Commit 85acda3b authored by Dave Martin's avatar Dave Martin Committed by Marc Zyngier
Browse files

KVM: arm64: Save host SVE context as appropriate 



This patch adds SVE context saving to the hyp FPSIMD context switch
path.  This means that it is no longer necessary to save the host
SVE state in advance of entering the guest, when in use.

In order to avoid adding pointless complexity to the code, VHE is
assumed if SVE is in use.  VHE is an architectural prerequisite for
SVE, so there is no good reason to turn CONFIG_ARM64_VHE off in
kernels that support both SVE and KVM.

Historically, software models exist that can expose the
architecturally invalid configuration of SVE without VHE, so if
this situation is detected at kvm_init() time then KVM will be
disabled.

Signed-off-by: default avatarDave Martin <Dave.Martin@arm.com>
Reviewed-by: default avatarAlex Bennée <alex.bennee@linaro.org>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
parent 9a6e5948

arch/arm/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -280,6 +280,7 @@ void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot); 


struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);



static inline bool kvm_arch_check_sve_has_vhe(void) { return true; }

static inline void kvm_arch_hardware_unsetup(void) {}

static inline void kvm_arch_sync_events(struct kvm *kvm) {}

static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}

arch/arm64/Kconfig

+7 −0
Original line number Diff line number Diff line
@@ -1130,6 +1130,7 @@ 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
@@ -1155,6 +1156,12 @@ 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

	select HAVE_MOD_ARCH_SPECIFIC

arch/arm64/include/asm/kvm_host.h

+13 −0
Original line number Diff line number Diff line
@@ -405,6 +405,19 @@ static inline void __cpu_init_hyp_mode(phys_addr_t pgd_ptr, 
	kvm_call_hyp(__kvm_set_tpidr_el2, tpidr_el2);

}



static inline bool kvm_arch_check_sve_has_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 has_vhe();

	else

		return true;

}



static inline void kvm_arch_hardware_unsetup(void) {}

static inline void kvm_arch_sync_events(struct kvm *kvm) {}

static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}

arch/arm64/kvm/fpsimd.c

+0 −1
Original line number Diff line number Diff line
@@ -59,7 +59,6 @@ error: 
 */

void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)

{

	BUG_ON(system_supports_sve());

	BUG_ON(!current->mm);



	vcpu->arch.flags &= ~(KVM_ARM64_FP_ENABLED | KVM_ARM64_HOST_SVE_IN_USE);

arch/arm64/kvm/hyp/switch.c

+19 −1
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 


#include <kvm/arm_psci.h>



#include <asm/cpufeature.h>

#include <asm/kvm_asm.h>

#include <asm/kvm_emulate.h>

#include <asm/kvm_host.h>
@@ -28,6 +29,7 @@ 
#include <asm/kvm_mmu.h>

#include <asm/fpsimd.h>

#include <asm/debug-monitors.h>

#include <asm/processor.h>

#include <asm/thread_info.h>



/* Check whether the FP regs were dirtied while in the host-side run loop: */
@@ -329,6 +331,8 @@ static bool __hyp_text __skip_instr(struct kvm_vcpu *vcpu) 
void __hyp_text __hyp_switch_fpsimd(u64 esr __always_unused,

				    struct kvm_vcpu *vcpu)

{

	struct user_fpsimd_state *host_fpsimd = vcpu->arch.host_fpsimd_state;



	if (has_vhe())

		write_sysreg(read_sysreg(cpacr_el1) | CPACR_EL1_FPEN,

			     cpacr_el1);
@@ -339,7 +343,21 @@ void __hyp_text __hyp_switch_fpsimd(u64 esr __always_unused, 
	isb();



	if (vcpu->arch.flags & KVM_ARM64_FP_HOST) {

		__fpsimd_save_state(vcpu->arch.host_fpsimd_state);

		/*

		 * In the SVE case, VHE is assumed: it is enforced by

		 * Kconfig and kvm_arch_init().

		 */

		if (system_supports_sve() &&

		    (vcpu->arch.flags & KVM_ARM64_HOST_SVE_IN_USE)) {

			struct thread_struct *thread = container_of(

				host_fpsimd,

				struct thread_struct, uw.fpsimd_state);



			sve_save_state(sve_pffr(thread), &host_fpsimd->fpsr);

		} else {

			__fpsimd_save_state(host_fpsimd);

		}



		vcpu->arch.flags &= ~KVM_ARM64_FP_HOST;

	}

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