KVM: arm64: Get rid of __kvm_get_mdcr_el2() and related warts

KVM caches MDCR_EL2 on a per-CPU basis in order to preserve the
configuration of MDCR_EL2.HPMN while running a guest. This is a bit
gross, since we're relying on some baked configuration rather than the
hardware definition of implemented counters.

Discover the number of implemented counters by reading PMCR_EL0.N
instead. This works because:

 - In VHE the kernel runs at EL2, and N always returns the number of
   counters implemented in hardware

 - In {n,h}VHE, the EL2 setup code programs MDCR_EL2.HPMN with the EL2
   view of PMCR_EL0.N for the host

Lastly, avoid traps under nested virtualization by saving PMCR_EL0.N in
host data.

Tested-by: James Clark <james.clark@linaro.org>
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20241219224116.3941496-3-oliver.upton@linux.dev
Signed-off-by: Marc Zyngier <maz@kernel.org>

diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index ca259034431353dc8ec56c0f9c66fbc13fbd7704..063185c202ce1c4a2185cbe6304682d724f30bde 100644 (file)
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -53,8 +53,7 @@
 enum __kvm_host_smccc_func {
        /* Hypercalls available only prior to pKVM finalisation */
        /* __KVM_HOST_SMCCC_FUNC___kvm_hyp_init */
-       __KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2 = __KVM_HOST_SMCCC_FUNC___kvm_hyp_init + 1,
-       __KVM_HOST_SMCCC_FUNC___pkvm_init,
+       __KVM_HOST_SMCCC_FUNC___pkvm_init = __KVM_HOST_SMCCC_FUNC___kvm_hyp_init + 1,
        __KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping,
        __KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector,
        __KVM_HOST_SMCCC_FUNC___kvm_enable_ssbs,
@@ -247,8 +246,6 @@ extern void __kvm_adjust_pc(struct kvm_vcpu *vcpu);
 extern u64 __vgic_v3_get_gic_config(void);
 extern void __vgic_v3_init_lrs(void);
 
-extern u64 __kvm_get_mdcr_el2(void);
-
 #define __KVM_EXTABLE(from, to)                                                \
        "       .pushsection    __kvm_ex_table, \"a\"\n"                \
        "       .align          3\n"                                    \

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index e18e9244d17a4f7742729e31481680254617bac8..064f5dfca7f42d4ef5860928c8edf7eb711dcb77 100644 (file)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -642,7 +642,7 @@ struct kvm_host_data {
         * host_debug_state contains the host registers which are
         * saved and restored during world switches.
         */
-        struct {
+       struct {
                /* {Break,watch}point registers */
                struct kvm_guest_debug_arch regs;
                /* Statistical profiling extension */
@@ -652,6 +652,9 @@ struct kvm_host_data {
                /* Values of trap registers for the host before guest entry. */
                u64 mdcr_el2;
        } host_debug_state;
+
+       /* Number of programmable event counters (PMCR_EL0.N) for this CPU */
+       unsigned int nr_event_counters;
 };
 
 struct kvm_host_psci_config {
@@ -1332,7 +1335,7 @@ static inline bool kvm_system_needs_idmapped_vectors(void)
 
 static inline void kvm_arch_sync_events(struct kvm *kvm) {}
 
-void kvm_arm_init_debug(void);
+void kvm_init_host_debug_data(void);
 void kvm_arm_vcpu_init_debug(struct kvm_vcpu *vcpu);
 void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
 void kvm_arm_clear_debug(struct kvm_vcpu *vcpu);

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index a102c3aebdbc419fe94a0f973eb2b3f06f0ba698..ab1bf9ccf385e97816e29a7273b91d440c076abd 100644 (file)
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -2109,6 +2109,7 @@ static void cpu_set_hyp_vector(void)
 static void cpu_hyp_init_context(void)
 {
        kvm_init_host_cpu_context(host_data_ptr(host_ctxt));
+       kvm_init_host_debug_data();
 
        if (!is_kernel_in_hyp_mode())
                cpu_init_hyp_mode();
@@ -2117,7 +2118,6 @@ static void cpu_hyp_init_context(void)
 static void cpu_hyp_init_features(void)
 {
        cpu_set_hyp_vector();
-       kvm_arm_init_debug();
 
        if (is_kernel_in_hyp_mode())
                kvm_timer_init_vhe();

diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
index 587e9eb4372e2bf8e0d68381a2f2611a771daecb..d8ea6fe6a2a226a4f5840a26d8ae4808dae83934 100644 (file)
--- a/arch/arm64/kvm/debug.c
+++ b/arch/arm64/kvm/debug.c
@@ -16,8 +16,6 @@
 
 #include "trace.h"
 
-static DEFINE_PER_CPU(u64, mdcr_el2);
-
 /*
  * save/restore_guest_debug_regs
  *
@@ -60,21 +58,6 @@ static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
                *vcpu_cpsr(vcpu) &= ~DBG_SPSR_SS;
 }
 
