Commit 7d894834 authored by Yanan Wang's avatar Yanan Wang Committed by Marc Zyngier
Browse files

KVM: arm64: Add usage of stage 2 fault lookup level in user_mem_abort() 



If we get a FSC_PERM fault, just using (logging_active && writable) to
determine calling kvm_pgtable_stage2_map(). There will be two more cases
we should consider.

(1) After logging_active is configged back to false from true. When we
get a FSC_PERM fault with write_fault and adjustment of hugepage is needed,
we should merge tables back to a block entry. This case is ignored by still
calling kvm_pgtable_stage2_relax_perms(), which will lead to an endless
loop and guest panic due to soft lockup.

(2) We use (FSC_PERM && logging_active && writable) to determine
collapsing a block entry into a table by calling kvm_pgtable_stage2_map().
But sometimes we may only need to relax permissions when trying to write
to a page other than a block.
In this condition,using kvm_pgtable_stage2_relax_perms() will be fine.

The ISS filed bit[1:0] in ESR_EL2 regesiter indicates the stage2 lookup
level at which a D-abort or I-abort occurred. By comparing granule of
the fault lookup level with vma_pagesize, we can strictly distinguish
conditions of calling kvm_pgtable_stage2_relax_perms() or
kvm_pgtable_stage2_map(), and the above two cases will be well considered.

Suggested-by: default avatarKeqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: default avatarYanan Wang <wangyanan55@huawei.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Acked-by: default avatarWill Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201201201034.116760-4-wangyanan55@huawei.com
parent 3a0b870e

arch/arm64/include/asm/esr.h

+1 −0
Original line number Diff line number Diff line
@@ -104,6 +104,7 @@ 
/* Shared ISS fault status code(IFSC/DFSC) for Data/Instruction aborts */

#define ESR_ELx_FSC		(0x3F)

#define ESR_ELx_FSC_TYPE	(0x3C)

#define ESR_ELx_FSC_LEVEL	(0x03)

#define ESR_ELx_FSC_EXTABT	(0x10)

#define ESR_ELx_FSC_SERROR	(0x11)

#define ESR_ELx_FSC_ACCESS	(0x08)

arch/arm64/include/asm/kvm_emulate.h

+5 −0
Original line number Diff line number Diff line
@@ -350,6 +350,11 @@ static __always_inline u8 kvm_vcpu_trap_get_fault_type(const struct kvm_vcpu *vc 
	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_FSC_TYPE;

}



static __always_inline u8 kvm_vcpu_trap_get_fault_level(const struct kvm_vcpu *vcpu)

{

	return kvm_vcpu_get_esr(vcpu) & ESR_ELx_FSC_LEVEL;

}



static __always_inline bool kvm_vcpu_abt_issea(const struct kvm_vcpu *vcpu)

{

	switch (kvm_vcpu_trap_get_fault(vcpu)) {

arch/arm64/kvm/mmu.c

+9 −2
Original line number Diff line number Diff line
@@ -754,10 +754,12 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, 
	gfn_t gfn;

	kvm_pfn_t pfn;

	bool logging_active = memslot_is_logging(memslot);

	unsigned long vma_pagesize;

	unsigned long fault_level = kvm_vcpu_trap_get_fault_level(vcpu);

	unsigned long vma_pagesize, fault_granule;

	enum kvm_pgtable_prot prot = KVM_PGTABLE_PROT_R;

	struct kvm_pgtable *pgt;



	fault_granule = 1UL << ARM64_HW_PGTABLE_LEVEL_SHIFT(fault_level);

	write_fault = kvm_is_write_fault(vcpu);

	exec_fault = kvm_vcpu_trap_is_exec_fault(vcpu);

	VM_BUG_ON(write_fault && exec_fault);
@@ -896,7 +898,12 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, 
	else if (cpus_have_const_cap(ARM64_HAS_CACHE_DIC))

		prot |= KVM_PGTABLE_PROT_X;



	if (fault_status == FSC_PERM && !(logging_active && writable)) {

	/*

	 * Under the premise of getting a FSC_PERM fault, we just need to relax

	 * permissions only if vma_pagesize equals fault_granule. Otherwise,

	 * kvm_pgtable_stage2_map() should be called to change block size.

	 */

	if (fault_status == FSC_PERM && vma_pagesize == fault_granule) {

		ret = kvm_pgtable_stage2_relax_perms(pgt, fault_ipa, prot);

	} else {

		ret = kvm_pgtable_stage2_map(pgt, fault_ipa, vma_pagesize,

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