From: Junaid Shahid <junaids@google.com>
To: linux-kernel@vger.kernel.org
Cc: Ofir Weisse <oweisse@google.com>,
kvm@vger.kernel.org, pbonzini@redhat.com, jmattson@google.com,
pjt@google.com, alexandre.chartre@oracle.com, rppt@linux.ibm.com,
dave.hansen@linux.intel.com, peterz@infradead.org,
tglx@linutronix.de, luto@kernel.org, linux-mm@kvack.org
Subject: [RFC PATCH 22/47] mm: asi: Added refcounting when initilizing an asi
Date: Tue, 22 Feb 2022 21:21:58 -0800 [thread overview]
Message-ID: <20220223052223.1202152-23-junaids@google.com> (raw)
In-Reply-To: <20220223052223.1202152-1-junaids@google.com>
From: Ofir Weisse <oweisse@google.com>
Some KVM tests initilize multiple VMs in a single process. For these
cases, we want to suppurt multiple callse to asi_init() before a single
asi_destroy is called. We want the initilization to happen exactly once.
IF asi_destroy() is called, release the resources only if the counter
reached zero. In our current implementation, asi's are tied to
a specific mm. This may change in a future implementation. In which
case, the mutex for the refcounting will need to move to struct asi.
Signed-off-by: Ofir Weisse <oweisse@google.com>
---
arch/x86/include/asm/asi.h | 1 +
arch/x86/mm/asi.c | 52 +++++++++++++++++++++++++++++++++-----
include/linux/mm_types.h | 2 ++
kernel/fork.c | 3 +++
4 files changed, 51 insertions(+), 7 deletions(-)
diff --git a/arch/x86/include/asm/asi.h b/arch/x86/include/asm/asi.h
index e3cbf6d8801e..2dc465f78bcc 100644
--- a/arch/x86/include/asm/asi.h
+++ b/arch/x86/include/asm/asi.h
@@ -40,6 +40,7 @@ struct asi {
pgd_t *pgd;
struct asi_class *class;
struct mm_struct *mm;
+ int64_t asi_ref_count;
};
DECLARE_PER_CPU_ALIGNED(struct asi_state, asi_cpu_state);
diff --git a/arch/x86/mm/asi.c b/arch/x86/mm/asi.c
index 91e5ff1224ff..ac35323193a3 100644
--- a/arch/x86/mm/asi.c
+++ b/arch/x86/mm/asi.c
@@ -282,9 +282,25 @@ static int __init asi_global_init(void)
}
subsys_initcall(asi_global_init)
+/* We're assuming we hold mm->asi_init_lock */
+static void __asi_destroy(struct asi *asi)
+{
+ if (!boot_cpu_has(X86_FEATURE_ASI))
+ return;
+
+ /* If refcount is non-zero, it means asi_init() was called multiple
+ * times. We free the asi pgd only when the last VM is destroyed. */
+ if (--(asi->asi_ref_count) > 0)
+ return;
+
+ asi_free_pgd(asi);
+ memset(asi, 0, sizeof(struct asi));
+}
+
int asi_init(struct mm_struct *mm, int asi_index, struct asi **out_asi)
{
- struct asi *asi = &mm->asi[asi_index];
+ int err = 0;
+ struct asi *asi = &mm->asi[asi_index];
*out_asi = NULL;
@@ -295,6 +311,15 @@ int asi_init(struct mm_struct *mm, int asi_index, struct asi **out_asi)
WARN_ON(asi_index == 0 || asi_index >= ASI_MAX_NUM);
WARN_ON(asi->pgd != NULL);
+ /* Currently, mm and asi structs are conceptually tied together. In
+ * future implementations an asi object might be unrelated to a specicic
+ * mm. In that future implementation - the mutex will have to be inside
+ * asi. */
+ mutex_lock(&mm->asi_init_lock);
+
+ if (asi->asi_ref_count++ > 0)
+ goto exit_unlock; /* err is 0 */
+
/*
* For now, we allocate 2 pages to avoid any potential problems with
* KPTI code. This won't be needed once KPTI is folded into the ASI
@@ -302,8 +327,10 @@ int asi_init(struct mm_struct *mm, int asi_index, struct asi **out_asi)
*/
asi->pgd = (pgd_t *)__get_free_pages(GFP_PGTABLE_USER,
PGD_ALLOCATION_ORDER);
- if (!asi->pgd)
- return -ENOMEM;
+ if (!asi->pgd) {
+ err = -ENOMEM;
+ goto exit_unlock;
+ }
asi->class = &asi_class[asi_index];
asi->mm = mm;
@@ -328,19 +355,30 @@ int asi_init(struct mm_struct *mm, int asi_index, struct asi **out_asi)
set_pgd(asi->pgd + i, asi_global_nonsensitive_pgd[i]);
}
- *out_asi = asi;
+exit_unlock:
+ if (err)
+ __asi_destroy(asi);
- return 0;
+ /* This unlock signals future asi_init() callers that we finished. */
+ mutex_unlock(&mm->asi_init_lock);
+
+ if (!err)
+ *out_asi = asi;
+ return err;
}
EXPORT_SYMBOL_GPL(asi_init);
void asi_destroy(struct asi *asi)
{
+ struct mm_struct *mm;
+
if (!boot_cpu_has(X86_FEATURE_ASI) || !asi)
return;
- asi_free_pgd(asi);
- memset(asi, 0, sizeof(struct asi));
+ mm = asi->mm;
+ mutex_lock(&mm->asi_init_lock);
+ __asi_destroy(asi);
+ mutex_unlock(&mm->asi_init_lock);
}
EXPORT_SYMBOL_GPL(asi_destroy);
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index f9702d070975..e6980ae31323 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -16,6 +16,7 @@
#include <linux/page-flags-layout.h>
#include <linux/workqueue.h>
#include <linux/seqlock.h>
+#include <linux/mutex.h>
#include <asm/mmu.h>
#include <asm/asi.h>
@@ -628,6 +629,7 @@ struct mm_struct {
* these resources for every mm in the system, we expect that
* only VM mm's will have this flag set. */
bool asi_enabled;
+ struct mutex asi_init_lock;
#endif
struct user_namespace *user_ns;
diff --git a/kernel/fork.c b/kernel/fork.c
index dd5a86e913ea..68b3aeab55ac 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1084,6 +1084,9 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
mm->user_ns = get_user_ns(user_ns);
+#ifdef CONFIG_ADDRESS_SPACE_ISOLATION
+ mutex_init(&mm->asi_init_lock);
+#endif
return mm;
fail_noasi:
--
2.35.1.473.g83b2b277ed-goog
next prev parent reply other threads:[~2022-02-23 5:26 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-23 5:21 [RFC PATCH 00/47] Address Space Isolation for KVM Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 01/47] mm: asi: Introduce ASI core API Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 02/47] mm: asi: Add command-line parameter to enable/disable ASI Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 03/47] mm: asi: Switch to unrestricted address space when entering scheduler Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 04/47] mm: asi: ASI support in interrupts/exceptions Junaid Shahid
