[PATCHv2] kvm: arm64: Add SVE support for nVHE.
Daniel Kiss
daniel.kiss at arm.com
Tue Feb 2 13:52:54 EST 2021
CPUs that support SVE are architecturally required to support the
Virtualization Host Extensions (VHE), so far the kernel supported
SVE alongside KVM with VHE enabled. In same cases it is desired to
run nVHE config even when VHE is available.
This patch add support for SVE for nVHE configuration too.
Tested on FVP with a Linux guest VM that run with a different VL than
the host system.
Signed-off-by: Daniel Kiss <daniel.kiss at arm.com>
---
arch/arm64/Kconfig | 7 -----
arch/arm64/include/asm/fpsimd.h | 6 ++++
arch/arm64/include/asm/fpsimdmacros.h | 24 +++++++++++++--
arch/arm64/include/asm/kvm_host.h | 17 +++--------
arch/arm64/kernel/entry-fpsimd.S | 5 ----
arch/arm64/kvm/arm.c | 5 ----
arch/arm64/kvm/fpsimd.c | 39 ++++++++++++++++++++-----
arch/arm64/kvm/hyp/fpsimd.S | 15 ++++++++++
arch/arm64/kvm/hyp/include/hyp/switch.h | 34 +++++++++++----------
arch/arm64/kvm/hyp/nvhe/switch.c | 29 +++++++++++++++++-
arch/arm64/kvm/reset.c | 6 +---
11 files changed, 126 insertions(+), 61 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index f39568b28ec1..049428f1bf27 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1676,7 +1676,6 @@ endmenu
config ARM64_SVE
bool "ARM Scalable Vector Extension support"
default y
- depends on !KVM || ARM64_VHE
help
The Scalable Vector Extension (SVE) is an extension to the AArch64
execution state which complements and extends the SIMD functionality
@@ -1705,12 +1704,6 @@ config ARM64_SVE
booting the kernel. If unsure and you are not observing these
symptoms, you should assume that it is safe to say Y.
- CPUs that support SVE are architecturally required to support the
- Virtualization Host Extensions (VHE), so the kernel makes no
- provision for supporting SVE alongside KVM without VHE enabled.
- Thus, you will need to enable CONFIG_ARM64_VHE if you want to support
- KVM in the same kernel image.
-
config ARM64_MODULE_PLTS
bool "Use PLTs to allow module memory to spill over into vmalloc area"
depends on MODULES
diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index bec5f14b622a..526d69f3eeb3 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -69,6 +69,12 @@ static inline void *sve_pffr(struct thread_struct *thread)
extern void sve_save_state(void *state, u32 *pfpsr);
extern void sve_load_state(void const *state, u32 const *pfpsr,
unsigned long vq_minus_1);
+/*
+ * sve_load_state_nvhe function for the hyp code where the SVE registers are
+ * handled from the EL2, vector length is governed by ZCR_EL2.
+ */
+extern void sve_load_state_nvhe(void const *state, u32 const *pfpsr,
+ unsigned long vq_minus_1);
extern void sve_flush_live(void);
extern void sve_load_from_fpsimd_state(struct user_fpsimd_state const *state,
unsigned long vq_minus_1);
diff --git a/arch/arm64/include/asm/fpsimdmacros.h b/arch/arm64/include/asm/fpsimdmacros.h
index af43367534c7..d309c6071bce 100644
--- a/arch/arm64/include/asm/fpsimdmacros.h
+++ b/arch/arm64/include/asm/fpsimdmacros.h
@@ -205,6 +205,17 @@
921:
.endm
+/* Update ZCR_EL2.LEN with the new VQ */
+.macro sve_load_vq_nvhe xvqminus1, xtmp, xtmp2
+ mrs_s \xtmp, SYS_ZCR_EL2
+ bic \xtmp2, \xtmp, ZCR_ELx_LEN_MASK
+ orr \xtmp2, \xtmp2, \xvqminus1
+ cmp \xtmp2, \xtmp
+ b.eq 922f
+ msr_s SYS_ZCR_EL2, \xtmp2 //self-synchronising
+922:
+.endm
+
/* Preserve the first 128-bits of Znz and zero the rest. */
.macro _sve_flush_z nz
_sve_check_zreg \nz
@@ -230,8 +241,7 @@
str w\nxtmp, [\xpfpsr, #4]
.endm
-.macro sve_load nxbase, xpfpsr, xvqminus1, nxtmp, xtmp2
- sve_load_vq \xvqminus1, x\nxtmp, \xtmp2
