[PATCH v2 5/5] KVM: arm64: Exclude FP ownership from kvm_vcpu_arch

Marc Zyngier
2024-03-22T17:10:11Z

In retrospect, it is fairly obvious that the FP state ownership
is only meaningful for a given CPU, and that locating this
information in the vcpu was just a mistake.

Move the ownership tracking into the host data structure, and
rename it from fp_state to fp_owner, which is a better description
(name suggested by Mark Brown).

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm64/include/asm/kvm_emulate.h | 4 ++--
arch/arm64/include/asm/kvm_host.h | 14 +++++++-------
arch/arm64/kvm/arm.c | 6 ------
arch/arm64/kvm/fpsimd.c | 10 +++++-----
arch/arm64/kvm/hyp/include/hyp/switch.h | 6 +++---
arch/arm64/kvm/hyp/nvhe/hyp-main.c | 2 --
arch/arm64/kvm/hyp/nvhe/switch.c | 2 +-
arch/arm64/kvm/hyp/vhe/switch.c | 2 +-
8 files changed, 19 insertions(+), 27 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index debc3753d2ef..b17f2269fb81 100644
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -594,7 +594,7 @@ static __always_inline u64 kvm_get_reset_cptr_el2(struct kvm_vcpu *vcpu)
val = (CPACR_EL1_FPEN_EL0EN | CPACR_EL1_FPEN_EL1EN);

if (!vcpu_has_sve(vcpu) ||
- (vcpu->arch.fp_state != FP_STATE_GUEST_OWNED))
+ (*host_data_ptr(fp_owner) != FP_STATE_GUEST_OWNED))
val |= CPACR_EL1_ZEN_EL1EN | CPACR_EL1_ZEN_EL0EN;
if (cpus_have_final_cap(ARM64_SME))
val |= CPACR_EL1_SMEN_EL1EN | CPACR_EL1_SMEN_EL0EN;
@@ -602,7 +602,7 @@ static __always_inline u64 kvm_get_reset_cptr_el2(struct kvm_vcpu *vcpu)
val = CPTR_NVHE_EL2_RES1;

if (vcpu_has_sve(vcpu) &&
- (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED))
+ (*host_data_ptr(fp_owner) == FP_STATE_GUEST_OWNED))
val |= CPTR_EL2_TZ;
if (cpus_have_final_cap(ARM64_SME))
val &= ~CPTR_EL2_TSM;
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 838cdee2ecf7..951303e976de 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -545,6 +545,13 @@ struct kvm_host_data {
struct kvm_cpu_context host_ctxt;
struct user_fpsimd_state *fpsimd_state; /* hyp VA */

+ /* Ownership of the FP regs */
+ enum {
+ FP_STATE_FREE,
+ FP_STATE_HOST_OWNED,
+ FP_STATE_GUEST_OWNED,
+ } fp_owner;
+
/*
* host_debug_state contains the host registers which are
* saved and restored during world switches.
@@ -621,13 +628,6 @@ struct kvm_vcpu_arch {
/* Exception Information */
struct kvm_vcpu_fault_info fault;

- /* Ownership of the FP regs */
- enum {
- FP_STATE_FREE,
- FP_STATE_HOST_OWNED,
- FP_STATE_GUEST_OWNED,
- } fp_state;
-
/* Configuration flags, set once and for all before the vcpu can run */
u8 cflags;

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index a24287c3ba99..66d8112da268 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -378,12 +378,6 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)

vcpu->arch.mmu_page_cache.gfp_zero = __GFP_ZERO;

- /*
- * Default value for the FP state, will be overloaded at load
- * time if we support FP (pretty likely)
- */
- vcpu->arch.fp_state = FP_STATE_FREE;
-
/* Set up the timer */
kvm_timer_vcpu_init(vcpu);

diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index e6bd99358615..98f8b9272e24 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -84,7 +84,7 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
* guest in kvm_arch_vcpu_ctxflush_fp() and override this to
* FP_STATE_FREE if the flag set.
*/
- vcpu->arch.fp_state = FP_STATE_HOST_OWNED;
+ *host_data_ptr(fp_owner) = FP_STATE_HOST_OWNED;
*host_data_ptr(fpsimd_state) = kern_hyp_va(&current->thread.uw.fpsimd_state);

vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
@@ -109,7 +109,7 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
* been saved, this is very unlikely to happen.
*/
if (read_sysreg_s(SYS_SVCR) & (SVCR_SM_MASK | SVCR_ZA_MASK)) {
- vcpu->arch.fp_state = FP_STATE_FREE;
+ *host_data_ptr(fp_owner) = FP_STATE_FREE;
fpsimd_save_and_flush_cpu_state();
}
}
@@ -125,7 +125,7 @@ void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu)
{
if (test_thread_flag(TIF_FOREIGN_FPSTATE))
- vcpu->arch.fp_state = FP_STATE_FREE;
+ *host_data_ptr(fp_owner) = FP_STATE_FREE;
}

