[RFC PATCH 3/8] KVM: arm64: Optimise FPSIMD handling to reduce guest/host thrashing
Christoffer Dall
christoffer.dall at arm.com
Thu Apr 26 07:38:02 PDT 2018
On Thu, Apr 26, 2018 at 03:11:49PM +0100, Dave Martin wrote:
> On Thu, Apr 26, 2018 at 01:21:22PM +0200, Christoffer Dall wrote:
> > On Fri, Apr 20, 2018 at 05:46:37PM +0100, Dave Martin wrote:
> > > This patch refactors KVM to align the host and guest FPSIMD
> > > save/restore logic with each other for arm64. This reduces the
> > > number of redundant save/restore operations that must occur, and
> > > reduces the common-case IRQ blackout time during guest exit storms
> > > by saving the host state lazily and optimising away the need to
> > > restore the host state before returning to the run loop.
> > >
> > > Four hooks are defined in order to enable this:
> > >
> > > * kvm_arch_vcpu_run_map_fp():
> > > Called on PID change to map necessary bits of current to Hyp.
> > >
> > > * kvm_arch_vcpu_load_fp():
> > > Set up FP/SIMD for entering the KVM run loop (parse as
> > > "vcpu_load fp").
> > >
> > > * kvm_arch_vcpu_park_fp():
> > > Get FP/SIMD into a safe state for re-enabling interrupts after a
> > > guest exit back to the run loop.
> > >
> > > For arm64 specifically, this involves updating the host kernel's
> > > FPSIMD context tracking metadata so that kernel-mode NEON use
> > > will cause the vcpu's FPSIMD state to be saved back correctly
> > > into the vcpu struct. This must be done before re-enabling
> > > interrupts because kernel-mode NEON may be used my softirqs.
> > >
> > > * kvm_arch_vcpu_put_fp():
> > > Save guest FP/SIMD state back to memory and dissociate from the
> > > CPU ("vcpu_put fp").
> > >
> > > Also, the arm64 FPSIMD context switch code is updated to enable it
> > > to save back FPSIMD state for a vcpu, not just current. A few
> > > helpers drive this:
> > >
> > > * fpsimd_bind_state_to_cpu(struct user_fpsimd_state *fp):
> > > mark this CPU as having context fp (which may belong to a vcpu)
> > > currently loaded in its registers. This is the non-task
> > > equivalent of the static function fpsimd_bind_to_cpu() in
> > > fpsimd.c.
> > >
> > > * task_fpsimd_save():
> > > exported to allow KVM to save the guest's FPSIMD state back to
> > > memory on exit from the run loop.
> > >
> > > * fpsimd_flush_state():
> > > invalidate any context's FPSIMD state that is currently loaded.
> > > Used to disassociate the vcpu from the CPU regs on run loop exit.
> > >
> > > These changes allow the run loop to enable interrupts (and thus
> > > softirqs that may use kernel-mode NEON) without having to save the
> > > guest's FPSIMD state eagerly.
> > >
> > > Some new vcpu_arch fields are added to make all this work. Because
> > > host FPSIMD state can now be saved back directly into current's
> > > thread_struct as appropriate, host_cpu_context is no longer used
> > > for preserving the FPSIMD state. However, it is still needed for
> > > preserving other things such as the host's system registers. To
> > > avoid ABI churn, the redundant storage space in host_cpu_context is
> > > not removed for now.
> > >
> > > arch/arm is not addressed by this patch and continues to use its
> > > current save/restore logic. It could provide implementations of
> > > the helpers later if desired.
> > >
> > > Signed-off-by: Dave Martin <Dave.Martin at arm.com>
> > >
> > > ---
> > >
> > > Changes since RFC v3:
> > >
> > > Requested by Christoffer Dall:
> > >
> > > * Remove fpsimd_flush_state(), which nothing uses.
> > > Inline it back into fpsimd_flush_task_state().
> > >
> > > * Add __hyp_text anootation to update_fp_enabled().
> > >
> > > Other:
> > >
> > > * Remove fp_enabled().
