Commit ed648ab8 authored by Marc Zyngier's avatar Marc Zyngier
Browse files

KVM: arm64: Teach address translation about access faults 



It appears that our S1 PTW is completely oblivious of access faults.
Teach the S1 translation code about it.

Reviewed-by: default avatarJoey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/r/20250422122612.2675672-3-maz@kernel.org


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent 493b01de

arch/arm64/kvm/at.c

+21 −5
Original line number Diff line number Diff line
@@ -456,6 +456,11 @@ static int walk_s1(struct kvm_vcpu *vcpu, struct s1_walk_info *wi, 
	if (check_output_size(desc & GENMASK(47, va_bottom), wi))

		goto addrsz;



	if (!(desc & PTE_AF)) {

		fail_s1_walk(wr, ESR_ELx_FSC_ACCESS_L(level), false);

		return -EACCES;

	}



	va_bottom += contiguous_bit_shift(desc, wi, level);



	wr->failed = false;
@@ -1209,7 +1214,8 @@ static u64 handle_at_slow(struct kvm_vcpu *vcpu, u32 op, u64 vaddr) 
 * If the translation is unsuccessful, the value may only contain

 * PAR_EL1.F, and cannot be taken at face value. It isn't an

 * indication of the translation having failed, only that the fast

 * path did not succeed, *unless* it indicates a S1 permission fault.

 * path did not succeed, *unless* it indicates a S1 permission or

 * access fault.

 */

static u64 __kvm_at_s1e01_fast(struct kvm_vcpu *vcpu, u32 op, u64 vaddr)

{
@@ -1312,19 +1318,29 @@ static bool par_check_s1_perm_fault(u64 par) 
		 !(par & SYS_PAR_EL1_S));

}



static bool par_check_s1_access_fault(u64 par)

{

	u8 fst = FIELD_GET(SYS_PAR_EL1_FST, par);



	return  ((fst & ESR_ELx_FSC_TYPE) == ESR_ELx_FSC_ACCESS &&

		 !(par & SYS_PAR_EL1_S));

}



void __kvm_at_s1e01(struct kvm_vcpu *vcpu, u32 op, u64 vaddr)

{

	u64 par = __kvm_at_s1e01_fast(vcpu, op, vaddr);



	/*

	 * If PAR_EL1 reports that AT failed on a S1 permission fault, we

	 * know for sure that the PTW was able to walk the S1 tables and

	 * there's nothing else to do.

	 * If PAR_EL1 reports that AT failed on a S1 permission or access

	 * fault, we know for sure that the PTW was able to walk the S1

	 * tables and there's nothing else to do.

	 *

	 * If AT failed for any other reason, then we must walk the guest S1

	 * to emulate the instruction.

	 */

	if ((par & SYS_PAR_EL1_F) && !par_check_s1_perm_fault(par))

	if ((par & SYS_PAR_EL1_F) &&

	    !par_check_s1_perm_fault(par) &&

	    !par_check_s1_access_fault(par))

		par = handle_at_slow(vcpu, op, vaddr);



	vcpu_write_sys_reg(vcpu, par, PAR_EL1);