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x86/xen: Support early interrupts in xen pv guests
Add early interrupt handlers activated by idt_setup_early_handler() to the handlers supported by Xen pv guests. This will allow for early WARN() calls not crashing the guest. Suggested-by: Andy Lutomirski <luto@kernel.org> Signed-off-by: Juergen Gross <jgross@suse.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: xen-devel@lists.xenproject.org Cc: boris.ostrovsky@oracle.com Link: https://lkml.kernel.org/r/20171124084221.30172-1-jgross@suse.com
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4 changed files with 53 additions and 14 deletions
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@ -236,11 +236,23 @@
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*/
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#define EARLY_IDT_HANDLER_SIZE 9
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/*
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* xen_early_idt_handler_array is for Xen pv guests: for each entry in
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* early_idt_handler_array it contains a prequel in the form of
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* pop %rcx; pop %r11; jmp early_idt_handler_array[i]; summing up to
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* max 8 bytes.
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*/
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#define XEN_EARLY_IDT_HANDLER_SIZE 8
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#ifndef __ASSEMBLY__
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extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE];
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extern void early_ignore_irq(void);
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#if defined(CONFIG_X86_64) && defined(CONFIG_XEN_PV)
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extern const char xen_early_idt_handler_array[NUM_EXCEPTION_VECTORS][XEN_EARLY_IDT_HANDLER_SIZE];
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#endif
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/*
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* Load a segment. Fall back on loading the zero segment if something goes
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* wrong. This variant assumes that loading zero fully clears the segment.
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@ -1,6 +1,7 @@
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#include <linux/extable.h>
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#include <linux/uaccess.h>
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#include <linux/sched/debug.h>
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#include <xen/xen.h>
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#include <asm/fpu/internal.h>
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#include <asm/traps.h>
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@ -212,8 +213,9 @@ void __init early_fixup_exception(struct pt_regs *regs, int trapnr)
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* Old CPUs leave the high bits of CS on the stack
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* undefined. I'm not sure which CPUs do this, but at least
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* the 486 DX works this way.
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* Xen pv domains are not using the default __KERNEL_CS.
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*/
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if (regs->cs != __KERNEL_CS)
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if (!xen_pv_domain() && regs->cs != __KERNEL_CS)
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goto fail;
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/*
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@ -622,7 +622,7 @@ static struct trap_array_entry trap_array[] = {
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{ simd_coprocessor_error, xen_simd_coprocessor_error, false },
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};
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static bool get_trap_addr(void **addr, unsigned int ist)
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static bool __ref get_trap_addr(void **addr, unsigned int ist)
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{
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unsigned int nr;
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bool ist_okay = false;
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@ -644,6 +644,14 @@ static bool get_trap_addr(void **addr, unsigned int ist)
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}
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}
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if (nr == ARRAY_SIZE(trap_array) &&
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*addr >= (void *)early_idt_handler_array[0] &&
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*addr < (void *)early_idt_handler_array[NUM_EXCEPTION_VECTORS]) {
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nr = (*addr - (void *)early_idt_handler_array[0]) /
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EARLY_IDT_HANDLER_SIZE;
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*addr = (void *)xen_early_idt_handler_array[nr];
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}
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if (WARN_ON(ist != 0 && !ist_okay))
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return false;
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@ -1262,6 +1270,21 @@ asmlinkage __visible void __init xen_start_kernel(void)
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xen_setup_gdt(0);
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xen_init_irq_ops();
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/* Let's presume PV guests always boot on vCPU with id 0. */
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per_cpu(xen_vcpu_id, 0) = 0;
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/*
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* Setup xen_vcpu early because idt_setup_early_handler needs it for
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* local_irq_disable(), irqs_disabled().
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*
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* Don't do the full vcpu_info placement stuff until we have
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* the cpu_possible_mask and a non-dummy shared_info.
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*/
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xen_vcpu_info_reset(0);
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idt_setup_early_handler();
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xen_init_capabilities();
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#ifdef CONFIG_X86_LOCAL_APIC
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@ -1295,18 +1318,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
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*/
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acpi_numa = -1;
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#endif
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/* Let's presume PV guests always boot on vCPU with id 0. */
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per_cpu(xen_vcpu_id, 0) = 0;
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/*
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* Setup xen_vcpu early because start_kernel needs it for
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* local_irq_disable(), irqs_disabled().
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*
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* Don't do the full vcpu_info placement stuff until we have
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* the cpu_possible_mask and a non-dummy shared_info.
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*/
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xen_vcpu_info_reset(0);
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WARN_ON(xen_cpuhp_setup(xen_cpu_up_prepare_pv, xen_cpu_dead_pv));
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local_irq_disable();
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@ -15,6 +15,7 @@
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#include <xen/interface/xen.h>
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#include <linux/init.h>
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#include <linux/linkage.h>
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.macro xen_pv_trap name
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@ -54,6 +55,19 @@ xen_pv_trap entry_INT80_compat
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#endif
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xen_pv_trap hypervisor_callback
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__INIT
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ENTRY(xen_early_idt_handler_array)
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i = 0
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.rept NUM_EXCEPTION_VECTORS
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pop %rcx
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pop %r11
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jmp early_idt_handler_array + i*EARLY_IDT_HANDLER_SIZE
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i = i + 1
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.fill xen_early_idt_handler_array + i*XEN_EARLY_IDT_HANDLER_SIZE - ., 1, 0xcc
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.endr
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END(xen_early_idt_handler_array)
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__FINIT
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hypercall_iret = hypercall_page + __HYPERVISOR_iret * 32
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/*
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* Xen64 iret frame:
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