> > >
> > > Now that we have an explicit field vcpu->arch.fp_enabled to
> > > indicate whether the guest's FPSIMD state is loaded, we can use
> > > this to determine when to save FPEXC_EL1 for 32-bit guests.
> > > This brings the logic for FPEXC_EL1 save back into line with the
> > > (updated) logic for restore of this register, and simplifies the
> > > code a bit.
> > >
> > > Signed-off-by: Dave Martin <Dave.Martin at arm.com>
> > > ---
> > > arch/arm/include/asm/kvm_host.h | 8 +++
> > > arch/arm64/include/asm/fpsimd.h | 5 ++
> > > arch/arm64/include/asm/kvm_host.h | 18 +++++++
> > > arch/arm64/kernel/fpsimd.c | 24 ++++++---
> > > arch/arm64/kvm/Makefile | 2 +-
> > > arch/arm64/kvm/fpsimd.c | 109 ++++++++++++++++++++++++++++++++++++++
> > > arch/arm64/kvm/hyp/switch.c | 50 +++++++++--------
> > > virt/kvm/arm/arm.c | 14 ++---
> > > 8 files changed, 187 insertions(+), 43 deletions(-)
> > > create mode 100644 arch/arm64/kvm/fpsimd.c
> > >
> > > diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> > > index c6a7495..3fe01c7 100644
> > > --- a/arch/arm/include/asm/kvm_host.h
> > > +++ b/arch/arm/include/asm/kvm_host.h
> > > @@ -300,6 +300,14 @@ int kvm_arm_vcpu_arch_get_attr(struct kvm_vcpu *vcpu,
> > > int kvm_arm_vcpu_arch_has_attr(struct kvm_vcpu *vcpu,
> > > struct kvm_device_attr *attr);
> > >
> > > +/*
> > > + * VFP/NEON switching is all done by the hyp switch code, so no need to
> > > + * coordinate with host context handling for this state:
> > > + */
> > > +static inline void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) {}
> > > +static inline void kvm_arch_vcpu_park_fp(struct kvm_vcpu *vcpu) {}
> > > +static inline void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) {}
> > > +
> > > /* All host FP/SIMD state is restored on guest exit, so nothing to save: */
> > > static inline void kvm_fpsimd_flush_cpu_state(void) {}
> > >
> > > diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
> > > index aa7162a..a1c5127 100644
> > > --- a/arch/arm64/include/asm/fpsimd.h
> > > +++ b/arch/arm64/include/asm/fpsimd.h
> > > @@ -41,6 +41,8 @@ struct task_struct;
> > > extern void fpsimd_save_state(struct user_fpsimd_state *state);
> > > extern void fpsimd_load_state(struct user_fpsimd_state *state);
> > >
> > > +extern void task_fpsimd_save(void);
> > > +
> > > extern void fpsimd_thread_switch(struct task_struct *next);
> > > extern void fpsimd_flush_thread(void);
> > >
> > > @@ -49,7 +51,10 @@ extern void fpsimd_preserve_current_state(void);
> > > extern void fpsimd_restore_current_state(void);
> > > extern void fpsimd_update_current_state(struct user_fpsimd_state const *state);
> > >
> > > +extern void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *state);
> > > +
> > > extern void fpsimd_flush_task_state(struct task_struct *target);
> > > +extern void fpsimd_flush_cpu_state(void);
> > > extern void sve_flush_cpu_state(void);
> > >
> > > /* Maximum VL that SVE VL-agnostic software can transparently support */
> > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> > > index ab46bc7..2fbfbda 100644
> > > --- 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/thread_info.h>
> > >
> > > #define __KVM_HAVE_ARCH_INTC_INITIALIZED
> > >
> > > @@ -235,6 +236,12 @@ struct kvm_vcpu_arch {
> > >
> > > /* Pointer to host CPU context */
> > > kvm_cpu_context_t *host_cpu_context;
> > > +
> > > + struct thread_info *host_thread_info; /* hyp VA */
> > > + struct user_fpsimd_state *host_fpsimd_state; /* hyp VA */
> > > + bool host_sve_in_use; /* backup for host TIF_SVE while in guest */
> > > + bool fp_enabled;
> > > +
> > > struct {
> > > /* {Break,watch}point registers */
> > > struct kvm_guest_debug_arch regs;
> > > @@ -417,6 +424,17 @@ static inline void __cpu_init_stage2(void)
> > > "PARange is %d bits, unsupported configuration!", parange);
> > > }
> > >
> > > +/* Guest/host FPSIMD coordination helpers */
> > > +int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu);
> > > +void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu);
> > > +void kvm_arch_vcpu_park_fp(struct kvm_vcpu *vcpu);
> > > +void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu);
> > > +
> > > +static inline int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
> > > +{
> > > + return kvm_arch_vcpu_run_map_fp(vcpu);
> > > +}
> > > +
> >
> > nit: It would be nicer to only add the arm64 hook the way they should be
> > in this patch, and remove the #ifdef CONFIG_ARM64 thing that gets
> > removed in this patch from patch 1.
