Handle the case where the guest used an illegal PID */
 	LOAD_REG_ADDR(r4, mmu_base_pid)
 	lwz	r3, VCPU_GUEST_PID(r9)
@@ -1822,6 +1823,7 @@  END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
 	addi	r7,r7,0x1000
 	bdnz	1b
 	ptesync
+END_FTR_SECTION_IFSET(CPU_FTR_P9_RADIX_PREFETCH_BUG)
 
 2:
 #endif /* CONFIG_PPC_RADIX_MMU */
diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c b/arch/powerpc/mm/book3s64/radix_pgtable.c
index 6ee17d09649c..25cd2a5a6f9f 100644
--- a/arch/powerpc/mm/book3s64/radix_pgtable.c
+++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
@@ -336,7 +336,11 @@  static void __init radix_init_pgtable(void)
 	}
 
 	/* Find out how many PID bits are supported */
-	if (cpu_has_feature(CPU_FTR_HVMODE)) {
+	if (!cpu_has_feature(CPU_FTR_P9_RADIX_PREFETCH_BUG)) {
+		if (!mmu_pid_bits)
+			mmu_pid_bits = 20;
+		mmu_base_pid = 1;
+	} else if (cpu_has_feature(CPU_FTR_HVMODE)) {
 		if (!mmu_pid_bits)
 			mmu_pid_bits = 20;
 #ifdef CONFIG_KVM_BOOK3S_HV_POSSIBLE
diff --git a/arch/powerpc/mm/book3s64/radix_tlb.c b/arch/powerpc/mm/book3s64/radix_tlb.c
index 67af871190c6..d3ab36b33650 100644
--- a/arch/powerpc/mm/book3s64/radix_tlb.c
+++ b/arch/powerpc/mm/book3s64/radix_tlb.c
@@ -1221,6 +1221,9 @@  extern void radix_kvm_prefetch_workaround(struct mm_struct *mm)
 	if (unlikely(pid == MMU_NO_CONTEXT))
 		return;
 
+	if (!cpu_has_feature(CPU_FTR_P9_RADIX_PREFETCH_BUG))
+		return;
+
 	/*
 	 * If this context hasn't run on that CPU before and KVM is
 	 * around, there's a slim chance that the guest on another