[PATCH 1/2] KVM: arm64: Introduce KVM_PGTABLE_S2_NOFWB Stage-2 flag
From: Quentin Perret
Date: Wed Mar 17 2021 - 10:17:56 EST
In order to further configure stage-2 page-tables, pass flags to the
init function using a new enum.
The first of these flags allows to disable FWB even if the hardware
supports it as we will need to do so for the host stage-2.
Signed-off-by: Quentin Perret <qperret@xxxxxxxxxx>
---
One question is, do we want to use stage2_has_fwb() everywhere, including
guest-specific paths (e.g. kvm_arch_prepare_memory_region(), ...) ?
That'd make this patch more intrusive, but would make the whole codebase
work with FWB enabled on a guest by guest basis. I don't see us use that
anytime soon (other than maybe debug of some sort?) but it'd be good to
have an agreement.
---
arch/arm64/include/asm/kvm_pgtable.h | 19 +++++++++--
arch/arm64/include/asm/pgtable-prot.h | 4 +--
arch/arm64/kvm/hyp/pgtable.c | 49 +++++++++++++++++----------
3 files changed, 50 insertions(+), 22 deletions(-)
diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
index b93a2a3526ab..7382bdfb6284 100644
--- a/arch/arm64/include/asm/kvm_pgtable.h
+++ b/arch/arm64/include/asm/kvm_pgtable.h
@@ -56,6 +56,15 @@ struct kvm_pgtable_mm_ops {
phys_addr_t (*virt_to_phys)(void *addr);
};
+/**
+ * enum kvm_pgtable_stage2_flags - Stage-2 page-table flags.
+ * @KVM_PGTABLE_S2_NOFWB: Don't enforce Normal-WB even if the CPUs have
+ * ARM64_HAS_STAGE2_FWB.
+ */
+enum kvm_pgtable_stage2_flags {
+ KVM_PGTABLE_S2_NOFWB = BIT(0),
+};
+
/**
* struct kvm_pgtable - KVM page-table.
* @ia_bits: Maximum input address size, in bits.
@@ -72,6 +81,7 @@ struct kvm_pgtable {
/* Stage-2 only */
struct kvm_s2_mmu *mmu;
+ enum kvm_pgtable_stage2_flags flags;
};
/**
@@ -201,11 +211,16 @@ u64 kvm_get_vtcr(u64 mmfr0, u64 mmfr1, u32 phys_shift);
* @arch: Arch-specific KVM structure representing the guest virtual
* machine.
* @mm_ops: Memory management callbacks.
+ * @flags: Stage-2 configuration flags.
*
* Return: 0 on success, negative error code on failure.
*/
-int kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_arch *arch,
- struct kvm_pgtable_mm_ops *mm_ops);
+int kvm_pgtable_stage2_init_flags(struct kvm_pgtable *pgt, struct kvm_arch *arch,
+ struct kvm_pgtable_mm_ops *mm_ops,
+ enum kvm_pgtable_stage2_flags flags);
+
+#define kvm_pgtable_stage2_init(pgt, arch, mm_ops) \
+ kvm_pgtable_stage2_init_flags(pgt, arch, mm_ops, 0)
/**
* kvm_pgtable_stage2_destroy() - Destroy an unused guest stage-2 page-table.
diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
index 046be789fbb4..beeb722a82d3 100644
--- a/arch/arm64/include/asm/pgtable-prot.h
+++ b/arch/arm64/include/asm/pgtable-prot.h
@@ -72,10 +72,10 @@ extern bool arm64_use_ng_mappings;
#define PAGE_KERNEL_EXEC __pgprot(PROT_NORMAL & ~PTE_PXN)
#define PAGE_KERNEL_EXEC_CONT __pgprot((PROT_NORMAL & ~PTE_PXN) | PTE_CONT)
-#define PAGE_S2_MEMATTR(attr) \
+#define PAGE_S2_MEMATTR(attr, has_fwb) \
({ \
u64 __val; \
- if (cpus_have_const_cap(ARM64_HAS_STAGE2_FWB)) \
+ if (has_fwb) \
__val = PTE_S2_MEMATTR(MT_S2_FWB_ ## attr); \
else \
__val = PTE_S2_MEMATTR(MT_S2_ ## attr); \
diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
index 3a971df278bd..dee8aaeaf13e 100644
--- a/arch/arm64/kvm/hyp/pgtable.c
+++ b/arch/arm64/kvm/hyp/pgtable.c
@@ -507,12 +507,25 @@ u64 kvm_get_vtcr(u64 mmfr0, u64 mmfr1, u32 phys_shift)
return vtcr;
}
-static int stage2_set_prot_attr(enum kvm_pgtable_prot prot, kvm_pte_t *ptep)
+static bool stage2_has_fwb(struct kvm_pgtable *pgt)