+.macro _sve_load nxbase, xpfpsr, nxtmp
_for n, 0, 31, _sve_ldr_v \n, \nxbase, \n - 34
_sve_ldr_p 0, \nxbase
_sve_wrffr 0
@@ -242,3 +252,13 @@
ldr w\nxtmp, [\xpfpsr, #4]
msr fpcr, x\nxtmp
.endm
+
+.macro sve_load nxbase, xpfpsr, xvqminus1, nxtmp, xtmp2
+ sve_load_vq \xvqminus1, x\nxtmp, \xtmp2
+ _sve_load \nxbase, \xpfpsr, \nxtmp
+.endm
+
+.macro sve_load_nvhe nxbase, xpfpsr, xvqminus1, nxtmp, xtmp2
+ sve_load_vq_nvhe \xvqminus1, x\nxtmp, \xtmp2
+ _sve_load \nxbase, \xpfpsr, \nxtmp
+.endm
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 8fcfab0c2567..11a058c81c1d 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -376,6 +376,10 @@ struct kvm_vcpu_arch {
#define vcpu_sve_pffr(vcpu) ((void *)((char *)((vcpu)->arch.sve_state) + \
sve_ffr_offset((vcpu)->arch.sve_max_vl)))
+#define vcpu_sve_pffr_hyp(vcpu) ((void *)((char *) \
+ (kern_hyp_va((vcpu)->arch.sve_state)) + \
+ sve_ffr_offset((vcpu)->arch.sve_max_vl)))
+
#define vcpu_sve_state_size(vcpu) ({ \
size_t __size_ret; \
unsigned int __vcpu_vq; \
@@ -693,19 +697,6 @@ static inline void kvm_init_host_cpu_context(struct kvm_cpu_context *cpu_ctxt)
ctxt_sys_reg(cpu_ctxt, MPIDR_EL1) = read_cpuid_mpidr();
}
-static inline bool kvm_arch_requires_vhe(void)
-{
- /*
- * The Arm architecture specifies that implementation of SVE
- * requires VHE also to be implemented. The KVM code for arm64
- * relies on this when SVE is present:
- */
- if (system_supports_sve())
- return true;
-
- return false;
-}
-
void kvm_arm_vcpu_ptrauth_trap(struct kvm_vcpu *vcpu);
static inline void kvm_arch_hardware_unsetup(void) {}
diff --git a/arch/arm64/kernel/entry-fpsimd.S b/arch/arm64/kernel/entry-fpsimd.S
index 2ca395c25448..e444b753c518 100644
--- a/arch/arm64/kernel/entry-fpsimd.S
+++ b/arch/arm64/kernel/entry-fpsimd.S
@@ -33,11 +33,6 @@ SYM_FUNC_END(fpsimd_load_state)
#ifdef CONFIG_ARM64_SVE
-SYM_FUNC_START(sve_save_state)
- sve_save 0, x1, 2
- ret
-SYM_FUNC_END(sve_save_state)
-
SYM_FUNC_START(sve_load_state)
sve_load 0, x1, x2, 3, x4
ret
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index fe60d25c000e..6284563b352a 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1890,11 +1890,6 @@ int kvm_arch_init(void *opaque)
in_hyp_mode = is_kernel_in_hyp_mode();
- if (!in_hyp_mode && kvm_arch_requires_vhe()) {
- kvm_pr_unimpl("CPU unsupported in non-VHE mode, not initializing\n");
- return -ENODEV;
- }
-
if (cpus_have_final_cap(ARM64_WORKAROUND_DEVICE_LOAD_ACQUIRE) ||
cpus_have_final_cap(ARM64_WORKAROUND_1508412))
kvm_info("Guests without required CPU erratum workarounds can deadlock system!\n" \
diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c
index 3e081d556e81..8f29b468e989 100644
--- a/arch/arm64/kvm/fpsimd.c
+++ b/arch/arm64/kvm/fpsimd.c
@@ -42,6 +42,16 @@ int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
if (ret)
goto error;
+ if (!has_vhe() && vcpu->arch.sve_state) {
+ void *sve_state_end = vcpu->arch.sve_state +
+ SVE_SIG_REGS_SIZE(
+ sve_vq_from_vl(vcpu->arch.sve_max_vl));
+ ret = create_hyp_mappings(vcpu->arch.sve_state,
+ sve_state_end,
+ 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:
@@ -109,10 +119,22 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
local_irq_save(flags);
if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED) {
+ if (guest_has_sve) {
+ if (has_vhe())
+ __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_s(SYS_ZCR_EL12);
+ else {
+ __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_s(SYS_ZCR_EL1);
+ /*
+ * vcpu could set ZCR_EL1 to a shorter VL then the max VL but
+ * the context is still valid there. Save the whole context.
