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From: Andrew Scull <ascull@google.com>
To: kvmarm@lists.cs.columbia.edu
Cc: kernel-team@android.com, maz@kernel.org, catalin.marinas@arm.com,
	will@kernel.org, Dave.Martin@arm.com
Subject: [PATCH 02/10] KVM: arm64: Synchronize vcpu FPSIMD in the host
Date: Thu,  4 Mar 2021 11:54:45 +0000	[thread overview]
Message-ID: <20210304115454.3597879-3-ascull@google.com> (raw)
In-Reply-To: <20210304115454.3597879-1-ascull@google.com>

Check the task's state about FP in the host and update the vcpu flags
before calling into hyp. This keeps the synchronization symmetrical
around the call into hyp.

kvm_arch_vcpu_ctxsync_fp() is renamed to kvm_arch_vcpu_sync_fp_after_hyp()
so that its name can pair with the new kvm_arch_vcpu_sync_fp_before_hyp().

If the system doesn't support FPSIMD, avoid setting any of the vcpu's
FPSIMD flags to match the previous behavior.

Signed-off-by: Andrew Scull <ascull@google.com>
Cc: Dave Martin <Dave.Martin@arm.com>
---
 arch/arm64/include/asm/kvm_host.h       |  3 ++-
 arch/arm64/kvm/arm.c                    |  4 +++-
 arch/arm64/kvm/fpsimd.c                 | 26 ++++++++++++++++++++++++-
 arch/arm64/kvm/hyp/include/hyp/switch.h | 19 ------------------
 arch/arm64/kvm/hyp/nvhe/switch.c        |  3 +--
 arch/arm64/kvm/hyp/vhe/switch.c         |  3 +--
 6 files changed, 32 insertions(+), 26 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 6b33f720ce9c..f6a478d3a902 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -726,7 +726,8 @@ int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
 /* Guest/host FPSIMD coordination helpers */
 int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
-void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu);
+void kvm_arch_vcpu_sync_fp_before_hyp(struct kvm_vcpu *vcpu);
+void kvm_arch_vcpu_sync_fp_after_hyp(struct kvm_vcpu *vcpu);
 void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
 
 static inline bool kvm_pmu_counter_deferred(struct perf_event_attr *attr)
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index fc4c95dd2d26..26ccc369cf11 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -738,6 +738,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 
 		local_irq_disable();
 
+		kvm_arch_vcpu_sync_fp_before_hyp(vcpu);
+
 		kvm_vgic_flush_hwstate(vcpu);
 
 		/*
@@ -825,7 +827,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
 		if (static_branch_unlikely(&userspace_irqchip_in_use))
 			kvm_timer_sync_user(vcpu);
 
-		kvm_arch_vcpu_ctxsync_fp(vcpu);
+		kvm_arch_vcpu_sync_fp_after_hyp(vcpu);
 
 		/*
 		 * We may have taken a host interrupt in HYP mode (ie
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 3e081d556e81..0c5e79be34d5 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -63,8 +63,13 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
 	BUG_ON(!current->mm);
 
 	vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
+			      KVM_ARM64_FP_HOST |
 			      KVM_ARM64_HOST_SVE_IN_USE |
 			      KVM_ARM64_HOST_SVE_ENABLED);
+
+	if (!system_supports_fpsimd())
+		return;
+
 	vcpu->arch.flags |= KVM_ARM64_FP_HOST;
 
 	if (test_thread_flag(TIF_SVE))
@@ -74,13 +79,32 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
 		vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED;
 }
 
+
+/*
+ * If TIF_FOREIGN_FPSTATE is set, the FPSIMD regs do not contain the state of
+ * current or the guest. However, the state will have been saved where it was
+ * needed. This means the guest's state will have to be loaded if it is needed,
+ * without saving the FPSIMD regs.
+ */
+void kvm_arch_vcpu_sync_fp_before_hyp(struct kvm_vcpu *vcpu)
+{
+	WARN_ON_ONCE(!irqs_disabled());
+
+	if (!system_supports_fpsimd())
+		return;
+
+	if (test_thread_flag(TIF_FOREIGN_FPSTATE))
+		vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
+				      KVM_ARM64_FP_HOST);
+}
+
 /*
  * If the guest FPSIMD state was loaded, update the host's context
  * tracking data mark the CPU FPSIMD regs as dirty and belonging to vcpu
  * so that they will be written back if the kernel clobbers them due to
  * kernel-mode NEON before re-entry into the guest.
  */
-void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
+void kvm_arch_vcpu_sync_fp_after_hyp(struct kvm_vcpu *vcpu)
 {
 	WARN_ON_ONCE(!irqs_disabled());
 
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 54f4860cd87c..8eb1f87f9119 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -28,31 +28,12 @@
 #include <asm/fpsimd.h>
 #include <asm/debug-monitors.h>
 #include <asm/processor.h>
-#include <asm/thread_info.h>
 
 extern const char __hyp_panic_string[];
 
 extern struct exception_table_entry __start___kvm_ex_table;
 extern struct exception_table_entry __stop___kvm_ex_table;
 
