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Message-ID: <20250302123838.GKZ8RRTgRxvBSry6mk@fat_crate.local>
Date: Sun, 2 Mar 2025 13:38:38 +0100
From: Borislav Petkov <bp@...en8.de>
To: Rik van Riel <riel@...riel.com>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, peterz@...radead.org,
dave.hansen@...ux.intel.com, zhengqi.arch@...edance.com,
nadav.amit@...il.com, thomas.lendacky@....com, kernel-team@...a.com,
linux-mm@...ck.org, akpm@...ux-foundation.org, jackmanb@...gle.com,
jannh@...gle.com, mhklinux@...look.com, andrew.cooper3@...rix.com,
Manali.Shukla@....com, mingo@...nel.org
Subject: Re: [PATCH v14 09/13] x86/mm: global ASID process exit helpers
On Tue, Feb 25, 2025 at 10:00:44PM -0500, Rik van Riel wrote:
> A global ASID is allocated for the lifetime of a process.
>
> Free the global ASID at process exit time.
>
> Signed-off-by: Rik van Riel <riel@...riel.com>
> ---
> arch/x86/include/asm/mmu_context.h | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
So I don't like the ifdeffery and tried removing it, see below.
So I added helpers.
Then I entered the include hell.
And then I caught a bug with the DISABLED_FEATURE stuff.
Anyway, see below. It builds the allno-, defconfig and mine I use on this
machine so more testing is definitely needed. But the end result looks a lot
better now.
I'll integrate the other changes into the respective patches and I probably
should push my branch somewhere as we have accumulated a lot of changes by now
so tracking them over mail is getting not that easy anymore.
Will do so on Monday.
diff --git a/arch/x86/Kconfig.cpufeatures b/arch/x86/Kconfig.cpufeatures
index f9af51205f07..3207e5546438 100644
--- a/arch/x86/Kconfig.cpufeatures
+++ b/arch/x86/Kconfig.cpufeatures
@@ -196,6 +196,6 @@ config X86_DISABLED_FEATURE_SEV_SNP
def_bool y
depends on !KVM_AMD_SEV
-config X86_DISABLED_FEATURE_BROADCAST_TLB_FLUSH
+config X86_DISABLED_FEATURE_INVLPGB
def_bool y
depends on !X86_BROADCAST_TLB_FLUSH
diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index a2c70e495b1b..2398058b6e83 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -2,7 +2,6 @@
#ifndef _ASM_X86_MMU_CONTEXT_H
#define _ASM_X86_MMU_CONTEXT_H
-#include <asm/desc.h>
#include <linux/atomic.h>
#include <linux/mm_types.h>
#include <linux/pkeys.h>
@@ -13,6 +12,7 @@
#include <asm/paravirt.h>
#include <asm/debugreg.h>
#include <asm/gsseg.h>
+#include <asm/desc.h>
extern atomic64_t last_mm_ctx_id;
@@ -139,6 +139,9 @@ static inline void mm_reset_untag_mask(struct mm_struct *mm)
#define enter_lazy_tlb enter_lazy_tlb
extern void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk);
+#define mm_init_global_asid mm_init_global_asid
+extern void mm_init_global_asid(struct mm_struct *mm);
+
extern void mm_free_global_asid(struct mm_struct *mm);
/*
@@ -163,6 +166,8 @@ static inline int init_new_context(struct task_struct *tsk,
mm->context.execute_only_pkey = -1;
}
#endif
+
+ mm_init_global_asid(mm);
mm_reset_untag_mask(mm);
init_new_context_ldt(mm);
return 0;
@@ -172,6 +177,7 @@ static inline int init_new_context(struct task_struct *tsk,
static inline void destroy_context(struct mm_struct *mm)
{
destroy_context_ldt(mm);
+ mm_free_global_asid(mm);
}
extern void switch_mm(struct mm_struct *prev, struct mm_struct *next,
diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 37b735dcf025..01d8a152f04a 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -261,6 +261,14 @@ static inline u16 mm_global_asid(struct mm_struct *mm)
return asid;
}
+static inline void mm_init_global_asid(struct mm_struct *mm)
+{
+ if (cpu_feature_enabled(X86_FEATURE_INVLPGB)) {
+ mm->context.global_asid = 0;
+ mm->context.asid_transition = false;
+ }
+}
+
static inline void mm_assign_global_asid(struct mm_struct *mm, u16 asid)
{
/*
@@ -272,7 +280,7 @@ static inline void mm_assign_global_asid(struct mm_struct *mm, u16 asid)
smp_store_release(&mm->context.global_asid, asid);
}
-static inline bool in_asid_transition(struct mm_struct *mm)
+static inline bool mm_in_asid_transition(struct mm_struct *mm)
{
if (!cpu_feature_enabled(X86_FEATURE_INVLPGB))
return false;
@@ -280,19 +288,10 @@ static inline bool in_asid_transition(struct mm_struct *mm)
return mm && READ_ONCE(mm->context.asid_transition);
}
#else
-static inline u16 mm_global_asid(struct mm_struct *mm)
-{
- return 0;
-}
-
-static inline void mm_assign_global_asid(struct mm_struct *mm, u16 asid)
-{
-}
-
-static inline bool in_asid_transition(struct mm_struct *mm)
-{
- return false;
-}
+static inline u16 mm_global_asid(struct mm_struct *mm) { return 0; }
+static inline void mm_init_global_asid(struct mm_struct *mm) { }
+static inline void mm_assign_global_asid(struct mm_struct *mm, u16 asid) { }
+static inline bool mm_in_asid_transition(struct mm_struct *mm) { return false; }
#endif
#ifdef CONFIG_PARAVIRT
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index cb43ab08ea4a..c2167b331bbe 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -396,6 +396,9 @@ static void use_global_asid(struct mm_struct *mm)
void mm_free_global_asid(struct mm_struct *mm)
{
+ if (!cpu_feature_enabled(X86_FEATURE_INVLPGB))
+ return;
+
if (!mm_global_asid(mm))
return;
@@ -1161,7 +1164,7 @@ STATIC_NOPV void native_flush_tlb_multi(const struct cpumask *cpumask,
* up on the new contents of what used to be page tables, while
* doing a speculative memory access.
*/
- if (info->freed_tables || in_asid_transition(info->mm))
+ if (info->freed_tables || mm_in_asid_transition(info->mm))
on_each_cpu_mask(cpumask, flush_tlb_func, (void *)info, true);
else
on_each_cpu_cond_mask(should_flush_tlb, flush_tlb_func,
--
2.43.0
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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