This is a note to let you know that I've just added the patch titled

kaiser: enhanced by kernel and user PCIDs

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: kaiser-enhanced-by-kernel-and-user-pcids.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Wed Jan 3 18:58:12 CET 2018

From: Dave Hansen dave.hansen@linux.intel.com Date: Wed, 30 Aug 2017 16:23:00 -0700 Subject: kaiser: enhanced by kernel and user PCIDs

From: Dave Hansen dave.hansen@linux.intel.com

Merged performance improvements to Kaiser, using distinct kernel and user Process Context Identifiers to minimize the TLB flushing.

Signed-off-by: Hugh Dickins hughd@google.com Acked-by: Jiri Kosina jkosina@suse.cz Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/entry/entry_64.S | 10 ++++- arch/x86/entry/entry_64_compat.S | 1 arch/x86/include/asm/cpufeature.h | 1 arch/x86/include/asm/kaiser.h | 15 ++++++- arch/x86/include/asm/pgtable_types.h | 26 +++++++++++++ arch/x86/include/asm/tlbflush.h | 54 +++++++++++++++++++++++----- arch/x86/include/uapi/asm/processor-flags.h | 3 + arch/x86/kernel/cpu/common.c | 34 +++++++++++++++++ arch/x86/kvm/x86.c | 3 + arch/x86/mm/kaiser.c | 7 +++ arch/x86/mm/tlb.c | 46 ++++++++++++++++++++++- 11 files changed, 182 insertions(+), 18 deletions(-)

--- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1291,7 +1291,10 @@ ENTRY(nmi) /* %rax is saved above, so OK to clobber here */ movq %cr3, %rax pushq %rax - andq $(~KAISER_SHADOW_PGD_OFFSET), %rax + /* mask off "user" bit of pgd address and 12 PCID bits: */ + andq $(~(X86_CR3_PCID_ASID_MASK | KAISER_SHADOW_PGD_OFFSET)), %rax + /* Add back kernel PCID and "no flush" bit */ + orq X86_CR3_PCID_KERN_VAR, %rax movq %rax, %cr3 #endif call do_nmi @@ -1532,7 +1535,10 @@ end_repeat_nmi: /* %rax is saved above, so OK to clobber here */ movq %cr3, %rax pushq %rax - andq $(~KAISER_SHADOW_PGD_OFFSET), %rax + /* mask off "user" bit of pgd address and 12 PCID bits: */ + andq $(~(X86_CR3_PCID_ASID_MASK | KAISER_SHADOW_PGD_OFFSET)), %rax + /* Add back kernel PCID and "no flush" bit */ + orq X86_CR3_PCID_KERN_VAR, %rax movq %rax, %cr3 #endif

--- a/arch/x86/entry/entry_64_compat.S +++ b/arch/x86/entry/entry_64_compat.S @@ -13,6 +13,7 @@ #include <asm/irqflags.h> #include <asm/asm.h> #include <asm/smap.h> +#include <asm/pgtable_types.h> #include <asm/kaiser.h> #include <linux/linkage.h> #include <linux/err.h> --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -187,6 +187,7 @@ #define X86_FEATURE_ARAT ( 7*32+ 1) /* Always Running APIC Timer */ #define X86_FEATURE_CPB ( 7*32+ 2) /* AMD Core Performance Boost */ #define X86_FEATURE_EPB ( 7*32+ 3) /* IA32_ENERGY_PERF_BIAS support */ +#define X86_FEATURE_INVPCID_SINGLE ( 7*32+ 4) /* Effectively INVPCID && CR4.PCIDE=1 */ #define X86_FEATURE_PLN ( 7*32+ 5) /* Intel Power Limit Notification */ #define X86_FEATURE_PTS ( 7*32+ 6) /* Intel Package Thermal Status */ #define X86_FEATURE_DTHERM ( 7*32+ 7) /* Digital Thermal Sensor */ --- a/arch/x86/include/asm/kaiser.h +++ b/arch/x86/include/asm/kaiser.h @@ -1,5 +1,8 @@ #ifndef _ASM_X86_KAISER_H #define _ASM_X86_KAISER_H + +#include <uapi/asm/processor-flags.h> /* For PCID constants */ + /* * This file includes the definitions for the KAISER feature. * KAISER is a counter measure against x86_64 side channel attacks on @@ -21,13 +24,21 @@

