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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2022-01-10 10:09:22 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-01-10 10:09:22 -0800 |
| commit | 25f8c7785e254779fbd2127c4eced81811e8e421 (patch) | |
| tree | 3b377bd739e5a7d94a2bb50398387a2322028d51 | |
| parent | 308319e990ae95b2a752fa0a1730f88598ca0dc7 (diff) | |
| parent | 244122b4d2e5221e6abd6e21d6a58170104db781 (diff) | |
| download | trivial-25f8c7785e254779fbd2127c4eced81811e8e421.tar.gz | |
Merge tag 'x86_cpu_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 cpuid updates from Borislav Petkov:
- Enable the short string copies for CPUs which support them, in
copy_user_enhanced_fast_string()
- Avoid writing MSR_CSTAR on Intel due to TDX guests raising a #VE trap
* tag 'x86_cpu_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/lib: Add fast-short-rep-movs check to copy_user_enhanced_fast_string()
x86/cpu: Don't write CSTAR MSR on Intel CPUs
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 15 | ||||
| -rw-r--r-- | arch/x86/lib/copy_user_64.S | 4 |
2 files changed, 15 insertions, 4 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 79b3d67addcc3..7b8382c117889 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1787,6 +1787,17 @@ EXPORT_PER_CPU_SYMBOL(__preempt_count); DEFINE_PER_CPU(unsigned long, cpu_current_top_of_stack) = TOP_OF_INIT_STACK; +static void wrmsrl_cstar(unsigned long val) +{ + /* + * Intel CPUs do not support 32-bit SYSCALL. Writing to MSR_CSTAR + * is so far ignored by the CPU, but raises a #VE trap in a TDX + * guest. Avoid the pointless write on all Intel CPUs. + */ + if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) + wrmsrl(MSR_CSTAR, val); +} + /* May not be marked __init: used by software suspend */ void syscall_init(void) { @@ -1794,7 +1805,7 @@ void syscall_init(void) wrmsrl(MSR_LSTAR, (unsigned long)entry_SYSCALL_64); #ifdef CONFIG_IA32_EMULATION - wrmsrl(MSR_CSTAR, (unsigned long)entry_SYSCALL_compat); + wrmsrl_cstar((unsigned long)entry_SYSCALL_compat); /* * This only works on Intel CPUs. * On AMD CPUs these MSRs are 32-bit, CPU truncates MSR_IA32_SYSENTER_EIP. @@ -1806,7 +1817,7 @@ void syscall_init(void) (unsigned long)(cpu_entry_stack(smp_processor_id()) + 1)); wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)entry_SYSENTER_compat); #else - wrmsrl(MSR_CSTAR, (unsigned long)ignore_sysret); + wrmsrl_cstar((unsigned long)ignore_sysret); wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)GDT_ENTRY_INVALID_SEG); wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL); wrmsrl_safe(MSR_IA32_SYSENTER_EIP, 0ULL); diff --git a/arch/x86/lib/copy_user_64.S b/arch/x86/lib/copy_user_64.S index 2797e630b9b1c..1c429f0489ddc 100644 --- a/arch/x86/lib/copy_user_64.S +++ b/arch/x86/lib/copy_user_64.S @@ -200,8 +200,8 @@ EXPORT_SYMBOL(copy_user_generic_string) */ SYM_FUNC_START(copy_user_enhanced_fast_string) ASM_STAC - cmpl $64,%edx - jb .L_copy_short_string /* less then 64 bytes, avoid the costly 'rep' */ + /* CPUs without FSRM should avoid rep movsb for short copies */ + ALTERNATIVE "cmpl $64, %edx; jb .L_copy_short_string", "", X86_FEATURE_FSRM movl %edx,%ecx 1: rep movsb |