-/**
- * kvm_arm_init_debug - grab what we need for debug
- *
- * Currently the sole task of this function is to retrieve the initial
- * value of mdcr_el2 so we can preserve MDCR_EL2.HPMN which has
- * presumably been set-up by some knowledgeable bootcode.
- *
- * It is called once per-cpu during CPU hyp initialisation.
- */
-
-void kvm_arm_init_debug(void)
-{
-       __this_cpu_write(mdcr_el2, kvm_call_hyp_ret(__kvm_get_mdcr_el2));
-}
-
 /**
  * kvm_arm_setup_mdcr_el2 - configure vcpu mdcr_el2 value
  *
@@ -94,7 +77,8 @@ static void kvm_arm_setup_mdcr_el2(struct kvm_vcpu *vcpu)
         * This also clears MDCR_EL2_E2PB_MASK and MDCR_EL2_E2TB_MASK
         * to disable guest access to the profiling and trace buffers
         */
-       vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & MDCR_EL2_HPMN_MASK;
+       vcpu->arch.mdcr_el2 = FIELD_PREP(MDCR_EL2_HPMN,
+                                        *host_data_ptr(nr_event_counters));
        vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM |
                                MDCR_EL2_TPMS |
                                MDCR_EL2_TTRF |
@@ -338,3 +322,12 @@ void kvm_arch_vcpu_put_debug_state_flags(struct kvm_vcpu *vcpu)
        vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_SPE);
        vcpu_clear_flag(vcpu, DEBUG_STATE_SAVE_TRBE);
 }
+
+void kvm_init_host_debug_data(void)
+{
+       u64 dfr0 = read_sysreg(id_aa64dfr0_el1);
+
+       if (cpuid_feature_extract_signed_field(dfr0, ID_AA64DFR0_EL1_PMUVer_SHIFT) > 0)
+               *host_data_ptr(nr_event_counters) = FIELD_GET(ARMV8_PMU_PMCR_N,
+                                                             read_sysreg(pmcr_el0));
+}

diff --git a/arch/arm64/kvm/hyp/nvhe/debug-sr.c b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
index 53efda0235cfe00709ccc89ba9591bb17d672225..1e2a26d0196e52bb9b5c11aa95fe5d4fd171f0e0 100644 (file)
--- a/arch/arm64/kvm/hyp/nvhe/debug-sr.c
+++ b/arch/arm64/kvm/hyp/nvhe/debug-sr.c
@@ -106,8 +106,3 @@ void __debug_switch_to_host(struct kvm_vcpu *vcpu)
 {
        __debug_switch_to_host_common(vcpu);
 }
-
-u64 __kvm_get_mdcr_el2(void)
-{
-       return read_sysreg(mdcr_el2);
-}

diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index 6aa0b13d86e581a36ed529bcd932498045d2d6df..16f5da3a884a47fc400e9bc847c69e4dc90c40c6 100644 (file)
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -264,11 +264,6 @@ static void handle___vgic_v3_init_lrs(struct kvm_cpu_context *host_ctxt)
        __vgic_v3_init_lrs();
 }
 
-static void handle___kvm_get_mdcr_el2(struct kvm_cpu_context *host_ctxt)
-{
-       cpu_reg(host_ctxt, 1) = __kvm_get_mdcr_el2();
-}
-
 static void handle___vgic_v3_save_vmcr_aprs(struct kvm_cpu_context *host_ctxt)
 {
        DECLARE_REG(struct vgic_v3_cpu_if *, cpu_if, host_ctxt, 1);
@@ -384,7 +379,6 @@ typedef void (*hcall_t)(struct kvm_cpu_context *);
 
 static const hcall_t host_hcall[] = {
        /* ___kvm_hyp_init */
-       HANDLE_FUNC(__kvm_get_mdcr_el2),
        HANDLE_FUNC(__pkvm_init),
        HANDLE_FUNC(__pkvm_create_private_mapping),
        HANDLE_FUNC(__pkvm_cpu_set_vector),

diff --git a/arch/arm64/kvm/hyp/vhe/debug-sr.c b/arch/arm64/kvm/hyp/vhe/debug-sr.c
index 289689b2682deece89d7dd0c738b3fd3ed80f78a..0100339b09e0927789b58bf8bce4650791bf99bf 100644 (file)
--- a/arch/arm64/kvm/hyp/vhe/debug-sr.c
+++ b/arch/arm64/kvm/hyp/vhe/debug-sr.c
@@ -19,8 +19,3 @@ void __debug_switch_to_host(struct kvm_vcpu *vcpu)
 {
        __debug_switch_to_host_common(vcpu);
 }
-
-u64 __kvm_get_mdcr_el2(void)
-{
-       return read_sysreg(mdcr_el2);
-}