/*
@@ -141,7 +141,7 @@ void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu)

WARN_ON_ONCE(!irqs_disabled());

- if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
+ if (*host_data_ptr(fp_owner) == FP_STATE_GUEST_OWNED) {

/*
* Currently we do not support SME guests so SVCR is
@@ -194,7 +194,7 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
isb();
}

- if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED) {
+ if (*host_data_ptr(fp_owner) == FP_STATE_GUEST_OWNED) {
if (vcpu_has_sve(vcpu)) {
__vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_el1(SYS_ZCR);

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 6def6ad8dd48..2629420d0659 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -42,7 +42,7 @@ extern struct kvm_exception_table_entry __stop___kvm_ex_table;
/* Check whether the FP regs are owned by the guest */
static inline bool guest_owns_fp_regs(struct kvm_vcpu *vcpu)
{
- return vcpu->arch.fp_state == FP_STATE_GUEST_OWNED;
+ return *host_data_ptr(fp_owner) == FP_STATE_GUEST_OWNED;
}

/* Save the 32-bit only FPSIMD system register state */
@@ -376,7 +376,7 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
isb();

/* Write out the host state if it's in the registers */
- if (vcpu->arch.fp_state == FP_STATE_HOST_OWNED)
+ if (*host_data_ptr(fp_owner) == FP_STATE_HOST_OWNED)
__fpsimd_save_state(*host_data_ptr(fpsimd_state));

/* Restore the guest state */
@@ -389,7 +389,7 @@ static bool kvm_hyp_handle_fpsimd(struct kvm_vcpu *vcpu, u64 *exit_code)
if (!(read_sysreg(hcr_el2) & HCR_RW))
write_sysreg(__vcpu_sys_reg(vcpu, FPEXC32_EL2), fpexc32_el2);

- vcpu->arch.fp_state = FP_STATE_GUEST_OWNED;
+ *host_data_ptr(fp_owner) = FP_STATE_GUEST_OWNED;

return true;
}
diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
index c5f625dc1f07..26561c562f7a 100644
--- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
+++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
@@ -39,7 +39,6 @@ static void flush_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu)
hyp_vcpu->vcpu.arch.cptr_el2 = host_vcpu->arch.cptr_el2;

hyp_vcpu->vcpu.arch.iflags = host_vcpu->arch.iflags;
- hyp_vcpu->vcpu.arch.fp_state = host_vcpu->arch.fp_state;

hyp_vcpu->vcpu.arch.debug_ptr = kern_hyp_va(host_vcpu->arch.debug_ptr);

@@ -63,7 +62,6 @@ static void sync_hyp_vcpu(struct pkvm_hyp_vcpu *hyp_vcpu)
host_vcpu->arch.fault = hyp_vcpu->vcpu.arch.fault;

host_vcpu->arch.iflags = hyp_vcpu->vcpu.arch.iflags;
- host_vcpu->arch.fp_state = hyp_vcpu->vcpu.arch.fp_state;

host_cpu_if->vgic_hcr = hyp_cpu_if->vgic_hcr;
for (i = 0; i < hyp_cpu_if->used_lrs; ++i)
diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
index 544a419b9a39..1f82d531a494 100644
--- a/arch/arm64/kvm/hyp/nvhe/switch.c
+++ b/arch/arm64/kvm/hyp/nvhe/switch.c
@@ -337,7 +337,7 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu)

__sysreg_restore_state_nvhe(host_ctxt);

- if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED)
+ if (*host_data_ptr(fp_owner) == FP_STATE_GUEST_OWNED)
__fpsimd_save_fpexc32(vcpu);

__debug_switch_to_host(vcpu);
diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
index 14b7a6bc5909..b92f9fe2d50e 100644
--- a/arch/arm64/kvm/hyp/vhe/switch.c
+++ b/arch/arm64/kvm/hyp/vhe/switch.c
@@ -258,7 +258,7 @@ static int __kvm_vcpu_run_vhe(struct kvm_vcpu *vcpu)

sysreg_restore_host_state_vhe(host_ctxt);

- if (vcpu->arch.fp_state == FP_STATE_GUEST_OWNED)
+ if (*host_data_ptr(fp_owner) == FP_STATE_GUEST_OWNED)
__fpsimd_save_fpexc32(vcpu);

__debug_switch_to_host(vcpu);
--
2.39.2