+{
+ if (!cpus_have_const_cap(ARM64_HAS_STAGE2_FWB))
+ return false;
+
+ return !(pgt->flags & KVM_PGTABLE_S2_NOFWB);
+}
+
+static int stage2_set_prot_attr(enum kvm_pgtable_prot prot, kvm_pte_t *ptep,
+ struct kvm_pgtable *pgt)
{
bool device = prot & KVM_PGTABLE_PROT_DEVICE;
- kvm_pte_t attr = device ? PAGE_S2_MEMATTR(DEVICE_nGnRE) :
- PAGE_S2_MEMATTR(NORMAL);
u32 sh = KVM_PTE_LEAF_ATTR_LO_S2_SH_IS;
+ kvm_pte_t attr;
+
+ if (device)
+ attr = PAGE_S2_MEMATTR(DEVICE_nGnRE, stage2_has_fwb(pgt));
+ else
+ attr = PAGE_S2_MEMATTR(NORMAL, stage2_has_fwb(pgt));
if (!(prot & KVM_PGTABLE_PROT_X))
attr |= KVM_PTE_LEAF_ATTR_HI_S2_XN;
@@ -748,7 +761,7 @@ int kvm_pgtable_stage2_map(struct kvm_pgtable *pgt, u64 addr, u64 size,
.arg = &map_data,
};
- ret = stage2_set_prot_attr(prot, &map_data.attr);
+ ret = stage2_set_prot_attr(prot, &map_data.attr, pgt);
if (ret)
return ret;
@@ -786,16 +799,13 @@ int kvm_pgtable_stage2_set_owner(struct kvm_pgtable *pgt, u64 addr, u64 size,
static void stage2_flush_dcache(void *addr, u64 size)
{
- if (cpus_have_const_cap(ARM64_HAS_STAGE2_FWB))
- return;
-
__flush_dcache_area(addr, size);
}
-static bool stage2_pte_cacheable(kvm_pte_t pte)
+static bool stage2_pte_cacheable(kvm_pte_t pte, struct kvm_pgtable *pgt)
{
u64 memattr = pte & KVM_PTE_LEAF_ATTR_LO_S2_MEMATTR;
- return memattr == PAGE_S2_MEMATTR(NORMAL);
+ return memattr == PAGE_S2_MEMATTR(NORMAL, stage2_has_fwb(pgt));
}
static int stage2_unmap_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
@@ -821,8 +831,8 @@ static int stage2_unmap_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
if (mm_ops->page_count(childp) != 1)
return 0;
- } else if (stage2_pte_cacheable(pte)) {
- need_flush = true;
+ } else if (stage2_pte_cacheable(pte, pgt)) {
+ need_flush = !stage2_has_fwb(pgt);
}
/*
@@ -979,10 +989,11 @@ static int stage2_flush_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
enum kvm_pgtable_walk_flags flag,
void * const arg)
{
- struct kvm_pgtable_mm_ops *mm_ops = arg;
+ struct kvm_pgtable *pgt = arg;
+ struct kvm_pgtable_mm_ops *mm_ops = pgt->mm_ops;
kvm_pte_t pte = *ptep;
- if (!kvm_pte_valid(pte) || !stage2_pte_cacheable(pte))
+ if (!kvm_pte_valid(pte) || !stage2_pte_cacheable(pte, pgt))
return 0;
stage2_flush_dcache(kvm_pte_follow(pte, mm_ops), kvm_granule_size(level));
@@ -994,17 +1005,18 @@ int kvm_pgtable_stage2_flush(struct kvm_pgtable *pgt, u64 addr, u64 size)
struct kvm_pgtable_walker walker = {
.cb = stage2_flush_walker,
.flags = KVM_PGTABLE_WALK_LEAF,
- .arg = pgt->mm_ops,
+ .arg = pgt,
};
- if (cpus_have_const_cap(ARM64_HAS_STAGE2_FWB))
+ if (stage2_has_fwb(pgt))
return 0;
return kvm_pgtable_walk(pgt, addr, size, &walker);
}
-int kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_arch *arch,
- struct kvm_pgtable_mm_ops *mm_ops)
+int kvm_pgtable_stage2_init_flags(struct kvm_pgtable *pgt, struct kvm_arch *arch,
+ struct kvm_pgtable_mm_ops *mm_ops,
+ enum kvm_pgtable_stage2_flags flags)
{
size_t pgd_sz;
u64 vtcr = arch->vtcr;
@@ -1017,6 +1029,7 @@ int kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_arch *arch,
if (!pgt->pgd)
return -ENOMEM;
+ pgt->flags = flags;
pgt->ia_bits = ia_bits;
pgt->start_level = start_level;
pgt->mm_ops = mm_ops;
@@ -1101,7 +1114,7 @@ int kvm_pgtable_stage2_find_range(struct kvm_pgtable *pgt, u64 addr,
u32 level;
int ret;
- ret = stage2_set_prot_attr(prot, &attr);
+ ret = stage2_set_prot_attr(prot, &attr, pgt);
if (ret)
return ret;
attr &= KVM_PTE_LEAF_S2_COMPAT_MASK;
--
2.31.0.rc2.261.g7f71774620-goog