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arm64: KVM: Handle guest's ARCH_WORKAROUND_2 requests 

commit b4f18c063a 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: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
pull/10/head
Marc Zyngier 2018-07-20 10:53:11 +01:00 committed by Greg Kroah-Hartman
parent 805357aa65
commit 1b749f8a24
2 changed files with 38 additions and 1 deletions
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1
arch/arm64/kernel/asm-offsets.c
View File

@ -131,6 +131,7 @@ 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));

38
arch/arm64/kvm/hyp/hyp-entry.S
View File

@ -106,8 +106,44 @@ 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