+ * In nVHE case we need to reset the ZCR_EL1 for that
+ * because the save will be done in EL1.
+ */
+ write_sysreg_s(sve_vq_from_vl(vcpu->arch.sve_max_vl) - 1,
+ SYS_ZCR_EL1);
+ }
+ }
fpsimd_save_and_flush_cpu_state();
-
- if (guest_has_sve)
- __vcpu_sys_reg(vcpu, ZCR_EL1) = read_sysreg_s(SYS_ZCR_EL12);
} else if (host_has_sve) {
/*
* The FPSIMD/SVE state in the CPU has not been touched, and we
@@ -120,11 +142,14 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
* reset to CPACR_EL1_DEFAULT by the Hyp code, disabling SVE
* for EL0. To avoid spurious traps, restore the trap state
* seen by kvm_arch_vcpu_load_fp():
+ * nVHE case the CPACR_EL1 is context switched.
*/
- if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED)
- sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
- else
- sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
+ if (has_vhe()) {
+ if (vcpu->arch.flags & KVM_ARM64_HOST_SVE_ENABLED)
+ sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
+ else
+ sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
+ }
}
update_thread_flag(TIF_SVE,
diff --git a/arch/arm64/kvm/hyp/fpsimd.S b/arch/arm64/kvm/hyp/fpsimd.S
index 01f114aa47b0..da824b46b81b 100644
--- a/arch/arm64/kvm/hyp/fpsimd.S
+++ b/arch/arm64/kvm/hyp/fpsimd.S
@@ -6,6 +6,7 @@
#include <linux/linkage.h>
+#include <asm/assembler.h>
#include <asm/fpsimdmacros.h>
.text
@@ -19,3 +20,17 @@ SYM_FUNC_START(__fpsimd_restore_state)
fpsimd_restore x0, 1
ret
SYM_FUNC_END(__fpsimd_restore_state)
+
+#ifdef CONFIG_ARM64_SVE
+
+SYM_FUNC_START(sve_save_state)
+ sve_save 0, x1, 2
+ ret
+SYM_FUNC_END(sve_save_state)
+
+SYM_FUNC_START(sve_load_state_nvhe)
+ sve_load_nvhe 0, x1, x2, 3, x4
+ ret
+SYM_FUNC_END(sve_load_state_nvhe)
+
+#endif
diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 84473574c2e7..99e7f0d5bb64 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -205,19 +205,13 @@ static inline bool __hyp_handle_fpsimd(struct kvm_vcpu *vcpu)
if (!system_supports_fpsimd())
return false;
- /*
- * Currently system_supports_sve() currently implies has_vhe(),
- * so the check is redundant. However, has_vhe() can be determined
- * statically and helps the compiler remove dead code.
- */
- if (has_vhe() && system_supports_sve()) {
+ vhe = has_vhe();
+ if (system_supports_sve()) {
sve_guest = vcpu_has_sve(vcpu);
sve_host = vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE;
- vhe = true;
} else {
sve_guest = false;
sve_host = false;
- vhe = has_vhe();
}
esr_ec = kvm_vcpu_trap_get_class(vcpu);
@@ -240,17 +234,17 @@ static inline bool __hyp_handle_fpsimd(struct kvm_vcpu *vcpu)
write_sysreg(reg, cpacr_el1);
} else {
- write_sysreg(read_sysreg(cptr_el2) & ~(u64)CPTR_EL2_TFP,
- cptr_el2);
+ u64 reg = read_sysreg(cptr_el2) & ~(u64)CPTR_EL2_TFP;
+
+ if (sve_guest)
+ reg &= ~(u64)CPTR_EL2_TZ;
+
+ write_sysreg(reg, cptr_el2);
}
isb();
if (vcpu->arch.flags & KVM_ARM64_FP_HOST) {
- /*
- * In the SVE case, VHE is assumed: it is enforced by
- * Kconfig and kvm_arch_init().
