[PATCH 04/11] KVM: arm64: Stop save/restoring ACTLR_EL1

From: Marc Zyngier <maz@kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	kvm@vger.kernel.org, Suzuki K Poulose <suzuki.poulose@arm.com>,
	James Morse <james.morse@arm.com>,
	Andrew Scull <ascull@google.com>,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	kvmarm@lists.cs.columbia.edu,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	linux-arm-kernel@lists.infradead.org
Subject: [PATCH 04/11] KVM: arm64: Stop save/restoring ACTLR_EL1
Date: Thu, 11 Jun 2020 10:09:49 +0100	[thread overview]
Message-ID: <20200611090956.1537104-5-maz@kernel.org> (raw)
In-Reply-To: <20200611090956.1537104-1-maz@kernel.org>

From: James Morse <james.morse@arm.com>

KVM sets HCR_EL2.TACR via HCR_GUEST_FLAGS. This means ACTLR* accesses
from the guest are always trapped, and always return the value in the
sys_regs array.

The guest can't change the value of these registers, so we are
save restoring the reset value, which came from the host.

Stop save/restoring this register. Keep the storage for this register
in sys_regs[] as this is how the value is exposed to user-space,
removing it would break migration.

Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20200529150656.7339-4-james.morse@arm.com
---
 arch/arm64/kvm/hyp/sysreg-sr.c | 2 --
 arch/arm64/kvm/sys_regs.c      | 2 --
 2 files changed, 4 deletions(-)

diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
index 6d2df9fe0b5d..0d60e6ee96b2 100644
--- a/arch/arm64/kvm/hyp/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/sysreg-sr.c
@@ -39,7 +39,6 @@ static void __hyp_text __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 {
 	ctxt->sys_regs[CSSELR_EL1]	= read_sysreg(csselr_el1);
 	ctxt->sys_regs[SCTLR_EL1]	= read_sysreg_el1(SYS_SCTLR);
-	ctxt->sys_regs[ACTLR_EL1]	= read_sysreg(actlr_el1);
 	ctxt->sys_regs[CPACR_EL1]	= read_sysreg_el1(SYS_CPACR);
 	ctxt->sys_regs[TTBR0_EL1]	= read_sysreg_el1(SYS_TTBR0);
 	ctxt->sys_regs[TTBR1_EL1]	= read_sysreg_el1(SYS_TTBR1);
@@ -122,7 +121,6 @@ static void __hyp_text __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
 		isb();
 	}
 
-	write_sysreg(ctxt->sys_regs[ACTLR_EL1],		actlr_el1);
 	write_sysreg_el1(ctxt->sys_regs[CPACR_EL1],	SYS_CPACR);
 	write_sysreg_el1(ctxt->sys_regs[TTBR0_EL1],	SYS_TTBR0);
 	write_sysreg_el1(ctxt->sys_regs[TTBR1_EL1],	SYS_TTBR1);
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index 12f8d57a3cb8..dfb966f3863a 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -78,7 +78,6 @@ static bool __vcpu_read_sys_reg_from_cpu(int reg, u64 *val)
 	switch (reg) {
 	case CSSELR_EL1:	*val = read_sysreg_s(SYS_CSSELR_EL1);	break;
 	case SCTLR_EL1:		*val = read_sysreg_s(SYS_SCTLR_EL12);	break;
-	case ACTLR_EL1:		*val = read_sysreg_s(SYS_ACTLR_EL1);	break;
 	case CPACR_EL1:		*val = read_sysreg_s(SYS_CPACR_EL12);	break;
 	case TTBR0_EL1:		*val = read_sysreg_s(SYS_TTBR0_EL12);	break;
 	case TTBR1_EL1:		*val = read_sysreg_s(SYS_TTBR1_EL12);	break;
@@ -118,7 +117,6 @@ static bool __vcpu_write_sys_reg_to_cpu(u64 val, int reg)
 	switch (reg) {
 	case CSSELR_EL1:	write_sysreg_s(val, SYS_CSSELR_EL1);	break;
 	case SCTLR_EL1:		write_sysreg_s(val, SYS_SCTLR_EL12);	break;
-	case ACTLR_EL1:		write_sysreg_s(val, SYS_ACTLR_EL1);	break;
 	case CPACR_EL1:		write_sysreg_s(val, SYS_CPACR_EL12);	break;
 	case TTBR0_EL1:		write_sysreg_s(val, SYS_TTBR0_EL12);	break;
 	case TTBR1_EL1:		write_sysreg_s(val, SYS_TTBR1_EL12);	break;
-- 
2.26.2


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