linux-kernel - [PATCH RFC v3 09/27] KVM: arm64: Factor SVE guest exit handling out into a function

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Message-Id: <20241220-kvm-arm64-sme-v3-9-05b018c1ffeb@kernel.org>
Date: Fri, 20 Dec 2024 16:46:34 +0000
From: Mark Brown <broonie@...nel.org>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
 Joey Gouly <joey.gouly@....com>, Catalin Marinas <catalin.marinas@....com>, 
 Suzuki K Poulose <suzuki.poulose@....com>, Will Deacon <will@...nel.org>, 
 Paolo Bonzini <pbonzini@...hat.com>, Jonathan Corbet <corbet@....net>, 
 Shuah Khan <shuah@...nel.org>
Cc: Dave Martin <Dave.Martin@....com>, Fuad Tabba <tabba@...gle.com>, 
 linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
 linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 Mark Brown <broonie@...nel.org>
Subject: [PATCH RFC v3 09/27] KVM: arm64: Factor SVE guest exit handling
 out into a function

The SVE portion of kvm_vcpu_put() is quite large, especially given the
comments required.  When we add similar handling for SME the function
will get even larger, in order to keep things managable factor the SVE
portion out of the main kvm_vcpu_put().

Signed-off-by: Mark Brown <broonie@...nel.org>
---
 arch/arm64/kvm/fpsimd.c | 67 +++++++++++++++++++++++++++----------------------
 1 file changed, 37 insertions(+), 30 deletions(-)

diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 09b65abaf9db60cc57dbc554ad2108a80c2dc46b..3c2e0b96877ac5b4f3b9d8dfa38975f11b74b60d 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -151,6 +151,41 @@ void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)
 	}
 }
 
+static void kvm_vcpu_put_sve(struct kvm_vcpu *vcpu)
+{
+	u64 zcr;
+
+	if (!vcpu_has_sve(vcpu))
+		return;
+
+	zcr = read_sysreg_el1(SYS_ZCR);
+
+	/*
+	 * If the vCPU is in the hyp context then ZCR_EL1 is loaded
+	 * with its vEL2 counterpart.
+	 */
+	__vcpu_sys_reg(vcpu, vcpu_sve_zcr_elx(vcpu)) = zcr;
+
+	/*
+	 * Restore the VL that was saved when bound to the CPU, which
+	 * is the maximum VL for the guest. Because the layout of the
+	 * data when saving the sve state depends on the VL, we need
+	 * to use a consistent (i.e., the maximum) VL.  Note that this
+	 * means that at guest exit ZCR_EL1 is not necessarily the
+	 * same as on guest entry.
+	 *
+	 * ZCR_EL2 holds the guest hypervisor's VL when running a
+	 * nested guest, which could be smaller than the max for the
+	 * vCPU. Similar to above, we first need to switch to a VL
+	 * consistent with the layout of the vCPU's SVE state. KVM
+	 * support for NV implies VHE, so using the ZCR_EL1 alias is
+	 * safe.
+	 */
+	if (!has_vhe() || (vcpu_has_nv(vcpu) && !is_hyp_ctxt(vcpu)))
+		sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
+				       SYS_ZCR_EL1);
+}
+
 /*
  * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
  * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
@@ -179,38 +214,10 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
 	}
 
 	if (guest_owns_fp_regs()) {
-		if (vcpu_has_sve(vcpu)) {
-			u64 zcr = read_sysreg_el1(SYS_ZCR);
-
-			/*
-			 * If the vCPU is in the hyp context then ZCR_EL1 is
-			 * loaded with its vEL2 counterpart.
-			 */
-			__vcpu_sys_reg(vcpu, vcpu_sve_zcr_elx(vcpu)) = zcr;
-
-			/*
-			 * Restore the VL that was saved when bound to the CPU,
-			 * which is the maximum VL for the guest. Because the
-			 * layout of the data when saving the sve state depends
-			 * on the VL, we need to use a consistent (i.e., the
-			 * maximum) VL.
-			 * Note that this means that at guest exit ZCR_EL1 is
-			 * not necessarily the same as on guest entry.
-			 *
-			 * ZCR_EL2 holds the guest hypervisor's VL when running
-			 * a nested guest, which could be smaller than the
-			 * max for the vCPU. Similar to above, we first need to
-			 * switch to a VL consistent with the layout of the
-			 * vCPU's SVE state. KVM support for NV implies VHE, so
-			 * using the ZCR_EL1 alias is safe.
-			 */
-			if (!has_vhe() || (vcpu_has_nv(vcpu) && !is_hyp_ctxt(vcpu)))
-				sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,
-						       SYS_ZCR_EL1);
-		}
+		kvm_vcpu_put_sve(vcpu);
 
 		/*
-		 * Flush (save and invalidate) the fpsimd/sve state so that if
+		 * Flush (save and invalidate) the FP state so that if
 		 * the host tries to use fpsimd/sve, it's not using stale data
 		 * from the guest.
 		 *

-- 
2.39.5