Messages in this thread | | | Subject | Re: [RFC PATCH v3 2/7] mm/asi: ASI entry/exit interface | From | Alexandre Chartre <> | Date | Thu, 27 Feb 2020 09:51:29 +0100 |
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On 2/26/20 11:02 PM, Ira Weiny wrote: > On Wed, Feb 26, 2020 at 05:21:55PM +0100, Alexandre Chartre wrote: >> Address Space Isolation (ASI) is entered by calling asi_enter() which >> switches the kernel page-table to the ASI page-table. Isolation is then >> exited by calling asi_exit() which switches the page-table back to the >> original kernel page-table. >> >> The ASI being used and its state is tracked in a per-cpu ASI session >> structure (struct asi_session). >> >> Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com> >> --- >> arch/x86/include/asm/asi.h | 4 ++ >> arch/x86/include/asm/asi_session.h | 17 +++++++ >> arch/x86/include/asm/mmu_context.h | 19 +++++++- >> arch/x86/include/asm/tlbflush.h | 12 +++++ >> arch/x86/mm/asi.c | 90 ++++++++++++++++++++++++++++++++++++ >> 5 files changed, 140 insertions(+), 2 deletions(-) >> create mode 100644 arch/x86/include/asm/asi_session.h >> >> diff --git a/arch/x86/include/asm/asi.h b/arch/x86/include/asm/asi.h >> index 844a81f..29b745a 100644 >> --- a/arch/x86/include/asm/asi.h >> +++ b/arch/x86/include/asm/asi.h >> @@ -44,6 +44,8 @@ >> >> #include <linux/export.h> >> >> +#include <asm/asi_session.h> >> + >> struct asi_type { >> int pcid_prefix; /* PCID prefix */ >> }; >> @@ -80,6 +82,8 @@ struct asi { >> extern struct asi *asi_create(struct asi_type *type); >> extern void asi_destroy(struct asi *asi); >> extern void asi_set_pagetable(struct asi *asi, pgd_t *pagetable); >> +extern int asi_enter(struct asi *asi); >> +extern void asi_exit(struct asi *asi); >> >> #endif /* __ASSEMBLY__ */ >> >> diff --git a/arch/x86/include/asm/asi_session.h b/arch/x86/include/asm/asi_session.h >> new file mode 100644 >> index 0000000..9d39c93 >> --- /dev/null >> +++ b/arch/x86/include/asm/asi_session.h >> @@ -0,0 +1,17 @@ >> +/* SPDX-License-Identifier: GPL-2.0 */ >> +#ifndef ARCH_X86_MM_ASI_SESSION_H >> +#define ARCH_X86_MM_ASI_SESSION_H >> + >> +#ifdef CONFIG_ADDRESS_SPACE_ISOLATION >> + >> +struct asi; >> + >> +struct asi_session { >> + struct asi *asi; /* ASI for this session */ >> + unsigned long isolation_cr3; /* cr3 when ASI is active */ >> + unsigned long original_cr3; /* cr3 before entering ASI */ >> +}; >> + >> +#endif /* CONFIG_ADDRESS_SPACE_ISOLATION */ >> + >> +#endif >> diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h >> index 5f33924..2d65443 100644 >> --- a/arch/x86/include/asm/mmu_context.h >> +++ b/arch/x86/include/asm/mmu_context.h >> @@ -14,6 +14,7 @@ >> #include <asm/paravirt.h> >> #include <asm/mpx.h> >> #include <asm/debugreg.h> >> +#include <asm/asi.h> >> >> extern atomic64_t last_mm_ctx_id; >> >> @@ -349,8 +350,22 @@ static inline bool arch_vma_access_permitted(struct vm_area_struct *vma, >> */ >> static inline unsigned long __get_current_cr3_fast(void) >> { >> - unsigned long cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd, >> - this_cpu_read(cpu_tlbstate.loaded_mm_asid)); >> + unsigned long cr3; >> + >> + /* >> + * If isolation is active then we need to return the CR3 for the >> + * currently active ASI. This value is stored in the isolation_cr3 >> + * field of the ASI session. >> + */ >> + if (IS_ENABLED(CONFIG_ADDRESS_SPACE_ISOLATION) && >> + this_cpu_read(cpu_asi_session.asi)) { >> + cr3 = this_cpu_read(cpu_asi_session.isolation_cr3); >> + /* CR3 read never returns with the NOFLUSH bit */ >> + cr3 &= ~X86_CR3_PCID_NOFLUSH; >> + } else { >> + cr3 = build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd, >> + this_cpu_read(cpu_tlbstate.loaded_mm_asid)); >> + } >> >> /* For now, be very restrictive about when this can be called. */ >> VM_WARN_ON(in_nmi() || preemptible()); >> diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h >> index 