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

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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>
This commit is contained in:
Marc Zyngier 2019-01-19 15:29:54 +00:00
parent d18232ea8a
commit 32f1395519
5 changed files with 17 additions and 2 deletions
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8
arch/arm/include/asm/kvm_host.h
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@ -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;

1
arch/arm/kvm/hyp/cp15-sr.c
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@ -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);

8
arch/arm64/include/asm/kvm_host.h
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@ -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,

1
arch/arm64/kvm/hyp/sysreg-sr.c
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@ -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);

1
virt/kvm/arm/arm.c
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@ -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) {