>
> Can do. For now, I was keeping it clear what you write and what I
> changed, but if you're happy with the changes I can fold them together
> and add by S-o-B on top of yours.
>
Yes, I'm happy for you to change the patch in whichever way you find
reasonable for it to fit nicely in this series. I'll promise to read it
carefully as the series go by.
> >
> > > /*
> > > * All host FP/SIMD state is restored on guest exit, so nothing needs
> > > * doing here except in the SVE case:
> > > diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
> > > index 87a3536..7f74374 100644
> > > --- a/arch/arm64/kernel/fpsimd.c
> > > +++ b/arch/arm64/kernel/fpsimd.c
> > > @@ -270,13 +270,15 @@ static void task_fpsimd_load(void)
> > > }
> > >
> > > /*
> > > - * Ensure current's FPSIMD/SVE storage in thread_struct is up to date
> > > + * Ensure current's FPSIMD/SVE storage in memory is up to date
> > > * with respect to the CPU registers.
> > > *
> > > * Softirqs (and preemption) must be disabled.
> > > */
> > > -static void task_fpsimd_save(void)
> > > +void task_fpsimd_save(void)
> > > {
> > > + struct user_fpsimd_state *st = __this_cpu_read(fpsimd_last_state.st);
> > > +
> > > WARN_ON(!in_softirq() && !irqs_disabled());
> > >
> > > if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
> > > @@ -291,10 +293,9 @@ static void task_fpsimd_save(void)
> > > return;
> > > }
> > >
> > > - sve_save_state(sve_pffr(current),
> > > - ¤t->thread.uw.fpsimd_state.fpsr);
> > > + sve_save_state(sve_pffr(current), &st->fpsr);
> > > } else
> > > - fpsimd_save_state(¤t->thread.uw.fpsimd_state);
> > > + fpsimd_save_state(st);
> >
> > Is this equivalent to what we had before, because we'll have run
> > something that sets this cpu's fpsimd_last_state to current's
> > user_fpsimd_state, when scheduling this thread?
>
> It should be, yes -- at least outside the KVM run loop where
> fpsimd_last_state can point into the vcpu instead.
>
> fpsimd_bind_to_cpu() does the setting of fpsimd_last_state. This is
> called when loading current's FPSIMD regs via
> fpsimd_restore_current_state(), or just after exiting the guest if
> vcpu->arch.fp_enabled became set.
>
I see, that makes sense, thanks.
> >
> > > }
> > > }
> > >
> > > @@ -1012,6 +1013,17 @@ static void fpsimd_bind_to_cpu(void)
> > > current->thread.fpsimd_cpu = smp_processor_id();
> > > }
> > >
> > > +void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *st)
> > > +{
> > > + struct fpsimd_last_state_struct *last =
> > > + this_cpu_ptr(&fpsimd_last_state);
> > > +
> > > + WARN_ON(!in_softirq() && !irqs_disabled());
> > > +
> > > + last->st = st;
> > > + last->sve_in_use = false;
> > > +}
> > > +
> > > /*
> > > * Load the userland FPSIMD state of 'current' from memory, but only if the
> > > * FPSIMD state already held in the registers is /not/ the most recent FPSIMD
> > > @@ -1064,7 +1076,7 @@ void fpsimd_flush_task_state(struct task_struct *t)
> > > t->thread.fpsimd_cpu = NR_CPUS;
> > > }
> > >
> > > -static inline void fpsimd_flush_cpu_state(void)
> > > +void fpsimd_flush_cpu_state(void)
> > > {
> > > __this_cpu_write(fpsimd_last_state.st, NULL);
> > > }
> >
> > You could consider factoring out all changes to kernel/fpsimd.c into a
> > separate patch explaining why it's correct, which may make bisecting
> > potential bugs easier, but on the other hand it keeps the changes in the
> > patch where they're used. Just a thought.
