Commit 73c55be0 authored by Will Deacon's avatar Will Deacon Committed by Marc Zyngier
Browse files

KVM: arm64: Ignore -EAGAIN when mapping in pages for the pKVM host 



If the host takes a stage-2 translation fault on two CPUs at the same
time, one of them will get back -EAGAIN from the page-table mapping code
when it runs into the mapping installed by the other.

Rather than handle this explicitly in handle_host_mem_abort(), pass the
new KVM_PGTABLE_WALK_IGNORE_EAGAIN flag to kvm_pgtable_stage2_map() from
__host_stage2_idmap() and return -EEXIST if host_stage2_adjust_range()
finds a valid pte. This will avoid having to test for -EAGAIN on the
reclaim path in subsequent patches.

Reviewed-by: default avatarFuad Tabba <tabba@google.com>
Tested-by: default avatarFuad Tabba <tabba@google.com>
Tested-by: default avatarMostafa Saleh <smostafa@google.com>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
Link: https://patch.msgid.link/20260330144841.26181-11-will@kernel.org


Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent f0877a14

arch/arm64/kvm/hyp/nvhe/mem_protect.c

+16 −5
Original line number Diff line number Diff line
@@ -461,8 +461,15 @@ static bool range_is_memory(u64 start, u64 end) 
static inline int __host_stage2_idmap(u64 start, u64 end,

				      enum kvm_pgtable_prot prot)

{

	/*

	 * We don't make permission changes to the host idmap after

	 * initialisation, so we can squash -EAGAIN to save callers

	 * having to treat it like success in the case that they try to

	 * map something that is already mapped.

	 */

	return kvm_pgtable_stage2_map(&host_mmu.pgt, start, end - start, start,

				      prot, &host_s2_pool, 0);

				      prot, &host_s2_pool,

				      KVM_PGTABLE_WALK_IGNORE_EAGAIN);

}



/*
@@ -504,7 +511,7 @@ static int host_stage2_adjust_range(u64 addr, struct kvm_mem_range *range) 
		return ret;



	if (kvm_pte_valid(pte))

		return -EAGAIN;

		return -EEXIST;



	if (pte) {

		WARN_ON(addr_is_memory(addr) &&
@@ -609,7 +616,6 @@ void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt) 
{

	struct kvm_vcpu_fault_info fault;

	u64 esr, addr;

	int ret = 0;



	esr = read_sysreg_el2(SYS_ESR);

	if (!__get_fault_info(esr, &fault)) {
@@ -628,8 +634,13 @@ void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt) 
	BUG_ON(!(fault.hpfar_el2 & HPFAR_EL2_NS));

	addr = FIELD_GET(HPFAR_EL2_FIPA, fault.hpfar_el2) << 12;



	ret = host_stage2_idmap(addr);

	BUG_ON(ret && ret != -EAGAIN);

	switch (host_stage2_idmap(addr)) {

	case -EEXIST:

	case 0:

		break;

	default:

		BUG();

	}

}



struct check_walk_data {