- */
if (sve_host) {
struct thread_struct *thread = container_of(
vcpu->arch.host_fpsimd_state,
@@ -266,10 +260,18 @@ static inline bool __hyp_handle_fpsimd(struct kvm_vcpu *vcpu)
}
if (sve_guest) {
- sve_load_state(vcpu_sve_pffr(vcpu),
+ if (vhe) {
+ sve_load_state(vcpu_sve_pffr(vcpu),
+ &vcpu->arch.ctxt.fp_regs.fpsr,
+ sve_vq_from_vl(vcpu->arch.sve_max_vl) - 1);
+ write_sysreg_s(__vcpu_sys_reg(vcpu, ZCR_EL1), SYS_ZCR_EL12);
+ } else {
+ sve_load_state_nvhe(vcpu_sve_pffr_hyp(vcpu),
&vcpu->arch.ctxt.fp_regs.fpsr,
sve_vq_from_vl(vcpu->arch.sve_max_vl) - 1);
- write_sysreg_s(__vcpu_sys_reg(vcpu, ZCR_EL1), SYS_ZCR_EL12);
+ write_sysreg_s(__vcpu_sys_reg(vcpu, ZCR_EL1), SYS_ZCR_EL1);
+
+ }
} else {
__fpsimd_restore_state(&vcpu->arch.ctxt.fp_regs);
}
diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
index f3d0e9eca56c..df9e912d1278 100644
--- a/arch/arm64/kvm/hyp/nvhe/switch.c
+++ b/arch/arm64/kvm/hyp/nvhe/switch.c
@@ -45,6 +45,18 @@ static void __activate_traps(struct kvm_vcpu *vcpu)
if (!update_fp_enabled(vcpu)) {
val |= CPTR_EL2_TFP;
__activate_traps_fpsimd32(vcpu);
+ } else {
+ if (vcpu_has_sve(vcpu)) {
+ /*
+ * The register access will not be trapped so restore
+ * ZCR_EL1/ZCR_EL2 because those were set for the host.
+ */
+ write_sysreg_s(__vcpu_sys_reg(vcpu, ZCR_EL1), SYS_ZCR_EL1);
+ write_sysreg_s(
+ sve_vq_from_vl(vcpu->arch.sve_max_vl) - 1,
+ SYS_ZCR_EL2);
+ val &= ~CPTR_EL2_TZ;
+ }
}
write_sysreg(val, cptr_el2);
@@ -110,6 +122,17 @@ static void __load_host_stage2(void)
write_sysreg(0, vttbr_el2);
}
+static void __restore_host_sve_state(struct kvm_vcpu *vcpu)
+{
+ /*
+ * If the guest uses SVE, the ZCR_EL2 was configured for the guest.
+ * Host might save the context in EL1 but for that the ZCR_EL2 need
+ * to be reset to the host's default.
+ */
+ if (vcpu_has_sve(vcpu) && (vcpu->arch.flags |= KVM_ARM64_FP_ENABLED))
+ write_sysreg_s(ZCR_ELx_LEN_MASK, SYS_ZCR_EL2);
+}
+
/* Save VGICv3 state on non-VHE systems */
static void __hyp_vgic_save_state(struct kvm_vcpu *vcpu)
{
@@ -228,7 +251,11 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu)
__deactivate_traps(vcpu);
__load_host_stage2();
-
+ /* Host might store the SVE state in EL1 but the guest could run
+ * with different ZCR_EL2 config. It needs to be restored before
+ * returning to host EL1.
+ */
+ __restore_host_sve_state(vcpu);
__sysreg_restore_state_nvhe(host_ctxt);
if (vcpu->arch.flags & KVM_ARM64_FP_ENABLED)
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 47f3f035f3ea..17cc5e87adcd 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -74,10 +74,6 @@ static int kvm_vcpu_enable_sve(struct kvm_vcpu *vcpu)
if (!system_supports_sve())
return -EINVAL;
- /* Verify that KVM startup enforced this when SVE was detected: */
- if (WARN_ON(!has_vhe()))
- return -EINVAL;
-
vcpu->arch.sve_max_vl = kvm_sve_max_vl;
/*
@@ -113,7 +109,7 @@ static int kvm_vcpu_finalize_sve(struct kvm_vcpu *vcpu)
buf = kzalloc(SVE_SIG_REGS_SIZE(sve_vq_from_vl(vl)), GFP_KERNEL);
if (!buf)
return -ENOMEM;
-
+ __vcpu_sys_reg(vcpu, ZCR_EL1) = sve_vq_from_vl(vcpu->arch.sve_max_vl) - 1;
vcpu->arch.sve_state = buf;
vcpu->arch.flags |= KVM_ARM64_VCPU_SVE_FINALIZED;
return 0;
--
2.25.1
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