.macro _SWITCH_TO_KERNEL_CR3 reg movq %cr3, \reg -andq $(~KAISER_SHADOW_PGD_OFFSET), \reg +andq $(~(X86_CR3_PCID_ASID_MASK | KAISER_SHADOW_PGD_OFFSET)), \reg +orq X86_CR3_PCID_KERN_VAR, \reg movq \reg, %cr3 .endm

.macro _SWITCH_TO_USER_CR3 reg movq %cr3, \reg -orq $(KAISER_SHADOW_PGD_OFFSET), \reg +andq $(~(X86_CR3_PCID_ASID_MASK | KAISER_SHADOW_PGD_OFFSET)), \reg +/* + * This can obviously be one instruction by putting the + * KAISER_SHADOW_PGD_OFFSET bit in the X86_CR3_PCID_USER_VAR. + * But, just leave it now for simplicity. + */ +orq X86_CR3_PCID_USER_VAR, \reg +orq $(KAISER_SHADOW_PGD_OFFSET), \reg movq \reg, %cr3 .endm

--- a/arch/x86/include/asm/pgtable_types.h +++ b/arch/x86/include/asm/pgtable_types.h @@ -106,6 +106,32 @@ _PAGE_SOFT_DIRTY) #define _HPAGE_CHG_MASK (_PAGE_CHG_MASK | _PAGE_PSE)

+/* The ASID is the lower 12 bits of CR3 */ +#define X86_CR3_PCID_ASID_MASK (_AC((1<<12)-1,UL)) + +/* Mask for all the PCID-related bits in CR3: */ +#define X86_CR3_PCID_MASK (X86_CR3_PCID_NOFLUSH | X86_CR3_PCID_ASID_MASK) +#if defined(CONFIG_KAISER) && defined(CONFIG_X86_64) +#define X86_CR3_PCID_ASID_KERN (_AC(0x4,UL)) +#define X86_CR3_PCID_ASID_USER (_AC(0x6,UL)) + +#define X86_CR3_PCID_KERN_FLUSH (X86_CR3_PCID_ASID_KERN) +#define X86_CR3_PCID_USER_FLUSH (X86_CR3_PCID_ASID_USER) +#define X86_CR3_PCID_KERN_NOFLUSH (X86_CR3_PCID_NOFLUSH | X86_CR3_PCID_ASID_KERN) +#define X86_CR3_PCID_USER_NOFLUSH (X86_CR3_PCID_NOFLUSH | X86_CR3_PCID_ASID_USER) +#else +#define X86_CR3_PCID_ASID_KERN (_AC(0x0,UL)) +#define X86_CR3_PCID_ASID_USER (_AC(0x0,UL)) +/* + * PCIDs are unsupported on 32-bit and none of these bits can be + * set in CR3: + */ +#define X86_CR3_PCID_KERN_FLUSH (0) +#define X86_CR3_PCID_USER_FLUSH (0) +#define X86_CR3_PCID_KERN_NOFLUSH (0) +#define X86_CR3_PCID_USER_NOFLUSH (0) +#endif + /* * The cache modes defined here are used to translate between pure SW usage * and the HW defined cache mode bits and/or PAT entries. --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -12,7 +12,6 @@ static inline void __invpcid(unsigned lo unsigned long type) { struct { u64 d[2]; } desc = { { pcid, addr } }; - /* * The memory clobber is because the whole point is to invalidate * stale TLB entries and, especially if we're flushing global @@ -133,14 +132,25 @@ static inline void cr4_set_bits_and_upda

static inline void __native_flush_tlb(void) { + if (!cpu_feature_enabled(X86_FEATURE_INVPCID)) { + /* + * If current->mm == NULL then we borrow a mm which may change during a + * task switch and therefore we must not be preempted while we write CR3 + * back: + */ + preempt_disable(); + native_write_cr3(native_read_cr3()); + preempt_enable(); + return; + } /* - * If current->mm == NULL then we borrow a mm which may change during a - * task switch and therefore we must not be preempted while we write CR3 - * back: - */ - preempt_disable(); - native_write_cr3(native_read_cr3()); - preempt_enable(); + * We are no longer using globals with KAISER, so a + * "nonglobals" flush would work too. But, this is more + * conservative. + * + * Note, this works with CR4.PCIDE=0 or 1. + */ + invpcid_flush_all(); }

