x86/mm: Make MMU_GATHER_RCU_TABLE_FREE unconditional

[ Upstream commit a37259732a7dc33047fa1e4f9a338088f452e017 ]

Currently x86 uses CONFIG_MMU_GATHER_TABLE_FREE when using
paravirt, and not when running on bare metal.

There is no real good reason to do things differently for
each setup. Make them all the same.

Currently get_user_pages_fast synchronizes against page table
freeing in two different ways:

 - on bare metal, by blocking IRQs, which block TLB flush IPIs
 - on paravirt, with MMU_GATHER_RCU_TABLE_FREE

This is done because some paravirt TLB flush implementations
handle the TLB flush in the hypervisor, and will do the flush
even when the target CPU has interrupts disabled.

Always handle page table freeing with MMU_GATHER_RCU_TABLE_FREE.
Using RCU synchronization between page table freeing and get_user_pages_fast()
allows bare metal to also do TLB flushing while interrupts are disabled.

Various places in the mm do still block IRQs or disable preemption
as an implicit way to block RCU frees.

That makes it safe to use INVLPGB on AMD CPUs.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Manali Shukla <Manali.Shukla@amd.com>
Tested-by: Brendan Jackman <jackmanb@google.com>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Link: https://lore.kernel.org/r/20250213161423.449435-2-riel@surriel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f86e7072a5ba3b022fec57dc9b43e1a98f000a7c..473364353bd9646ff173667e29c513067f353b9b 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -277,7 +277,7 @@ config X86
        select HAVE_PCI
        select HAVE_PERF_REGS
        select HAVE_PERF_USER_STACK_DUMP
-       select MMU_GATHER_RCU_TABLE_FREE        if PARAVIRT
+       select MMU_GATHER_RCU_TABLE_FREE
        select MMU_GATHER_MERGE_VMAS
        select HAVE_POSIX_CPU_TIMERS_TASK_WORK
        select HAVE_REGS_AND_STACK_ACCESS_API

diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index c5bb980b8a6732043dcd6ab22ff7f7037643431d..6669d251c4f75d5589f46cd3be9e5edc1335c4fb 100644 (file)
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -59,21 +59,6 @@ void __init native_pv_lock_init(void)
                static_branch_enable(&virt_spin_lock_key);
 }
 
-#ifndef CONFIG_PT_RECLAIM
-static void native_tlb_remove_table(struct mmu_gather *tlb, void *table)
-{
-       struct ptdesc *ptdesc = (struct ptdesc *)table;
-
-       pagetable_dtor(ptdesc);
-       tlb_remove_page(tlb, ptdesc_page(ptdesc));
-}
-#else
-static void native_tlb_remove_table(struct mmu_gather *tlb, void *table)
-{
-       tlb_remove_table(tlb, table);
-}
-#endif
-
 struct static_key paravirt_steal_enabled;
 struct static_key paravirt_steal_rq_enabled;
 
@@ -197,7 +182,7 @@ struct paravirt_patch_template pv_ops = {
        .mmu.flush_tlb_kernel   = native_flush_tlb_global,
        .mmu.flush_tlb_one_user = native_flush_tlb_one_user,
        .mmu.flush_tlb_multi    = native_flush_tlb_multi,
-       .mmu.tlb_remove_table   = native_tlb_remove_table,
+       .mmu.tlb_remove_table   = tlb_remove_table,
 
        .mmu.exit_mmap          = paravirt_nop,
        .mmu.notify_page_enc_status_changed     = paravirt_nop,

diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 9b0ee41b545c7ec766274f00c8ccb5c3dcc3e108..1ddbd799acdf5e8fe985ec15782817d475ecdd79 100644 (file)
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -18,25 +18,6 @@ EXPORT_SYMBOL(physical_mask);
 #define PGTABLE_HIGHMEM 0
 #endif
 
-#ifndef CONFIG_PARAVIRT
-#ifndef CONFIG_PT_RECLAIM
-static inline
-void paravirt_tlb_remove_table(struct mmu_gather *tlb, void *table)
-{
-       struct ptdesc *ptdesc = (struct ptdesc *)table;
-
-       pagetable_dtor(ptdesc);
-       tlb_remove_page(tlb, ptdesc_page(ptdesc));
-}
-#else
-static inline
-void paravirt_tlb_remove_table(struct mmu_gather *tlb, void *table)
-{
-       tlb_remove_table(tlb, table);
-}
-#endif /* !CONFIG_PT_RECLAIM */
-#endif /* !CONFIG_PARAVIRT */
-
 gfp_t __userpte_alloc_gfp = GFP_PGTABLE_USER | PGTABLE_HIGHMEM;
 
 pgtable_t pte_alloc_one(struct mm_struct *mm)
@@ -64,7 +45,7 @@ early_param("userpte", setup_userpte);
 void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte)
 {
        paravirt_release_pte(page_to_pfn(pte));
-       paravirt_tlb_remove_table(tlb, page_ptdesc(pte));
+       tlb_remove_table(tlb, page_ptdesc(pte));
 }
 
 #if CONFIG_PGTABLE_LEVELS > 2
@@ -78,21 +59,21 @@ void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd)
 #ifdef CONFIG_X86_PAE
        tlb->need_flush_all = 1;
 #endif
-       paravirt_tlb_remove_table(tlb, virt_to_ptdesc(pmd));
+       tlb_remove_table(tlb, virt_to_ptdesc(pmd));
 }
 
 #if CONFIG_PGTABLE_LEVELS > 3
 void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud)
 {
        paravirt_release_pud(__pa(pud) >> PAGE_SHIFT);
-       paravirt_tlb_remove_table(tlb, virt_to_ptdesc(pud));
+       tlb_remove_table(tlb, virt_to_ptdesc(pud));
 }
 
 #if CONFIG_PGTABLE_LEVELS > 4
 void ___p4d_free_tlb(struct mmu_gather *tlb, p4d_t *p4d)
 {
        paravirt_release_p4d(__pa(p4d) >> PAGE_SHIFT);
-       paravirt_tlb_remove_table(tlb, virt_to_ptdesc(p4d));
+       tlb_remove_table(tlb, virt_to_ptdesc(p4d));
 }
 #endif /* CONFIG_PGTABLE_LEVELS > 4 */
 #endif /* CONFIG_PGTABLE_LEVELS > 3 */