>
> I'll have a think about that when I respin. I think the fpsimd.c-only
> part of the patch would be self-evidently correct, so it could make
> sense to keep it separate.
>
>
> >
> > > diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
> > > index 93afff9..0f2a135 100644
> > > --- a/arch/arm64/kvm/Makefile
> > > +++ b/arch/arm64/kvm/Makefile
> > > @@ -19,7 +19,7 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/psci.o $(KVM)/arm/perf.o
> > > kvm-$(CONFIG_KVM_ARM_HOST) += inject_fault.o regmap.o va_layout.o
> > > kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o
> > > kvm-$(CONFIG_KVM_ARM_HOST) += guest.o debug.o reset.o sys_regs.o sys_regs_generic_v8.o
> > > -kvm-$(CONFIG_KVM_ARM_HOST) += vgic-sys-reg-v3.o
> > > +kvm-$(CONFIG_KVM_ARM_HOST) += vgic-sys-reg-v3.o fpsimd.o
> > > kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/aarch32.o
> > >
> > > kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic.o
> > > diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
> > > new file mode 100644
> > > index 0000000..cc7a068
> > > --- /dev/null
> > > +++ b/arch/arm64/kvm/fpsimd.c
> > > @@ -0,0 +1,109 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > > + * arch/arm64/kvm/fpsimd.c: Guest/host FPSIMD context coordination helpers
> > > + *
> > > + * Copyright 2018 Arm Limited
> > > + * Author: Dave Martin <Dave.Martin at arm.com>
> > > + */
> > > +#include <linux/bottom_half.h>
> > > +#include <linux/sched.h>
> > > +#include <linux/thread_info.h>
> > > +#include <linux/kvm_host.h>
> > > +#include <asm/kvm_host.h>
> > > +#include <asm/kvm_mmu.h>
> > > +
> > > +/*
> > > + * Called on entry to KVM_RUN unless this vcpu previously ran at least
> > > + * once and the most recent prior KVM_RUN for this vcpu was called from
> > > + * the same task as current (highly likely).
> > > + *
> > > + * This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu),
> > > + * such that on entering hyp the relevant parts of current are already
> > > + * mapped.
> > > + */
> > > +int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
> > > +{
> > > + int ret;
> > > +
> > > + struct thread_info *ti = ¤t->thread_info;
> > > + struct user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state;
> > > +
> > > + /*
> > > + * Make sure the host task thread flags and fpsimd state are
> > > + * visible to hyp:
> > > + */
> > > + ret = create_hyp_mappings(ti, ti + 1, PAGE_HYP);
> > > + if (ret)
> > > + goto error;
> > > +
> > > + ret = create_hyp_mappings(fpsimd, fpsimd + 1, PAGE_HYP);
> > > + if (ret)
> > > + goto error;
> > > +
> > > + vcpu->arch.host_thread_info = kern_hyp_va(ti);
> > > + vcpu->arch.host_fpsimd_state = kern_hyp_va(fpsimd);
> > > +error:
> > > + return ret;
> > > +}
> > > +
> > > +/*
> > > + * Prepare vcpu for saving the host's FPSIMD state and loading the guest's.
> > > + * The actual loading is done by the FPSIMD access trap taken to hyp.
> > > + *
> > > + * Here, we just set the correct metadata to indicate that the FPSIMD
> > > + * state in the cpu regs (if any) belongs to current, and where to write
> > > + * it back to if/when a FPSIMD access trap is taken.
> > > + *
> > > + * TIF_SVE is backed up here, since it may get clobbered with guest state.
> > > + * This flag is restored by kvm_arch_vcpu_put_fp(vcpu).
