From 8ef46a672a7d852709561d10672b6eaa8a4acd82 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Thu, 5 Mar 2015 19:19:02 -0800 Subject: x86/asm/entry: Add this_cpu_sp0() to read sp0 for the current cpu We currently store references to the top of the kernel stack in multiple places: kernel_stack (with an offset) and init_tss.x86_tss.sp0 (no offset). The latter is defined by hardware and is a clean canonical way to find the top of the stack. Add an accessor so we can start using it. This needs minor paravirt tweaks. On native, sp0 defines the top of the kernel stack and is therefore always correct. On Xen and lguest, the hypervisor tracks the top of the stack, but we want to start reading sp0 in the kernel. Fixing this is simple: just update our local copy of sp0 as well as the hypervisor's copy on task switches. Signed-off-by: Andy Lutomirski Cc: Boris Ostrovsky Cc: Borislav Petkov Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Konrad Rzeszutek Wilk Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Rusty Russell Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/8d675581859712bee09a055ed8f785d80dac1eca.1425611534.git.luto@amacapital.net Signed-off-by: Ingo Molnar --- arch/x86/xen/enlighten.c | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/xen') diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index 5240f563076d..81665c9f2132 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -912,6 +912,7 @@ static void xen_load_sp0(struct tss_struct *tss, mcs = xen_mc_entry(0); MULTI_stack_switch(mcs.mc, __KERNEL_DS, thread->sp0); xen_mc_issue(PARAVIRT_LAZY_CPU); + tss->x86_tss.sp0 = thread->sp0; } static void xen_set_iopl_mask(unsigned mask) -- cgit v1.2.2 From c38e503804b0402c510f82437069f7769fa0cea9 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Tue, 17 Mar 2015 14:42:59 +0100 Subject: x86/asm/entry/64: Rename 'old_rsp' to 'rsp_scratch' Make clear that the usage of PER_CPU(old_rsp) is purely temporary, by renaming it to 'rsp_scratch'. Cc: Alexei Starovoitov Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Denys Vlasenko Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Steven Rostedt Cc: Will Drewry Signed-off-by: Ingo Molnar --- arch/x86/xen/xen-asm_64.S | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'arch/x86/xen') diff --git a/arch/x86/xen/xen-asm_64.S b/arch/x86/xen/xen-asm_64.S index 53adefda4275..985fc3ee0973 100644 --- a/arch/x86/xen/xen-asm_64.S +++ b/arch/x86/xen/xen-asm_64.S @@ -68,11 +68,11 @@ ENTRY(xen_sysret64) * We're already on the usermode stack at this point, but * still with the kernel gs, so we can easily switch back */ - movq %rsp, PER_CPU_VAR(old_rsp) + movq %rsp, PER_CPU_VAR(rsp_scratch) movq PER_CPU_VAR(kernel_stack), %rsp pushq $__USER_DS - pushq PER_CPU_VAR(old_rsp) + pushq PER_CPU_VAR(rsp_scratch) pushq %r11 pushq $__USER_CS pushq %rcx @@ -87,11 +87,11 @@ ENTRY(xen_sysret32) * We're already on the usermode stack at this point, but * still with the kernel gs, so we can easily switch back */ - movq %rsp, PER_CPU_VAR(old_rsp) + movq %rsp, PER_CPU_VAR(rsp_scratch) movq PER_CPU_VAR(kernel_stack), %rsp pushq $__USER32_DS - pushq PER_CPU_VAR(old_rsp) + pushq PER_CPU_VAR(rsp_scratch) pushq %r11 pushq $__USER32_CS pushq %rcx -- cgit v1.2.2 From ef593260f0cae2699874f098fb5b19fb46502cb3 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Thu, 19 Mar 2015 18:17:46 +0100 Subject: x86/asm/entry: Get rid of KERNEL_STACK_OFFSET PER_CPU_VAR(kernel_stack) was set up in a way where it points