static inline void __native_flush_tlb_global_irq_disabled(void) @@ -162,6 +172,8 @@ static inline void __native_flush_tlb_gl /* * Using INVPCID is considerably faster than a pair of writes * to CR4 sandwiched inside an IRQ flag save/restore. + * + * Note, this works with CR4.PCIDE=0 or 1. */ invpcid_flush_all(); return; @@ -181,7 +193,31 @@ static inline void __native_flush_tlb_gl

static inline void __native_flush_tlb_single(unsigned long addr) { - asm volatile("invlpg (%0)" ::"r" (addr) : "memory"); + /* + * SIMICS #GP's if you run INVPCID with type 2/3 + * and X86_CR4_PCIDE clear. Shame! + * + * The ASIDs used below are hard-coded. But, we must not + * call invpcid(type=1/2) before CR4.PCIDE=1. Just call + * invpcid in the case we are called early. + */ + if (!this_cpu_has(X86_FEATURE_INVPCID_SINGLE)) { + asm volatile("invlpg (%0)" ::"r" (addr) : "memory"); + return; + } + /* Flush the address out of both PCIDs. */ + /* + * An optimization here might be to determine addresses + * that are only kernel-mapped and only flush the kernel + * ASID. But, userspace flushes are probably much more + * important performance-wise. + * + * Make sure to do only a single invpcid when KAISER is + * disabled and we have only a single ASID. + */ + if (X86_CR3_PCID_ASID_KERN != X86_CR3_PCID_ASID_USER) + invpcid_flush_one(X86_CR3_PCID_ASID_KERN, addr); + invpcid_flush_one(X86_CR3_PCID_ASID_USER, addr); }

static inline void __flush_tlb_all(void) --- a/arch/x86/include/uapi/asm/processor-flags.h +++ b/arch/x86/include/uapi/asm/processor-flags.h @@ -77,7 +77,8 @@ #define X86_CR3_PWT _BITUL(X86_CR3_PWT_BIT) #define X86_CR3_PCD_BIT 4 /* Page Cache Disable */ #define X86_CR3_PCD _BITUL(X86_CR3_PCD_BIT) -#define X86_CR3_PCID_MASK _AC(0x00000fff,UL) /* PCID Mask */ +#define X86_CR3_PCID_NOFLUSH_BIT 63 /* Preserve old PCID */ +#define X86_CR3_PCID_NOFLUSH _BITULL(X86_CR3_PCID_NOFLUSH_BIT)

/* * Intel CPU features in CR4 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -321,11 +321,45 @@ static __always_inline void setup_smap(s } }

+/* + * These can have bit 63 set, so we can not just use a plain "or" + * instruction to get their value or'd into CR3. It would take + * another register. So, we use a memory reference to these + * instead. + * + * This is also handy because systems that do not support + * PCIDs just end up or'ing a 0 into their CR3, which does + * no harm. + */ +__aligned(PAGE_SIZE) unsigned long X86_CR3_PCID_KERN_VAR = 0; +__aligned(PAGE_SIZE) unsigned long X86_CR3_PCID_USER_VAR = 0; + static void setup_pcid(struct cpuinfo_x86 *c) { if (cpu_has(c, X86_FEATURE_PCID)) { if (cpu_has(c, X86_FEATURE_PGE)) { cr4_set_bits(X86_CR4_PCIDE); + /* + * These variables are used by the entry/exit + * code to change PCIDs. + */ +#ifdef CONFIG_KAISER + X86_CR3_PCID_KERN_VAR = X86_CR3_PCID_KERN_NOFLUSH; + X86_CR3_PCID_USER_VAR = X86_CR3_PCID_USER_NOFLUSH; +#endif + /* + * INVPCID has two "groups" of types: + * 1/2: Invalidate an individual address + * 3/4: Invalidate all contexts + * + * 1/2 take a PCID, but 3/4 do not. So, 3/4 + * ignore the PCID argument in the descriptor. + * But, we have to be careful not to call 1/2 + * with an actual non-zero PCID in them before + * we do the above cr4_set_bits(). + */ + if (cpu_has(c, X86_FEATURE_INVPCID)) + set_cpu_cap(c, X86_FEATURE_INVPCID_SINGLE); } else { /* * flush_tlb_all(), as currently implemented, won't --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -759,7 +759,8 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, u return 1;

