path: root/arch
diff options
authorMarc Zyngier <maz@kernel.org>2019-08-05 10:34:51 +0100
committerMarc Zyngier <maz@kernel.org>2019-08-09 08:07:24 +0100
commitc69509c70aa45a8c4954c88c629a64acf4ee4a36 (patch)
tree3d8420ab6e0a487a894040a13b3ba44c924f1ee9 /arch
parent03fdfb2690099c19160a3f2c5b77db60b3afeded (diff)
KVM: arm: Don't write junk to CP15 registers on reset
At the moment, the way we reset CP15 registers is mildly insane: We write junk to them, call the reset functions, and then check that we have something else in them. The "fun" thing is that this can happen while the guest is running (PSCI, for example). If anything in KVM has to evaluate the state of a CP15 register while junk is in there, bad thing may happen. Let's stop doing that. Instead, we track that we have called a reset function for that register, and assume that the reset function has done something. In the end, the very need of this reset check is pretty dubious, as it doesn't check everything (a lot of the CP15 reg leave outside of the cp15_regs[] array). It may well be axed in the near future. Signed-off-by: Marc Zyngier <maz@kernel.org>
Diffstat (limited to 'arch')
1 files changed, 15 insertions, 8 deletions
diff --git a/arch/arm/kvm/coproc.c b/arch/arm/kvm/coproc.c
index d2806bcff8bb..07745ee022a1 100644
--- a/arch/arm/kvm/coproc.c
+++ b/arch/arm/kvm/coproc.c
@@ -651,13 +651,22 @@ int kvm_handle_cp14_64(struct kvm_vcpu *vcpu, struct kvm_run *run)
static void reset_coproc_regs(struct kvm_vcpu *vcpu,
- const struct coproc_reg *table, size_t num)
+ const struct coproc_reg *table, size_t num,
+ unsigned long *bmap)
unsigned long i;
for (i = 0; i < num; i++)
- if (table[i].reset)
+ if (table[i].reset) {
+ int reg = table[i].reg;
table[i].reset(vcpu, &table[i]);
+ if (reg > 0 && reg < NR_CP15_REGS) {
+ set_bit(reg, bmap);
+ if (table[i].is_64bit)
+ set_bit(reg + 1, bmap);
+ }
+ }
static struct coproc_params decode_32bit_hsr(struct kvm_vcpu *vcpu)
@@ -1432,17 +1441,15 @@ void kvm_reset_coprocs(struct kvm_vcpu *vcpu)
size_t num;
const struct coproc_reg *table;
- /* Catch someone adding a register without putting in reset entry. */
- memset(vcpu->arch.ctxt.cp15, 0x42, sizeof(vcpu->arch.ctxt.cp15));
+ DECLARE_BITMAP(bmap, NR_CP15_REGS) = { 0, };
/* Generic chip reset first (so target could override). */
- reset_coproc_regs(vcpu, cp15_regs, ARRAY_SIZE(cp15_regs));
+ reset_coproc_regs(vcpu, cp15_regs, ARRAY_SIZE(cp15_regs), bmap);
table = get_target_table(vcpu->arch.target, &num);
- reset_coproc_regs(vcpu, table, num);
+ reset_coproc_regs(vcpu, table, num, bmap);
for (num = 1; num < NR_CP15_REGS; num++)
- WARN(vcpu_cp15(vcpu, num) == 0x42424242,
+ WARN(!test_bit(num, bmap),
"Didn't reset vcpu_cp15(vcpu, %zi)", num);