| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20260106102040.25041-1-yan.y.zhao@intel.com>
Date: Tue, 6 Jan 2026 18:20:40 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: pbonzini@...hat.com,
seanjc@...gle.com
Cc: linux-kernel@...r.kernel.org,
kvm@...r.kernel.org,
x86@...nel.org,
rick.p.edgecombe@...el.com,
dave.hansen@...el.com,
kas@...nel.org,
tabba@...gle.com,
ackerleytng@...gle.com,
michael.roth@....com,
david@...nel.org,
vannapurve@...gle.com,
sagis@...gle.com,
vbabka@...e.cz,
thomas.lendacky@....com,
nik.borisov@...e.com,
pgonda@...gle.com,
fan.du@...el.com,
jun.miao@...el.com,
francescolavra.fl@...il.com,
jgross@...e.com,
ira.weiny@...el.com,
isaku.yamahata@...el.com,
xiaoyao.li@...el.com,
kai.huang@...el.com,
binbin.wu@...ux.intel.com,
chao.p.peng@...el.com,
chao.gao@...el.com,
yan.y.zhao@...el.com
Subject: [PATCH v3 07/24] KVM: x86/tdp_mmu: Introduce split_external_spte() under write mmu_lock
Introduce kvm_x86_ops.split_external_spte() and wrap it in a helper
function split_external_spte(). Invoke the helper function
split_external_spte() in tdp_mmu_set_spte() to propagate splitting
transitions from the mirror page table to the external page table under
write mmu_lock.
Introduce a new valid transition case for splitting and document all valid
transitions of the mirror page table under write mmu_lock in
tdp_mmu_set_spte().
Signed-off-by: Xiaoyao Li <xiaoyao.li@...el.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
---
v3:
- Rename split_external_spt() to split_external_spte().
- Pass in param "old_mirror_spte" to hook kvm_x86_ops.set_external_spte().
This is in aligned with the parameter change in hook
kvm_x86_ops.set_external_spte() in Sean's cleanup series, and also allows
future DPAMT patches to acquire guest private PFN from the old mirror
spte.
- Rename param "external_spt" to "new_external_spt" in hook
kvm_x86_ops.set_external_spte() to indicate this is a new page table page
for the external page table.
- Drop declaration of get_external_spt() by moving split_external_spte()
after get_external_spt() but before set_external_spte_present() and
tdp_mmu_set_spte(). (Kai)
- split_external_spte --> split_external_spte() (Kai)
RFC v2:
- Removed the KVM_BUG_ON() in split_external_spt(). (Rick)
- Add a comment for the KVM_BUG_ON() in tdp_mmu_set_spte(). (Rick)
- Use kvm_x86_call() instead of static_call(). (Binbin)
RFC v1:
- Split patch.
- Dropped invoking hook zap_private_spte and kvm_flush_remote_tlbs() in KVM
MMU core.
---
arch/x86/include/asm/kvm-x86-ops.h | 1 +
arch/x86/include/asm/kvm_host.h | 4 ++++
arch/x86/kvm/mmu/tdp_mmu.c | 29 +++++++++++++++++++++++++----
3 files changed, 30 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 58c5c9b082ca..84fa8689b45c 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -98,6 +98,7 @@ KVM_X86_OP_OPTIONAL(link_external_spt)
KVM_X86_OP_OPTIONAL(set_external_spte)
KVM_X86_OP_OPTIONAL(free_external_spt)
KVM_X86_OP_OPTIONAL(remove_external_spte)
+KVM_X86_OP_OPTIONAL(split_external_spte)
KVM_X86_OP_OPTIONAL(alloc_external_fault_cache)
KVM_X86_OP_OPTIONAL(topup_external_fault_cache)
KVM_X86_OP_OPTIONAL(free_external_fault_cache)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 7818da148a8c..56089d6b9b51 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1848,6 +1848,10 @@ struct kvm_x86_ops {
void (*remove_external_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
u64 mirror_spte);
+ /* Split a huge mapping into smaller mappings in external page table */
+ int (*split_external_spte)(struct kvm *kvm, gfn_t gfn, enum pg_level level,
+ u64 old_mirror_spte, void *new_external_spt);
+
/* Allocation a pages from the external page cache. */
void *(*alloc_external_fault_cache)(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index dfa56554f9e0..977914b2627f 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -508,6 +508,19 @@ static void *get_external_spt(gfn_t gfn, u64 new_spte, int level)
return NULL;
}
+static int split_external_spte(struct kvm *kvm, gfn_t gfn, u64 old_spte,
+ u64 new_spte, int level)
+{
+ void *new_external_spt = get_external_spt(gfn, new_spte, level);
+ int ret;
+
+ KVM_BUG_ON(!new_external_spt, kvm);
+
+ ret = kvm_x86_call(split_external_spte)(kvm, gfn, level, old_spte,
+ new_external_spt);
+ return ret;
+}
+
static int __must_check set_external_spte_present(struct kvm *kvm, tdp_ptep_t sptep,
gfn_t gfn, u64 old_spte,
u64 new_spte, int level)
@@ -758,12 +771,20 @@ static u64 tdp_mmu_set_spte(struct kvm *kvm, int as_id, tdp_ptep_t sptep,
handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, level, false);
/*
- * Users that do non-atomic setting of PTEs don't operate on mirror
- * roots, so don't handle it and bug the VM if it's seen.
+ * Propagate changes of SPTE to the external page table under write
+ * mmu_lock.
+ * Current valid transitions:
+ * - present leaf to !present.
+ * - present non-leaf to !present.
+ * - present leaf to present non-leaf (splitting)
*/
if (is_mirror_sptep(sptep)) {
- KVM_BUG_ON(is_shadow_present_pte(new_spte), kvm);
- remove_external_spte(kvm, gfn, old_spte, level);
+ if (!is_shadow_present_pte(new_spte))
+ remove_external_spte(kvm, gfn, old_spte, level);
+ else if (is_last_spte(old_spte, level) && !is_last_spte(new_spte, level))
+ split_external_spte(kvm, gfn, old_spte, new_spte, level);
+ else
+ KVM_BUG_ON(1, kvm);
}
return old_spte;
--
2.43.2
Powered by blists - more mailing lists