-/* Check whether the FP regs were dirtied while in the host-side run loop: */
-static inline bool update_fp_enabled(struct kvm_vcpu *vcpu)
-{
-	/*
-	 * When the system doesn't support FP/SIMD, we cannot rely on
-	 * the _TIF_FOREIGN_FPSTATE flag. However, we always inject an
-	 * abort on the very first access to FP and thus we should never
-	 * see KVM_ARM64_FP_ENABLED. For added safety, make sure we always
-	 * trap the accesses.
-	 */
-	if (!system_supports_fpsimd() ||
-	    vcpu->arch.host_thread_info->flags & _TIF_FOREIGN_FPSTATE)
-		vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED |
-				      KVM_ARM64_FP_HOST);
-
-	return !!(vcpu->arch.flags & KVM_ARM64_FP_ENABLED);
-}
-
 /* Save the 32-bit only FPSIMD system register state */
 static inline void __fpsimd_save_fpexc32(struct kvm_vcpu *vcpu)
 {
diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
index f3d0e9eca56c..6fc1e0a5adaa 100644
--- a/arch/arm64/kvm/hyp/nvhe/switch.c
+++ b/arch/arm64/kvm/hyp/nvhe/switch.c
@@ -26,7 +26,6 @@
 #include <asm/fpsimd.h>
 #include <asm/debug-monitors.h>
 #include <asm/processor.h>
-#include <asm/thread_info.h>
 
 /* Non-VHE specific context */
 DEFINE_PER_CPU(struct kvm_host_data, kvm_host_data);
@@ -42,7 +41,7 @@ static void __activate_traps(struct kvm_vcpu *vcpu)
 
 	val = CPTR_EL2_DEFAULT;
 	val |= CPTR_EL2_TTA | CPTR_EL2_TZ | CPTR_EL2_TAM;
-	if (!update_fp_enabled(vcpu)) {
+	if (!(vcpu->arch.flags & KVM_ARM64_FP_ENABLED)) {
 		val |= CPTR_EL2_TFP;
 		__activate_traps_fpsimd32(vcpu);
 	}
diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index af8e940d0f03..f6f60a537b3e 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -25,7 +25,6 @@
 #include <asm/fpsimd.h>
 #include <asm/debug-monitors.h>
 #include <asm/processor.h>
-#include <asm/thread_info.h>
 
 const char __hyp_panic_string[] = "HYP panic:\nPS:%08llx PC:%016llx ESR:%08llx\nFAR:%016llx HPFAR:%016llx PAR:%016llx\nVCPU:%p\n";
 
@@ -55,7 +54,7 @@ static void __activate_traps(struct kvm_vcpu *vcpu)
 
 	val |= CPTR_EL2_TAM;
 
-	if (update_fp_enabled(vcpu)) {
+	if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
 		if (vcpu_has_sve(vcpu))
 			val |= CPACR_EL1_ZEN;
 	} else {
-- 
2.30.1.766.gb4fecdf3b7-goog

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  parent reply	other threads:[~2021-03-04 11:55 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-04 11:54 [PATCH 00/10] FPSIMD restore bypass and protecting Andrew Scull
2021-03-04 11:54 ` [PATCH 01/10] KVM: arm64: Leave KVM_ARM64_DEBUG_DIRTY updates to the host Andrew Scull
2021-03-04 11:54 ` Andrew Scull [this message]
2021-03-04 11:54 ` [PATCH 03/10] KVM: arm64: Unmap host task thread flags from hyp Andrew Scull
2021-03-04 11:54 ` [PATCH 04/10] KVM: arm64: Support smp_processor_id() in nVHE hyp Andrew Scull
2021-03-11 10:35   ` Quentin Perret
2021-03-12 11:20     ` Andrew Scull
2021-03-12 11:27       ` Andrew Scull
2021-03-04 11:54 ` [PATCH 05/10] KVM: arm64: Track where vcpu FP state was last loaded Andrew Scull
2021-03-11 10:37   ` Quentin Perret
2021-03-11 10:40     ` Quentin Perret
2021-03-04 11:54 ` [PATCH 06/10] KVM: arm64: Avoid needlessly reloading guest FP state Andrew Scull
2021-03-04 11:54 ` [PATCH 07/10] KVM: arm64: Separate host and hyp vcpu FP flags Andrew Scull
2021-03-04 11:54 ` [PATCH 08/10] KVM: arm64: Pass the arch run struct explicitly Andrew Scull
2021-03-04 11:54 ` [PATCH 09/10] KVM: arm64: Use hyp-private run struct in protected mode Andrew Scull
2021-03-04 11:54 ` [PATCH 10/10] RFC: KVM: arm64: Manage FPSIMD state at EL2 for protected vCPUs Andrew Scull

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