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[02/11] KVM: arm64: Stop writing aarch32's CSSELR into ACTLR

Message ID 20200611090956.1537104-3-maz@kernel.org
State New
Headers show
Series None | expand

Commit Message

Marc Zyngier June 11, 2020, 9:09 a.m. UTC 
From: James Morse <james.morse@arm.com>

aarch32 has pairs of registers to access the high and low parts of 64bit
registers. KVM has a union of 64bit sys_regs[] and 32bit copro[]. The
32bit accessors read the high or low part of the 64bit sys_reg[] value
through the union.

Both sys_reg_descs[] and cp15_regs[] list access_csselr() as the accessor
for CSSELR{,_EL1}. access_csselr() is only aware of the 64bit sys_regs[],
and expects r->reg to be 'CSSELR_EL1' in the enum, index 2 of the 64bit
array.

cp15_regs[] uses the 32bit copro[] alias of sys_regs[]. Here CSSELR is
c0_CSSELR which is the same location in sys_reg[]. r->reg is 'c0_CSSELR',
index 4 in the 32bit array.

access_csselr() uses the 32bit r->reg value to access the 64bit array,
so reads and write the wrong value. sys_regs[4], is ACTLR_EL1, which
is subsequently save/restored when we enter the guest.

ACTLR_EL1 is supposed to be read-only for the guest. This register
only affects execution at EL1, and the host's value is restored before
we return to host EL1.

Convert the 32bit register index back to the 64bit version.

Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20200529150656.7339-2-james.morse@arm.com
---
 arch/arm64/kvm/sys_regs.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)
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Patch

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index ad1d57501d6d..12f8d57a3cb8 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -1319,10 +1319,16 @@  static bool access_clidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 static bool access_csselr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
 			  const struct sys_reg_desc *r)
 {
+	int reg = r->reg;
+
+	/* See the 32bit mapping in kvm_host.h */
+	if (p->is_aarch32)
+		reg = r->reg / 2;
+
 	if (p->is_write)
-		vcpu_write_sys_reg(vcpu, p->regval, r->reg);
+		vcpu_write_sys_reg(vcpu, p->regval, reg);
 	else
-		p->regval = vcpu_read_sys_reg(vcpu, r->reg);
+		p->regval = vcpu_read_sys_reg(vcpu, reg);
 	return true;
 }