6f66d84..241058f 100644 >> --- a/arch/x86/include/asm/tlbflush.h >> +++ b/arch/x86/include/asm/tlbflush.h >> @@ -12,6 +12,7 @@ >> #include <asm/invpcid.h> >> #include <asm/pti.h> >> #include <asm/processor-flags.h> >> +#include <asm/asi.h> >> >> /* >> * The x86 feature is called PCID (Process Context IDentifier). It is similar >> @@ -239,9 +240,20 @@ struct tlb_state { >> * context 0. >> */ >> struct tlb_context ctxs[TLB_NR_DYN_ASIDS]; >> + >> +#ifdef CONFIG_ADDRESS_SPACE_ISOLATION >> + /* >> + * The ASI session tracks the ASI being used and its state. >> + */ >> + struct asi_session asi_session; >> +#endif >> }; >> DECLARE_PER_CPU_SHARED_ALIGNED(struct tlb_state, cpu_tlbstate); >> >> +#ifdef CONFIG_ADDRESS_SPACE_ISOLATION >> +#define cpu_asi_session (cpu_tlbstate.asi_session) >> +#endif >> + >> /* >> * Blindly accessing user memory from NMI context can be dangerous >> * if we're in the middle of switching the current user task or >> diff --git a/arch/x86/mm/asi.c b/arch/x86/mm/asi.c >> index 0a0ac9d..9fbc921 100644 >> --- a/arch/x86/mm/asi.c >> +++ b/arch/x86/mm/asi.c >> @@ -10,6 +10,8 @@ >> >> #include <asm/asi.h> >> #include <asm/bug.h> >> +#include <asm/mmu_context.h> >> +#include <asm/tlbflush.h> >> >> struct asi *asi_create(struct asi_type *type) >> { >> @@ -58,3 +60,91 @@ void asi_set_pagetable(struct asi *asi, pgd_t *pagetable) >> >> } >> EXPORT_SYMBOL(asi_set_pagetable); >> + >> +static void asi_switch_to_asi_cr3(struct asi *asi) >> +{ >> + unsigned long original_cr3, asi_cr3; >> + struct asi_session *asi_session; >> + u16 pcid; >> + >> + WARN_ON(!irqs_disabled()); >> + >> + original_cr3 = __get_current_cr3_fast(); >> + >> + /* build the ASI cr3 value */ >> + asi_cr3 = asi->base_cr3; >> + if (boot_cpu_has(X86_FEATURE_PCID)) { >> + pcid = original_cr3 & ASI_KERNEL_PCID_MASK; >> + asi_cr3 |= pcid; >> + } >> + >> + /* get the ASI session ready for entering ASI */ >> + asi_session = &get_cpu_var(cpu_asi_session); >> + asi_session->asi = asi; >> + asi_session->original_cr3 = original_cr3; >> + asi_session->isolation_cr3 = asi_cr3; >> + >> + /* Update CR3 to immediately enter ASI */ >> + native_write_cr3(asi_cr3); >> +} >> + >> +static void asi_switch_to_kernel_cr3(struct asi *asi) > > asi is not used in this function? >
You are right, I was probably using it in a previous version of the code and forgot to remote it. I will remove it.
>> +{ >> + struct asi_session *asi_session; >> + unsigned long original_cr3; >> + >> + WARN_ON(!irqs_disabled()); >> + >> + original_cr3 = this_cpu_read(cpu_asi_session.original_cr3); >> + if (boot_cpu_has(X86_FEATURE_PCID)) >> + original_cr3 |= X86_CR3_PCID_NOFLUSH; >> + native_write_cr3(original_cr3); >> + >> + asi_session = &get_cpu_var(cpu_asi_session); >> + asi_session->asi = NULL; >> +} >> + >> +int asi_enter(struct asi *asi) >> +{ >> + struct asi *current_asi; >> + unsigned long flags; >> + >> + /* >> + * We can re-enter isolation, but only with the same ASI (we don't >> + * support nesting isolation). >> + */ >> + current_asi = this_cpu_read(cpu_asi_session.asi); >> + if (current_asi) { >> + if (current_asi != asi) { >> + WARN_ON(1); >> + return -EBUSY; >> + } > > if (WARN_ON(current_asi != asi)) { > return -EBUSY; >
Yes, much better, will change.
Thanks,
alex.
> >> + return 0; >> + } >> + >> + local_irq_save(flags); >> + asi_switch_to_asi_cr3(asi); >> + local_irq_restore(flags); >> + >> + return 0; >> +} >> +EXPORT_SYMBOL(asi_enter); >> + >> +void asi_exit(struct asi *asi) >> +{ >> + struct asi *current_asi; >> + unsigned long flags; >> + >> + current_asi = this_cpu_read(cpu_asi_session.asi); >> + if (!current_asi) { >> + /* already exited */ >> + return; >> + } >> + >> + WARN_ON(current_asi != asi); >> + >> + local_irq_save(flags); >> + asi_switch_to_kernel_cr3(asi); >> + local_irq_restore(flags); >> +} >> +EXPORT_SYMBOL(asi_exit); >> -- >> 1.7.1 >> >> >
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