On 2021-07-19 16:55, Alexandru Elisei wrote:

Hi Marc,

On 7/19/21 1:38 PM, Marc Zyngier wrote:

quoted

A number of the PMU sysregs expose reset values that are not
compliant with the architecture (set bits in the RES0 ranges,
for example).

This in turn has the effect that we need to pointlessly mask
some register fields when using them.

Let's start by making sure we don't have illegal values in the
shadow registers at reset time. This affects all the registers
that dedicate one bit per counter, the counters themselves,
PMEVTYPERn_EL0 and PMSELR_EL0.

Reported-by: Alexandre Chartre <redacted>
Reviewed-by: Alexandre Chartre <redacted>
Acked-by: Russell King (Oracle) <redacted>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/sys_regs.c | 43 
++++++++++++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index f6f126eb6ac1..96bdfa0e68b2 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c

@@ -603,6 +603,41 @@ static unsigned int pmu_visibility(const struct 

kvm_vcpu *vcpu,
 	return REG_HIDDEN;
 }

+static void reset_pmu_reg(struct kvm_vcpu *vcpu, const struct 
sys_reg_desc *r)
+{
+	u64 n, mask = BIT(ARMV8_PMU_CYCLE_IDX);
+
+	/* No PMU available, any PMU reg may UNDEF... */
+	if (!kvm_arm_support_pmu_v3())
+		return;
+
+	n = read_sysreg(pmcr_el0) >> ARMV8_PMU_PMCR_N_SHIFT;
+	n &= ARMV8_PMU_PMCR_N_MASK;
+	if (n)
+		mask |= GENMASK(n - 1, 0);

Hm... seems to be missing the cycle counter.

Check the declaration for 'mask'... :-)

         M.
-- 
Jazz is not dead. It just smells funny...

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