2022-03-14 15:50 ` Thomas Gleixner
2022-03-15 2:01 ` Junaid Shahid
2022-03-15 12:55 ` Thomas Gleixner
2022-03-15 22:41 ` Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 05/47] mm: asi: Make __get_current_cr3_fast() ASI-aware Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 06/47] mm: asi: ASI page table allocation and free functions Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 07/47] mm: asi: Functions to map/unmap a memory range into ASI page tables Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 08/47] mm: asi: Add basic infrastructure for global non-sensitive mappings Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 09/47] mm: Add __PAGEFLAG_FALSE Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 10/47] mm: asi: Support for global non-sensitive direct map allocations Junaid Shahid
2022-03-23 21:06 ` Matthew Wilcox
2022-03-23 23:48 ` Junaid Shahid
2022-03-24 1:54 ` Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 11/47] mm: asi: Global non-sensitive vmalloc/vmap support Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 12/47] mm: asi: Support for global non-sensitive slab caches Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 13/47] asi: Added ASI memory cgroup flag Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 14/47] mm: asi: Disable ASI API when ASI is not enabled for a process Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 15/47] kvm: asi: Restricted address space for VM execution Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 16/47] mm: asi: Support for mapping non-sensitive pcpu chunks Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 17/47] mm: asi: Aliased direct map for local non-sensitive allocations Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 18/47] mm: asi: Support for pre-ASI-init " Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 19/47] mm: asi: Support for locally nonsensitive page allocations Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 20/47] mm: asi: Support for locally non-sensitive vmalloc allocations Junaid Shahid
2022-02-23 5:21 ` [RFC PATCH 21/47] mm: asi: Add support for locally non-sensitive VM_USERMAP pages Junaid Shahid
2022-02-23 5:21 ` Junaid Shahid [this message]
2022-02-23 5:21 ` [RFC PATCH 23/47] mm: asi: Add support for mapping all userspace memory into ASI Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 24/47] mm: asi: Support for local non-sensitive slab caches Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 25/47] mm: asi: Avoid warning from NMI userspace accesses in ASI context Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 26/47] mm: asi: Use separate PCIDs for restricted address spaces Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 27/47] mm: asi: Avoid TLB flushes during ASI CR3 switches when possible Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 28/47] mm: asi: Avoid TLB flush IPIs to CPUs not in ASI context Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 29/47] mm: asi: Reduce TLB flushes when freeing pages asynchronously Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 30/47] mm: asi: Add API for mapping userspace address ranges Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 31/47] mm: asi: Support for non-sensitive SLUB caches Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 32/47] x86: asi: Allocate FPU state separately when ASI is enabled Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 33/47] kvm: asi: Map guest memory into restricted ASI address space Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 34/47] kvm: asi: Unmap guest memory from ASI address space when using nested virt Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 35/47] mm: asi: asi_exit() on PF, skip handling if address is accessible Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 36/47] mm: asi: Adding support for dynamic percpu ASI allocations Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 37/47] mm: asi: ASI annotation support for static variables Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 38/47] mm: asi: ASI annotation support for dynamic modules Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 39/47] mm: asi: Skip conventional L1TF/MDS mitigations Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 40/47] mm: asi: support for static percpu DEFINE_PER_CPU*_ASI Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 41/47] mm: asi: Annotation of static variables to be nonsensitive Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 42/47] mm: asi: Annotation of PERCPU " Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 43/47] mm: asi: Annotation of dynamic " Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 44/47] kvm: asi: Splitting kvm_vcpu_arch into non/sensitive parts Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 45/47] mm: asi: Mapping global nonsensitive areas in asi_global_init Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 46/47] kvm: asi: Do asi_exit() in vcpu_run loop before returning to userspace Junaid Shahid
2022-02-23 5:22 ` [RFC PATCH 47/47] mm: asi: Properly un/mapping task stack from ASI + tlb flush Junaid Shahid
2022-03-05 3:39 ` [RFC PATCH 00/47] Address Space Isolation for KVM Hyeonggon Yoo
2022-03-16 21:34 ` Alexandre Chartre
2022-03-17 23:25 ` Junaid Shahid
2022-03-22 9:46 ` Alexandre Chartre
2022-03-23 19:35 ` Junaid Shahid
2022-04-08 8:52 ` Alexandre Chartre
2022-04-11 3:26 ` junaid_shahid
2022-03-16 22:49 ` Thomas Gleixner
2022-03-17 21:24 ` Junaid Shahid
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