Commit cf6348af authored by Sebastian Ene's avatar Sebastian Ene Committed by Marc Zyngier
Browse files

KVM: arm64: Prevent the host from using an smc with imm16 != 0 



The ARM Service Calling Convention (SMCCC) specifies that the function
identifier and parameters should be passed in registers, leaving the
16-bit immediate field un-handled in pKVM when an SMC instruction is
trapped.
Since the HVC is a private interface between EL2 and the host,
enforce the host kernel running under pKVM to use an immediate value
of 0 only when using SMCs to make it clear for non-compliant software
talking to Trustzone that we only use SMCCC.

Signed-off-by: default avatarSebastian Ene <sebastianene@google.com>
Reviewed-by: default avatarVincent Donnefort <vdonnefort@google.com>
Link: https://patch.msgid.link/20260330105441.3226904-1-sebastianene@google.com


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent f338e773

arch/arm64/kvm/hyp/nvhe/hyp-main.c

+7 −0
Original line number Diff line number Diff line
@@ -676,8 +676,14 @@ static void default_host_smc_handler(struct kvm_cpu_context *host_ctxt) 
static void handle_host_smc(struct kvm_cpu_context *host_ctxt)

{

	DECLARE_REG(u64, func_id, host_ctxt, 0);

	u64 esr = read_sysreg_el2(SYS_ESR);

	bool handled;



	if (esr & ESR_ELx_xVC_IMM_MASK) {

		cpu_reg(host_ctxt, 0) = SMCCC_RET_NOT_SUPPORTED;

		goto exit_skip_instr;

	}



	func_id &= ~ARM_SMCCC_CALL_HINTS;



	handled = kvm_host_psci_handler(host_ctxt, func_id);
@@ -686,6 +692,7 @@ static void handle_host_smc(struct kvm_cpu_context *host_ctxt) 
	if (!handled)

		default_host_smc_handler(host_ctxt);



exit_skip_instr:

	/* SMC was trapped, move ELR past the current PC. */

	kvm_skip_host_instr();

}