> >
> > I don't fully understand how TIF_SVE gets clobbered, but perhaps that's
> > in preparation for a future patch. (Me keeps reading).
>
> task_fpsimd_save() relies on that flag to tell it whether to save SVE
> or FPSIMD state. For now, we must not attempt to save SVE state for a
> vcpu, since we have nowhere to store it, so TIF_SVE is cleared
> explicitly in _park_fp() is vcpu->arch.fp_enabled got set while in the
> guest (i.e., the guest's FPSIMD state got loaded).
I missed that during my initial look. Sorry.
>
> In the future it may get set or not, depending on whether the guest is
> using SVE.
>
> Do you think the comment is adequate? Perhaps I can reword it.
>
I think it's fine, I should just pay closer attention.
> > > + */
> > > +void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
> > > +{
> > > + BUG_ON(system_supports_sve());
> > > + BUG_ON(!current->mm);
> > > +
> > > + vcpu->arch.fp_enabled = false;
> > > + vcpu->arch.host_fpsimd_state =
> > > + kern_hyp_va(¤t->thread.uw.fpsimd_state);
> > > + vcpu->arch.host_sve_in_use = !!test_thread_flag(TIF_SVE);
> > > +}
> > > +
> > > +/*
> > > + * If the guest FPSIMD state was loaded, mark the CPU FPSIMD regs as
> > > + * dirty for vcpu so that they will be written back if the kernel
> > > + * clobbers them due to kernel-mode NEON before re-entry into the guest.
> > > + */
> > > +void kvm_arch_vcpu_park_fp(struct kvm_vcpu *vcpu)
> > > +{
> > > + WARN_ON_ONCE(!irqs_disabled());
> > > +
> > > + if (vcpu->arch.fp_enabled) {
> > > + fpsimd_bind_state_to_cpu(&vcpu->arch.ctxt.gp_regs.fp_regs);
> > > + clear_thread_flag(TIF_FOREIGN_FPSTATE);
> > > + clear_thread_flag(TIF_SVE);
> > > + }
> > > +}
> > > +
> > > +/*
> > > + * Write back the vcpu FPSIMD regs if they are dirty, and invalidate the
> > > + * cpu FPSIMD regs so that they can't be spuriously reused if this vcpu
> > > + * disappears and another task or vcpu appears that recycles the same
> > > + * struct fpsimd_state.
> > > + */
> > > +void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
> > > +{
> > > + local_bh_disable();
> > > +
> > > + if (vcpu->arch.fp_enabled) {
> > > + task_fpsimd_save();
> >
> > Just to make sure I'm getting this right: This is safe, because even if
> > after we exited the VM, before we call this function, if we take a
> > softirq that has overwritten our fpsimd state, then kernel_neon_begin()
> > will have set TIF_FOREIGN_FPSTATE, and task_fpsimd_save() won't actually
> > do anything, and kernel_neon_begin() will have alreay saved the VCPU's
> > fpsimd state. Is that right?
>
> Exactly. The local_bh_disable() here is crucial to make sure that
> kernel-mode NEON can't tread on our toes while we do the dirty work.
