On Thu, 23 Jul 2015 08:31:41 -0700 Andy Lutomirski <l...@kernel.org> wrote:
> - if (!boot_cpu_has(X86_FEATURE_SEP)) > + /* > + * On 64-bit CPUs, enable SEP unconditionally. On Intel CPUs, > + * it works and we use it. On AMD CPUs, the MSRs exist but EIP > + * is truncated to 32 bits. This doesn't matter because AMD > + * CPUs disallow SYSENTER in long mode. If AMD ever decides to > + * support SYSENTER, then they'll have to fix the truncation > + * issue, and this code will work as-is. > + */ > + > + if (IS_ENABLED(CONFIG_X86_32) && !boot_cpu_has(X86_FEATURE_SEP)) > goto out; > > +#ifdef CONFIG_X86_32 > /* > * We cache MSR_IA32_SYSENTER_CS's value in the TSS's ss1 field -- > * see the big comment in struct x86_hw_tss's definition. > */ > tss->x86_tss.ss1 = __KERNEL_CS; > +#endif > > wrmsrl_safe(MSR_IA32_SYSENTER_CS, __KERNEL_CS); > wrmsrl_safe(MSR_IA32_SYSENTER_ESP, > (unsigned long)tss + > offsetofend(struct tss_struct, SYSENTER_stack)); > +#ifdef CONFIG_X86_32 > wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (unsigned long)entry_SYSENTER_32); > +#else > + wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (unsigned > long)entry_SYSENTER_compat); > +#endif As an additional clean up, what impact would we have to just rename entry_SYSENTER_compat to entry_SYSENTER_32 on x86_64? It would remove the need for the above #ifdef logic. -- Steve > > out: > put_cpu(); > @@ -1187,17 +1201,7 @@ void syscall_init(void) > > #ifdef CONFIG_IA32_EMULATION > wrmsrl(MSR_CSTAR, entry_SYSCALL_compat); > - /* > - * This only works on Intel CPUs. > - * On AMD CPUs these MSRs are 32-bit, CPU truncates > MSR_IA32_SYSENTER_EIP. > - * This does not cause SYSENTER to jump to the wrong location, because > - * AMD doesn't allow SYSENTER in long mode (either 32- or 64-bit). > - */ > - wrmsrl_safe(MSR_IA32_SYSENTER_CS, __KERNEL_CS); > - wrmsrl_safe(MSR_IA32_SYSENTER_ESP, > - (unsigned long)&per_cpu(cpu_tss, smp_processor_id()) + > - offsetofend(struct tss_struct, SYSENTER_stack)); > - wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (unsigned > long)entry_SYSENTER_compat); > + enable_sep_cpu(); > #else > wrmsrl(MSR_CSTAR, ignore_sysret); > wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