five stack slots below the top of stack. Presumably, it was done to avoid one "sub $5*8,%rsp" in syscall/sysenter code paths, where iret frame needs to be created by hand. Ironically, none of them benefits from this optimization, since all of them need to allocate additional data on stack (struct pt_regs), so they still have to perform subtraction. This patch eliminates KERNEL_STACK_OFFSET. PER_CPU_VAR(kernel_stack) now points directly to top of stack. pt_regs allocations are adjusted to allocate iret frame as well. Hopefully we can merge it later with 32-bit specific PER_CPU_VAR(cpu_current_top_of_stack) variable... Net result in generated code is that constants in several insns are changed. This change is necessary for changing struct pt_regs creation in SYSCALL64 code path from MOV to PUSH instructions. Signed-off-by: Denys Vlasenko Acked-by: Borislav Petkov Acked-by: Andy Lutomirski Cc: Alexei Starovoitov Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Steven Rostedt Cc: Will Drewry Link: http://lkml.kernel.org/r/1426785469-15125-2-git-send-email-dvlasenk@redhat.com Signed-off-by: Ingo Molnar --- arch/x86/xen/smp.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'arch/x86/xen') diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c index 08e8489c47f1..765b7684f858 100644 --- a/arch/x86/xen/smp.c +++ b/arch/x86/xen/smp.c @@ -452,8 +452,7 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct *idle) clear_tsk_thread_flag(idle, TIF_FORK); #endif per_cpu(kernel_stack, cpu) = - (unsigned long)task_stack_page(idle) - - KERNEL_STACK_OFFSET + THREAD_SIZE; + (unsigned long)task_stack_page(idle) + THREAD_SIZE; xen_setup_runstate_info(cpu); xen_setup_timer(cpu); -- cgit v1.2.2 From 3f85483bd80ef1de8cbbf0361be59f6a069b59d4 Mon Sep 17 00:00:00 2001 From: Boris Ostrovsky Date: Wed, 1 Apr 2015 10:12:14 -0400 Subject: x86/cpu: Factor out common CPU initialization code, fix 32-bit Xen PV guests Some of x86 bare-metal and Xen CPU initialization code is common between the two and therefore can be factored out to avoid code duplication. As a side effect, doing so will also extend the fix provided by commit a7fcf28d431e ("x86/asm/entry: Replace this_cpu_sp0() with current_top_of_stack() to x86_32") to 32-bit Xen PV guests. Signed-off-by: Boris Ostrovsky Reviewed-by: David Vrabel Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Thomas Gleixner Cc: konrad.wilk@oracle.com Cc: xen-devel@lists.xenproject.org Link: http://lkml.kernel.org/r/1427897534-5086-1-git-send-email-boris.ostrovsky@oracle.com Signed-off-by: Ingo Molnar --- arch/x86/xen/smp.c | 13 +------------ 1 file changed, 1 insertion(+), 12 deletions(-) (limited to 'arch/x86/xen') diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c index 765b7684f858..7413ee3706d0 100644 --- a/arch/x86/xen/smp.c +++ b/arch/x86/xen/smp.c @@ -445,14 +445,7 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct *idle) { int rc; - per_cpu(current_task, cpu) = idle; -#ifdef CONFIG_X86_32 - irq_ctx_init(cpu); -#else - clear_tsk_thread_flag(idle, TIF_FORK); -#endif - per_cpu(kernel_stack, cpu) = - (unsigned long)task_stack_page(idle) + THREAD_SIZE; + common_cpu_up(cpu, idle); xen_setup_runstate_info(cpu); xen_setup_timer(cpu); @@ -467,10 +460,6 @@ static int xen_cpu_up(unsigned int cpu, struct task_struct *idle) if (rc) return rc; - if (num_online_cpus() == 1) - /* Just in case we booted with a single CPU. */ - alternatives_enable_smp(); - rc = xen_smp_intr_init(cpu); if (rc) return rc; -- cgit v1.2.2