>
> > > + fpsimd_flush_cpu_state();
> > > + set_thread_flag(TIF_FOREIGN_FPSTATE);
> > > + }
> > > +
> > > + if (vcpu->arch.host_sve_in_use)
> > > + set_thread_flag(TIF_SVE);
> > > + else
> > > + clear_thread_flag(TIF_SVE);
> > > +
> > > + local_bh_enable();
> > > +}
> > > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> > > index c438ad8..0900c2a 100644
> > > --- a/arch/arm64/kvm/hyp/switch.c
> > > +++ b/arch/arm64/kvm/hyp/switch.c
> > > @@ -27,15 +27,16 @@
> > > #include <asm/kvm_mmu.h>
> > > #include <asm/fpsimd.h>
> > > #include <asm/debug-monitors.h>
> > > +#include <asm/thread_info.h>
> > >
> > > -static bool __hyp_text __fpsimd_enabled_nvhe(void)
> > > +static bool __hyp_text update_fp_enabled(struct kvm_vcpu *vcpu)
> > > {
> > > - return !(read_sysreg(cptr_el2) & CPTR_EL2_TFP);
> > > -}
> > > + if (vcpu->arch.host_thread_info->flags & _TIF_FOREIGN_FPSTATE) {
> > > + vcpu->arch.host_fpsimd_state = NULL;
> > > + vcpu->arch.fp_enabled = false;
> > > + }
> > >
> > > -static bool fpsimd_enabled_vhe(void)
> > > -{
> > > - return !!(read_sysreg(cpacr_el1) & CPACR_EL1_FPEN);
> > > + return vcpu->arch.fp_enabled;
> > > }
> > >
> > > /* Save the 32-bit only FPSIMD system register state */
> > > @@ -92,7 +93,10 @@ static void activate_traps_vhe(struct kvm_vcpu *vcpu)
> > >
> > > val = read_sysreg(cpacr_el1);
> > > val |= CPACR_EL1_TTA;
> > > - val &= ~(CPACR_EL1_FPEN | CPACR_EL1_ZEN);
> > > + val &= ~CPACR_EL1_ZEN;
> > > + if (!update_fp_enabled(vcpu))
> > > + val &= ~CPACR_EL1_FPEN;
> > > +
> > > write_sysreg(val, cpacr_el1);
> > >
> > > write_sysreg(kvm_get_hyp_vector(), vbar_el1);
> > > @@ -105,7 +109,10 @@ static void __hyp_text __activate_traps_nvhe(struct kvm_vcpu *vcpu)
> > > __activate_traps_common(vcpu);
> > >
> > > val = CPTR_EL2_DEFAULT;
> > > - val |= CPTR_EL2_TTA | CPTR_EL2_TFP | CPTR_EL2_TZ;
> > > + val |= CPTR_EL2_TTA | CPTR_EL2_TZ;
> > > + if (!update_fp_enabled(vcpu))
> > > + val |= CPTR_EL2_TFP;
> > > +
> > > write_sysreg(val, cptr_el2);
> > > }
> > >
> > > @@ -394,7 +401,6 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
> > > {
> > > struct kvm_cpu_context *host_ctxt;
> > > struct kvm_cpu_context *guest_ctxt;
> > > - bool fp_enabled;
> > > u64 exit_code;
> > >
> > > host_ctxt = vcpu->arch.host_cpu_context;
> > > @@ -416,19 +422,14 @@ int kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)
> > > /* And we're baaack! */
> > > } while (fixup_guest_exit(vcpu, &exit_code));
> > >
> > > - fp_enabled = fpsimd_enabled_vhe();
> > > -
> > > sysreg_save_guest_state_vhe(guest_ctxt);
> > >
> > > __deactivate_traps(vcpu);
> > >
> > > sysreg_restore_host_state_vhe(host_ctxt);
> > >
> > > - if (fp_enabled) {
> > > - __fpsimd_save_state(&guest_ctxt->gp_regs.fp_regs);
> > > - __fpsimd_restore_state(&host_ctxt->gp_regs.fp_regs);
> > > + if (vcpu->arch.fp_enabled)
> > > __fpsimd_save_fpexc32(vcpu);
> > > - }
> > >
> > > __debug_switch_to_host(vcpu);
> > >
> > > @@ -440,7 +441,6 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
> > > {
> > > struct kvm_cpu_context *host_ctxt;
> > > struct kvm_cpu_context *guest_ctxt;
> > > - bool fp_enabled;
> > > u64 exit_code;
> > >
> > > vcpu = kern_hyp_va(vcpu);
> > > @@ -472,8 +472,6 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
> > > /* And we're baaack! */
> > > } while (fixup_guest_exit(vcpu, &exit_code));
> > >
> > > - fp_enabled = __fpsimd_enabled_nvhe();
> > > -
> > > __sysreg_save_state_nvhe(guest_ctxt);
> > > __sysreg32_save_state(vcpu);
