arm/arm64: KVM: Statically configure the host's view of MPIDR

We currently eagerly save/restore MPIDR. It turns out to be
slightly pointless:
- On the host, this value is known as soon as we're scheduled on a
  physical CPU
- In the guest, this value cannot change, as it is set by KVM
  (and this is a read-only register)

The result of the above is that we can perfectly avoid the eager
saving of MPIDR_EL1, and only keep the restore. We just have
to setup the host contexts appropriately at boot time.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index 4b6193f2f0f6f939b3fcd7c50eb0d5bdbdf8b0a8..43e343e00fb88ab4c290f50503deb3b437026564 100644 (file)
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -26,6 +26,7 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmio.h>
 #include <asm/fpstate.h>
+#include <asm/smp_plat.h>
 #include <kvm/arm_arch_timer.h>
 
 #define __KVM_HAVE_ARCH_INTC_INITIALIZED
@@ -147,6 +148,13 @@ struct kvm_cpu_context {
 
 typedef struct kvm_cpu_context kvm_cpu_context_t;
 
+static inline void kvm_init_host_cpu_context(kvm_cpu_context_t *cpu_ctxt,
+                                            int cpu)
+{
+       /* The host's MPIDR is immutable, so let's set it up at boot time */
+       cpu_ctxt->cp15[c0_MPIDR] = cpu_logical_map(cpu);
+}
+
 struct kvm_vcpu_arch {
        struct kvm_cpu_context ctxt;
 

diff --git a/arch/arm/kvm/hyp/cp15-sr.c b/arch/arm/kvm/hyp/cp15-sr.c
index c4782812714cf4cbdbd532c8b975cd5cd20ee4cf..8bf895ec6e04231f9849ef3ca4bf88d45eb3f74f 100644 (file)
--- a/arch/arm/kvm/hyp/cp15-sr.c
+++ b/arch/arm/kvm/hyp/cp15-sr.c
@@ -27,7 +27,6 @@ static u64 *cp15_64(struct kvm_cpu_context *ctxt, int idx)
 
 void __hyp_text __sysreg_save_state(struct kvm_cpu_context *ctxt)
 {
-       ctxt->cp15[c0_MPIDR]            = read_sysreg(VMPIDR);
        ctxt->cp15[c0_CSSELR]           = read_sysreg(CSSELR);
        ctxt->cp15[c1_SCTLR]            = read_sysreg(SCTLR);
        ctxt->cp15[c1_CPACR]            = read_sysreg(CPACR);

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 8b7702bdb219ab84115ad97018ed644d5ce417de..f497bb31031ffed16f99a5e5b6138b880533adf2 100644 (file)
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -30,6 +30,7 @@
 #include <asm/kvm.h>
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmio.h>
+#include <asm/smp_plat.h>
 #include <asm/thread_info.h>
 
 #define __KVM_HAVE_ARCH_INTC_INITIALIZED
@@ -418,6 +419,13 @@ struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
 
 DECLARE_PER_CPU(kvm_cpu_context_t, kvm_host_cpu_state);
 
+static inline void kvm_init_host_cpu_context(kvm_cpu_context_t *cpu_ctxt,
+                                            int cpu)
+{
+       /* The host's MPIDR is immutable, so let's set it up at boot time */
+       cpu_ctxt->sys_regs[MPIDR_EL1] = cpu_logical_map(cpu);
+}
+
 void __kvm_enable_ssbs(void);
 
 static inline void __cpu_init_hyp_mode(phys_addr_t pgd_ptr,

diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
index 68d6f7c3b237dc1713fa36bc55d4a27fef2e5949..2498f86defcbbbba5c70a24ccf51180bca7afa59 100644 (file)
--- a/arch/arm64/kvm/hyp/sysreg-sr.c
+++ b/arch/arm64/kvm/hyp/sysreg-sr.c
@@ -52,7 +52,6 @@ static void __hyp_text __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
 
 static void __hyp_text __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
 {
-       ctxt->sys_regs[MPIDR_EL1]       = read_sysreg(vmpidr_el2);
        ctxt->sys_regs[CSSELR_EL1]      = read_sysreg(csselr_el1);
        ctxt->sys_regs[SCTLR_EL1]       = read_sysreg_el1(sctlr);
        ctxt->sys_regs[ACTLR_EL1]       = read_sysreg(actlr_el1);

diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
index 4d55f98f97f78a0b334ec6a585e0d0c3f2915f3a..3dd240ea9e76ec167298e3ae0ad20599d6bb0149 100644 (file)
--- a/virt/kvm/arm/arm.c
+++ b/virt/kvm/arm/arm.c
@@ -1561,6 +1561,7 @@ static int init_hyp_mode(void)
                kvm_cpu_context_t *cpu_ctxt;
 
                cpu_ctxt = per_cpu_ptr(&kvm_host_cpu_state, cpu);
+               kvm_init_host_cpu_context(cpu_ctxt, cpu);
                err = create_hyp_mappings(cpu_ctxt, cpu_ctxt + 1, PAGE_HYP);
 
                if (err) {