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: Keqian Zhu <zhukeqian1@huawei.com>
Signed-off-by: Yanan Wang <wangyanan55@huawei.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20201201201034.116760-4-wangyanan55@huawei.com

diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h
index 22c81f1edda2a18496d254865c07e84d01eb5a2c..85a3e49f92f4aadf4724a3f4a830f8362ad7cbf3 100644 (file)
--- a/arch/arm64/include/asm/esr.h
+++ b/arch/arm64/include/asm/esr.h
@@ -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)

diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
index 5ef2669ccd6c3908bdc64d82cc7ac342de19b1b3..00bc6f1234ba3e6329bc7be7a0fc1cd3b6133da2 100644 (file)
--- a/arch/arm64/include/asm/kvm_emulate.h
+++ b/arch/arm64/include/asm/kvm_emulate.h
@@ -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)) {

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 1a01da9fdc99cd11a9912c31e4893d94cf070cb4..75814a02d1894b1fdcac2b87b81d831aae6b4212 100644 (file)
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -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,