/* PCID can not be enabled when cr3[11:0]!=000H or EFER.LMA=0 */ - if ((kvm_read_cr3(vcpu) & X86_CR3_PCID_MASK) || !is_long_mode(vcpu)) + if ((kvm_read_cr3(vcpu) & X86_CR3_PCID_ASID_MASK) || + !is_long_mode(vcpu)) return 1; }

--- a/arch/x86/mm/kaiser.c +++ b/arch/x86/mm/kaiser.c @@ -240,6 +240,8 @@ static void __init kaiser_init_all_pgds( } while (0)

extern char __per_cpu_user_mapped_start[], __per_cpu_user_mapped_end[]; +extern unsigned long X86_CR3_PCID_KERN_VAR; +extern unsigned long X86_CR3_PCID_USER_VAR; /* * If anything in here fails, we will likely die on one of the * first kernel->user transitions and init will die. But, we @@ -290,6 +292,11 @@ void __init kaiser_init(void) kaiser_add_user_map_early(&debug_idt_table, sizeof(gate_desc) * NR_VECTORS, __PAGE_KERNEL); + + kaiser_add_user_map_early(&X86_CR3_PCID_KERN_VAR, PAGE_SIZE, + __PAGE_KERNEL); + kaiser_add_user_map_early(&X86_CR3_PCID_USER_VAR, PAGE_SIZE, + __PAGE_KERNEL); }

/* Add a mapping to the shadow mapping, and synchronize the mappings */ --- a/arch/x86/mm/tlb.c +++ b/arch/x86/mm/tlb.c @@ -34,6 +34,46 @@ struct flush_tlb_info { unsigned long flush_end; };

+static void load_new_mm_cr3(pgd_t *pgdir) +{ + unsigned long new_mm_cr3 = __pa(pgdir); + + /* + * KAISER, plus PCIDs needs some extra work here. But, + * if either of features is not present, we need no + * PCIDs here and just do a normal, full TLB flush with + * the write_cr3() + */ + if (!IS_ENABLED(CONFIG_KAISER) || + !cpu_feature_enabled(X86_FEATURE_PCID)) + goto out_set_cr3; + /* + * We reuse the same PCID for different tasks, so we must + * flush all the entires for the PCID out when we change + * tasks. + */ + new_mm_cr3 = X86_CR3_PCID_KERN_FLUSH | __pa(pgdir); + + /* + * The flush from load_cr3() may leave old TLB entries + * for userspace in place. We must flush that context + * separately. We can theoretically delay doing this + * until we actually load up the userspace CR3, but + * that's a bit tricky. We have to have the "need to + * flush userspace PCID" bit per-cpu and check it in the + * exit-to-userspace paths. + */ + invpcid_flush_single_context(X86_CR3_PCID_ASID_USER); + +out_set_cr3: + /* + * Caution: many callers of this function expect + * that load_cr3() is serializing and orders TLB + * fills with respect to the mm_cpumask writes. + */ + write_cr3(new_mm_cr3); +} + /* * We cannot call mmdrop() because we are in interrupt context, * instead update mm->cpu_vm_mask. @@ -45,7 +85,7 @@ void leave_mm(int cpu) BUG(); if (cpumask_test_cpu(cpu, mm_cpumask(active_mm))) { cpumask_clear_cpu(cpu, mm_cpumask(active_mm)); - load_cr3(swapper_pg_dir); + load_new_mm_cr3(swapper_pg_dir); /* * This gets called in the idle path where RCU * functions differently. Tracing normally @@ -105,7 +145,7 @@ void switch_mm_irqs_off(struct mm_struct * ordering guarantee we need. * */ - load_cr3(next->pgd); + load_new_mm_cr3(next->pgd);

trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL);

@@ -152,7 +192,7 @@ void switch_mm_irqs_off(struct mm_struct * As above, load_cr3() is serializing and orders TLB * fills with respect to the mm_cpumask write. */ - load_cr3(next->pgd); + load_new_mm_cr3(next->pgd); trace_tlb_flush(TLB_FLUSH_ON_TASK_SWITCH, TLB_FLUSH_ALL); load_mm_cr4(next); load_mm_ldt(next);

Patches currently in stable-queue which might be from dave.hansen@linux.intel.com are

queue-4.4/x86-paravirt-dont-patch-flush_tlb_single.patch queue-4.4/kaiser-merged-update.patch queue-4.4/kaiser-enhanced-by-kernel-and-user-pcids.patch