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When FRED is enabled, its initialization message is printed for every CPU during boot as well as during suspend-resume. This debug message can be noisy and it isn't very useful unless someone is debugging FRED itself. As FRED is enabled by default, remove the log message as mentioned in the code comment. Signed-off-by: Sohil Mehta <sohil.mehta@intel.com> Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://patch.msgid.link/20260325230151.1898287-4-hpa@zytor.com
91 lines
3.0 KiB
C
91 lines
3.0 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#include <linux/kernel.h>
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#include <asm/desc.h>
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#include <asm/fred.h>
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#include <asm/msr.h>
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#include <asm/tlbflush.h>
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#include <asm/traps.h>
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/* #DB in the kernel would imply the use of a kernel debugger. */
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#define FRED_DB_STACK_LEVEL 1UL
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#define FRED_NMI_STACK_LEVEL 2UL
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#define FRED_MC_STACK_LEVEL 2UL
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/*
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* #DF is the highest level because a #DF means "something went wrong
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* *while delivering an exception*." The number of cases for which that
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* can happen with FRED is drastically reduced and basically amounts to
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* "the stack you pointed me to is broken." Thus, always change stacks
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* on #DF, which means it should be at the highest level.
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*/
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#define FRED_DF_STACK_LEVEL 3UL
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#define FRED_STKLVL(vector, lvl) ((lvl) << (2 * (vector)))
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DEFINE_PER_CPU(unsigned long, fred_rsp0);
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EXPORT_PER_CPU_SYMBOL(fred_rsp0);
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void cpu_init_fred_exceptions(void)
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{
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/*
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* If a kernel event is delivered before a CPU goes to user level for
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* the first time, its SS is NULL thus NULL is pushed into the SS field
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* of the FRED stack frame. But before ERETS is executed, the CPU may
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* context switch to another task and go to user level. Then when the
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* CPU comes back to kernel mode, SS is changed to __KERNEL_DS. Later
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* when ERETS is executed to return from the kernel event handler, a #GP
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* fault is generated because SS doesn't match the SS saved in the FRED
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* stack frame.
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*
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* Initialize SS to __KERNEL_DS when enabling FRED to avoid such #GPs.
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*/
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loadsegment(ss, __KERNEL_DS);
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wrmsrq(MSR_IA32_FRED_CONFIG,
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/* Reserve for CALL emulation */
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FRED_CONFIG_REDZONE |
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FRED_CONFIG_INT_STKLVL(0) |
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FRED_CONFIG_ENTRYPOINT(asm_fred_entrypoint_user));
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wrmsrq(MSR_IA32_FRED_STKLVLS, 0);
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/*
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* Ater a CPU offline/online cycle, the FRED RSP0 MSR should be
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* resynchronized with its per-CPU cache.
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*/
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wrmsrq(MSR_IA32_FRED_RSP0, __this_cpu_read(fred_rsp0));
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wrmsrq(MSR_IA32_FRED_RSP1, 0);
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wrmsrq(MSR_IA32_FRED_RSP2, 0);
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wrmsrq(MSR_IA32_FRED_RSP3, 0);
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/* Enable FRED */
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cr4_set_bits(X86_CR4_FRED);
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/* Any further IDT use is a bug */
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idt_invalidate();
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/* Use int $0x80 for 32-bit system calls in FRED mode */
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setup_clear_cpu_cap(X86_FEATURE_SYSFAST32);
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setup_clear_cpu_cap(X86_FEATURE_SYSCALL32);
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}
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/* Must be called after setup_cpu_entry_areas() */
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void cpu_init_fred_rsps(void)
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{
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/*
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* The purpose of separate stacks for NMI, #DB and #MC *in the kernel*
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* (remember that user space faults are always taken on stack level 0)
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* is to avoid overflowing the kernel stack.
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*/
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wrmsrq(MSR_IA32_FRED_STKLVLS,
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FRED_STKLVL(X86_TRAP_DB, FRED_DB_STACK_LEVEL) |
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FRED_STKLVL(X86_TRAP_NMI, FRED_NMI_STACK_LEVEL) |
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FRED_STKLVL(X86_TRAP_MC, FRED_MC_STACK_LEVEL) |
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FRED_STKLVL(X86_TRAP_DF, FRED_DF_STACK_LEVEL));
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/* The FRED equivalents to IST stacks... */
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wrmsrq(MSR_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB));
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wrmsrq(MSR_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI));
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wrmsrq(MSR_IA32_FRED_RSP3, __this_cpu_ist_top_va(DF));
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}
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