Hi Christoffer,

On 01/12/2018 12:07 PM, Christoffer Dall wrote:
Avoid saving the guest VFP registers and restoring the host VFP
registers on every exit from the VM.  Only when we're about to run
userspace or other threads in the kernel do we really have to switch the


s/do// ?

state back to the host state.

We still initially configure the VFP registers to trap when entering the
VM, but the difference is that we now leave the guest state in the
hardware registers as long as we're running this VCPU, even if we
occasionally trap to the host, and we only restore the host state when
we return to user space or when scheduling another thread.

Reviewed-by: Andrew Jones <drjo...@redhat.com>
Reviewed-by: Marc Zyngier <marc.zyng...@arm.com>
Signed-off-by: Christoffer Dall <christoffer.d...@linaro.org>
---
  arch/arm64/include/asm/kvm_host.h |  3 +++
  arch/arm64/kernel/asm-offsets.c   |  1 +
  arch/arm64/kvm/hyp/entry.S        |  3 +++
  arch/arm64/kvm/hyp/switch.c       | 48 ++++++++++++---------------------------
  arch/arm64/kvm/hyp/sysreg-sr.c    | 21 ++++++++++++++---
  5 files changed, 40 insertions(+), 36 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h 
b/arch/arm64/include/asm/kvm_host.h
index 0e9e7291a7e6..9e23bc968668 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -213,6 +213,9 @@ struct kvm_vcpu_arch {
        /* Guest debug state */
        u64 debug_flags;
+ /* 1 if the guest VFP state is loaded into the hardware */
+       u8 guest_vfp_loaded;
+
        /*
         * We maintain more than a single set of debug registers to support
         * debugging the guest from the host and to maintain separate host and
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index 612021dce84f..99467327c043 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -133,6 +133,7 @@ int main(void)
    DEFINE(CPU_GP_REGS,         offsetof(struct kvm_cpu_context, gp_regs));
    DEFINE(CPU_USER_PT_REGS,    offsetof(struct kvm_regs, regs));
    DEFINE(CPU_FP_REGS,         offsetof(struct kvm_regs, fp_regs));
+  DEFINE(VCPU_GUEST_VFP_LOADED,        offsetof(struct kvm_vcpu, 
arch.guest_vfp_loaded));
    DEFINE(VCPU_FPEXC32_EL2,    offsetof(struct kvm_vcpu, 
arch.ctxt.sys_regs[FPEXC32_EL2]));
    DEFINE(VCPU_HOST_CONTEXT,   offsetof(struct kvm_vcpu, 
arch.host_cpu_context));
    DEFINE(HOST_CONTEXT_VCPU,   offsetof(struct kvm_cpu_context, 
__hyp_running_vcpu));
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index a360ac6e89e9..53652287a236 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -184,6 +184,9 @@ alternative_endif
        add     x0, x2, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
        bl      __fpsimd_restore_state
+ mov x0, #1
+       strb    w0, [x3, #VCPU_GUEST_VFP_LOADED]
+
        // Skip restoring fpexc32 for AArch64 guests
        mrs     x1, hcr_el2
        tbnz    x1, #HCR_RW_SHIFT, 1f
diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
index 12dc647a6e5f..29e44a20f5e3 100644
--- a/arch/arm64/kvm/hyp/switch.c
+++ b/arch/arm64/kvm/hyp/switch.c
@@ -24,43 +24,32 @@
  #include <asm/fpsimd.h>
  #include <asm/debug-monitors.h>
-static bool __hyp_text __fpsimd_enabled_nvhe(void)
-{
-       return !(read_sysreg(cptr_el2) & CPTR_EL2_TFP);
-}
-
-static bool __hyp_text __fpsimd_enabled_vhe(void)
-{
-       return !!(read_sysreg(cpacr_el1) & CPACR_EL1_FPEN);
-}
-
-static hyp_alternate_select(__fpsimd_is_enabled,
-                           __fpsimd_enabled_nvhe, __fpsimd_enabled_vhe,
-                           ARM64_HAS_VIRT_HOST_EXTN);
-
-bool __hyp_text __fpsimd_enabled(void)

Now that __fpsimd_enabled is removed, I think you need to remove the prototype in arch/arm64/include/kvm_hyp.h too.

-{
-       return __fpsimd_is_enabled()();
-}

Cheers,

--
Julien Grall
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