> > > __timer_disable_traps(vcpu);
> > > @@ -484,11 +482,8 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
> > >
> > > __sysreg_restore_state_nvhe(host_ctxt);
> > >
> > > - if (fp_enabled) {
> > > - __fpsimd_save_state(&guest_ctxt->gp_regs.fp_regs);
> > > - __fpsimd_restore_state(&host_ctxt->gp_regs.fp_regs);
> > > + if (vcpu->arch.fp_enabled)
> > > __fpsimd_save_fpexc32(vcpu);
> > > - }
> > >
> > > /*
> > > * This must come after restoring the host sysregs, since a non-VHE
> > > @@ -502,8 +497,6 @@ int __hyp_text __kvm_vcpu_run_nvhe(struct kvm_vcpu *vcpu)
> > > void __hyp_text __hyp_switch_fpsimd(u64 esr __always_unused,
> > > struct kvm_vcpu *vcpu)
> > > {
> > > - kvm_cpu_context_t *host_ctxt;
> > > -
> > > if (has_vhe())
> > > write_sysreg(read_sysreg(cpacr_el1) | CPACR_EL1_FPEN,
> > > cpacr_el1);
> > > @@ -513,14 +506,19 @@ void __hyp_text __hyp_switch_fpsimd(u64 esr __always_unused,
> > >
> > > isb();
> > >
> > > - host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
> > > - __fpsimd_save_state(&host_ctxt->gp_regs.fp_regs);
> > > + if (vcpu->arch.host_fpsimd_state) {
> > > + __fpsimd_save_state(vcpu->arch.host_fpsimd_state);
> > > + vcpu->arch.host_fpsimd_state = NULL;
> > > + }
> > > +
> > > __fpsimd_restore_state(&vcpu->arch.ctxt.gp_regs.fp_regs);
> > >
> > > /* Skip restoring fpexc32 for AArch64 guests */
> > > if (!(read_sysreg(hcr_el2) & HCR_RW))
> > > write_sysreg(vcpu->arch.ctxt.sys_regs[FPEXC32_EL2],
> > > fpexc32_el2);
> > > +
> > > + vcpu->arch.fp_enabled = true;
> > > }
> > >
> > > static const char __hyp_panic_string[] = "HYP panic:\nPS:%08llx PC:%016llx ESR:%08llx\nFAR:%016llx HPFAR:%016llx PAR:%016llx\nVCPU:%p\n";
> > > diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> > > index cd38d7d..4fcf6fe 100644
> > > --- a/virt/kvm/arm/arm.c
> > > +++ b/virt/kvm/arm/arm.c
> > > @@ -363,10 +363,12 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> > > kvm_vgic_load(vcpu);
> > > kvm_timer_vcpu_load(vcpu);
> > > kvm_vcpu_load_sysregs(vcpu);
> > > + kvm_arch_vcpu_load_fp(vcpu);
> > > }
> > >
> > > void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> > > {
> > > + kvm_arch_vcpu_put_fp(vcpu);
> > > kvm_vcpu_put_sysregs(vcpu);
> > > kvm_timer_vcpu_put(vcpu);
> > > kvm_vgic_put(vcpu);
> > > @@ -773,6 +775,8 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
> > > if (static_branch_unlikely(&userspace_irqchip_in_use))
> > > kvm_timer_sync_hwstate(vcpu);
> > >
> > > + kvm_arch_vcpu_park_fp(vcpu);
> > > +
> > > /*
> > > * We may have taken a host interrupt in HYP mode (ie
> > > * while executing the guest). This interrupt is still
> > > @@ -816,16 +820,6 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
> > > return ret;
> > > }
> > >
> > > -#ifdef CONFIG_ARM64
> > > -int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu)
> > > -{
> > > - struct task_struct *tsk = current;
> > > -
> > > - /* Make sure the host task fpsimd state is visible to hyp: */
> > > - return create_hyp_mappings(tsk, tsk + 1, PAGE_HYP);
> > > -}
> > > -#endif
> > > -
> > > static int vcpu_interrupt_line(struct kvm_vcpu *vcpu, int number, bool level)
> > > {
> > > int bit_index;
> > > --
> > > 2.1.4
> > >
> > Besides the cosmetic comments and questions above, this all looks good
> > to me!
>
> Thanks for the review.
>
> I wanted to do a respin to clean up the series anyhow, so I'll try to
> address your comments there:
>
Thanks,
-Christoffer
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