mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-08-05 16:54:27 +00:00
42ce432522
Historically KVM hyp code saved the host's FPSIMD state into the hosts's fpsimd_state memory, and so it was necessary to map this into the hyp Stage-1 mappings before running a vCPU. This is no longer necessary as of commits: *fbc7e61195("KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state") *8eca7f6d51("KVM: arm64: Remove host FPSIMD saving for non-protected KVM") Since those commits, we eagerly save the host's FPSIMD state before calling into hyp to run a vCPU, and hyp code never reads nor writes the host's fpsimd_state memory. There's no longer any need to map the host's fpsimd_state memory into the hyp Stage-1, and kvm_arch_vcpu_run_map_fp() is unnecessary but benign. Remove kvm_arch_vcpu_run_map_fp(). Currently there is no code to perform a corresponding unmap, and we never mapped the host's SVE or SME state into the hyp Stage-1, so no other code needs to be removed. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Fuad Tabba <tabba@google.com> Cc: Marc Zyngier <maz@kernel.org> Cc: Mark Brown <broonie@kernel.org> Cc: Oliver Upton <oliver.upton@linux.dev> Cc: Will Deacon <will@kernel.org> Cc: kvmarm@lists.linux.dev Reviewed-by: Mark Brown <broonie@kernel.org> Tested-by: Fuad Tabba <tabba@google.com> Reviewed-by: Fuad Tabba <tabba@google.com> Link: https://lore.kernel.org/r/20250619134817.4075340-1-mark.rutland@arm.com Signed-off-by: Marc Zyngier <maz@kernel.org>
122 lines
3.7 KiB
C
122 lines
3.7 KiB
C
// 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@arm.com>
|
|
*/
|
|
#include <linux/irqflags.h>
|
|
#include <linux/sched.h>
|
|
#include <linux/kvm_host.h>
|
|
#include <asm/fpsimd.h>
|
|
#include <asm/kvm_asm.h>
|
|
#include <asm/kvm_hyp.h>
|
|
#include <asm/kvm_mmu.h>
|
|
#include <asm/sysreg.h>
|
|
|
|
/*
|
|
* 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 on the host.
|
|
*/
|
|
void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
|
|
{
|
|
BUG_ON(!current->mm);
|
|
|
|
if (!system_supports_fpsimd())
|
|
return;
|
|
|
|
/*
|
|
* Ensure that any host FPSIMD/SVE/SME state is saved and unbound such
|
|
* that the host kernel is responsible for restoring this state upon
|
|
* return to userspace, and the hyp code doesn't need to save anything.
|
|
*
|
|
* When the host may use SME, fpsimd_save_and_flush_cpu_state() ensures
|
|
* that PSTATE.{SM,ZA} == {0,0}.
|
|
*/
|
|
fpsimd_save_and_flush_cpu_state();
|
|
*host_data_ptr(fp_owner) = FP_STATE_FREE;
|
|
|
|
WARN_ON_ONCE(system_supports_sme() && read_sysreg_s(SYS_SVCR));
|
|
}
|
|
|
|
/*
|
|
* Called just before entering the guest once we are no longer preemptible
|
|
* and interrupts are disabled. If we have managed to run anything using
|
|
* FP while we were preemptible (such as off the back of an interrupt),
|
|
* then neither the host nor the guest own the FP hardware (and it was the
|
|
* responsibility of the code that used FP to save the existing state).
|
|
*/
|
|
void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
|
|
{
|
|
if (test_thread_flag(TIF_FOREIGN_FPSTATE))
|
|
*host_data_ptr(fp_owner) = FP_STATE_FREE;
|
|
}
|
|
|
|
/*
|
|
* Called just after exiting the guest. If the guest FPSIMD state
|
|
* was loaded, update the host's context tracking data mark the CPU
|
|
* FPSIMD regs as dirty and belonging to 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_ctxsync_fp(struct kvm_vcpu *vcpu)
|
|
{
|
|
struct cpu_fp_state fp_state;
|
|
|
|
WARN_ON_ONCE(!irqs_disabled());
|
|
|
|
if (guest_owns_fp_regs()) {
|
|
/*
|
|
* Currently we do not support SME guests so SVCR is
|
|
* always 0 and we just need a variable to point to.
|
|
*/
|
|
fp_state.st = &vcpu->arch.ctxt.fp_regs;
|
|
fp_state.sve_state = vcpu->arch.sve_state;
|
|
fp_state.sve_vl = vcpu->arch.sve_max_vl;
|
|
fp_state.sme_state = NULL;
|
|
fp_state.svcr = __ctxt_sys_reg(&vcpu->arch.ctxt, SVCR);
|
|
fp_state.fpmr = __ctxt_sys_reg(&vcpu->arch.ctxt, FPMR);
|
|
fp_state.fp_type = &vcpu->arch.fp_type;
|
|
|
|
if (vcpu_has_sve(vcpu))
|
|
fp_state.to_save = FP_STATE_SVE;
|
|
else
|
|
fp_state.to_save = FP_STATE_FPSIMD;
|
|
|
|
fpsimd_bind_state_to_cpu(&fp_state);
|
|
|
|
clear_thread_flag(TIF_FOREIGN_FPSTATE);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
unsigned long flags;
|
|
|
|
local_irq_save(flags);
|
|
|
|
if (guest_owns_fp_regs()) {
|
|
/*
|
|
* Flush (save and invalidate) the fpsimd/sve state so that if
|
|
* the host tries to use fpsimd/sve, it's not using stale data
|
|
* from the guest.
|
|
*
|
|
* Flushing the state sets the TIF_FOREIGN_FPSTATE bit for the
|
|
* context unconditionally, in both nVHE and VHE. This allows
|
|
* the kernel to restore the fpsimd/sve state, including ZCR_EL1
|
|
* when needed.
|
|
*/
|
|
fpsimd_save_and_flush_cpu_state();
|
|
}
|
|
|
|
local_irq_restore(flags);
|
|
}
|