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Commit f99e4064 authored by Marc Zyngier's avatar Marc Zyngier Committed by Greg Kroah-Hartman
Browse files

arm64: KVM: Handle guest's ARCH_WORKAROUND_2 requests 



commit b4f18c063a13dfb33e3a63fe1844823e19c2265e upstream.

In order to forward the guest's ARCH_WORKAROUND_2 calls to EL3,
add a small(-ish) sequence to handle it at EL2. Special care must
be taken to track the state of the guest itself by updating the
workaround flags. We also rely on patching to enable calls into
the firmware.

Note that since we need to execute branches, this always executes
after the Spectre-v2 mitigation has been applied.

Reviewed-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Signed-off-by: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 68240e9b

arch/arm64/kernel/asm-offsets.c

+1 −0
Original line number Diff line number Diff line
@@ -127,6 +127,7 @@ int main(void) 
  BLANK();

#ifdef CONFIG_KVM_ARM_HOST

  DEFINE(VCPU_CONTEXT,		offsetof(struct kvm_vcpu, arch.ctxt));

  DEFINE(VCPU_WORKAROUND_FLAGS,	offsetof(struct kvm_vcpu, arch.workaround_flags));

  DEFINE(CPU_GP_REGS,		offsetof(struct kvm_cpu_context, gp_regs));

  DEFINE(CPU_USER_PT_REGS,	offsetof(struct kvm_regs, regs));

  DEFINE(CPU_FP_REGS,		offsetof(struct kvm_regs, fp_regs));

arch/arm64/kvm/hyp/hyp-entry.S

+37 −1
Original line number Diff line number Diff line
@@ -107,8 +107,44 @@ el1_hvc_guest: 
	 */

	ldr	x1, [sp]				// Guest's x0

	eor	w1, w1, #ARM_SMCCC_ARCH_WORKAROUND_1

	cbz	w1, wa_epilogue



	/* ARM_SMCCC_ARCH_WORKAROUND_2 handling */

	eor	w1, w1, #(ARM_SMCCC_ARCH_WORKAROUND_1 ^ \

			  ARM_SMCCC_ARCH_WORKAROUND_2)

	cbnz	w1, el1_trap

	mov	x0, x1



#ifdef CONFIG_ARM64_SSBD

alternative_cb	arm64_enable_wa2_handling

	b	wa2_end

alternative_cb_end

	get_vcpu_ptr	x2, x0

	ldr	x0, [x2, #VCPU_WORKAROUND_FLAGS]



	// Sanitize the argument and update the guest flags

	ldr	x1, [sp, #8]			// Guest's x1

	clz	w1, w1				// Murphy's device:

	lsr	w1, w1, #5			// w1 = !!w1 without using

	eor	w1, w1, #1			// the flags...

	bfi	x0, x1, #VCPU_WORKAROUND_2_FLAG_SHIFT, #1

	str	x0, [x2, #VCPU_WORKAROUND_FLAGS]



	/* Check that we actually need to perform the call */

	hyp_ldr_this_cpu x0, arm64_ssbd_callback_required, x2

	cbz	x0, wa2_end



	mov	w0, #ARM_SMCCC_ARCH_WORKAROUND_2

	smc	#0



	/* Don't leak data from the SMC call */

	mov	x3, xzr

wa2_end:

	mov	x2, xzr

	mov	x1, xzr

#endif



wa_epilogue:

	mov	x0, xzr

	add	sp, sp, #16

	eret