[PATCH] powerpc/64s: handle ISA v3.1 local copy-paste context switches

* [PATCH] powerpc/64s: handle ISA v3.1 local copy-paste context switches
@ 2020-08-25  7:55 ` Nicholas Piggin
  0 siblings, 0 replies; 6+ messages in thread
From: Nicholas Piggin @ 2020-08-25  7:55 UTC (permalink / raw)
  To: linuxppc-dev, kvm-ppc; +Cc: Nicholas Piggin

The ISA v3.1 the copy-paste facility has a new memory move functionality
which allows the copy buffer to be pasted to domestic memory (RAM) as
opposed to foreign memory (accelerator).

This means the POWER9 trick of avoiding the cp_abort on context switch if
the process had not mapped foreign memory does not work on POWER10. Do the
cp_abort unconditionally there.

KVM must also cp_abort on guest exit to prevent copy buffer state leaking
between contexts.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/kernel/process.c           | 16 +++++++++-------
 arch/powerpc/kvm/book3s_hv.c            |  7 +++++++
 arch/powerpc/kvm/book3s_hv_rmhandlers.S |  8 ++++++++
 3 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 016bd831908e..1a572c811ca5 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1250,15 +1250,17 @@ struct task_struct *__switch_to(struct task_struct *prev,
 		restore_math(current->thread.regs);
 
 		/*
-		 * The copy-paste buffer can only store into foreign real
-		 * addresses, so unprivileged processes can not see the
-		 * data or use it in any way unless they have foreign real
-		 * mappings. If the new process has the foreign real address
-		 * mappings, we must issue a cp_abort to clear any state and
-		 * prevent snooping, corruption or a covert channel.
+		 * On POWER9 the copy-paste buffer can only paste into
+		 * foreign real addresses, so unprivileged processes can not
+		 * see the data or use it in any way unless they have
+		 * foreign real mappings. If the new process has the foreign
+		 * real address mappings, we must issue a cp_abort to clear
+		 * any state and prevent snooping, corruption or a covert
+		 * channel. ISA v3.1 supports paste into local memory.
 		 */
 		if (current->mm &&
-			atomic_read(&current->mm->context.vas_windows))
+			(cpu_has_feature(CPU_FTR_ARCH_31) ||
+			atomic_read(&current->mm->context.vas_windows)))
 			asm volatile(PPC_CP_ABORT);
 	}
 #endif /* CONFIG_PPC_BOOK3S_64 */
diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
index 4ba06a2a306c..3bd3118c7633 100644
--- a/arch/powerpc/kvm/book3s_hv.c
+++ b/arch/powerpc/kvm/book3s_hv.c
@@ -3530,6 +3530,13 @@ static int kvmhv_load_hv_regs_and_go(struct kvm_vcpu *vcpu, u64 time_limit,
 	 */
 	asm volatile("eieio; tlbsync; ptesync");
 
+	/*
+	 * cp_abort is required if the processor supports local copy-paste
+	 * to clear the copy buffer that was under control of the guest.
+	 */
+	if (cpu_has_feature(CPU_FTR_ARCH_31))
+		asm volatile(PPC_CP_ABORT);
+
 	mtspr(SPRN_LPID, vcpu->kvm->arch.host_lpid);	/* restore host LPID */
 	isync();
 
diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index 799d6d0f4ead..cd9995ee8441 100644
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -1830,6 +1830,14 @@ END_FTR_SECTION_IFSET(CPU_FTR_P9_RADIX_PREFETCH_BUG)
 2:
 #endif /* CONFIG_PPC_RADIX_MMU */
 
+	/*
+	 * cp_abort is required if the processor supports local copy-paste
+	 * to clear the copy buffer that was under control of the guest.
+	 */
+BEGIN_FTR_SECTION
+	PPC_CP_ABORT
+END_FTR_SECTION_IFSET(CPU_FTR_ARCH_31)
+
 	/*
 	 * POWER7/POWER8 guest -> host partition switch code.
 	 * We don't have to lock against tlbies but we do
-- 
2.23.0


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