On Mon, Sep 13 2021 at 13:01, Sohil Mehta wrote:
SENDUIPI is a special ring-3 instruction that makes a supervisor mode memory access to the UPID and UITT memory. Currently, KPTI needs to be off for User IPIs to work. Processors that support user interrupts are not affected by Meltdown so the auto mode of KPTI will default to off.
Users who want to force enable KPTI will need to wait for a later version of this patch series that is compatible with KPTI. We need to allocate the UPID and UITT structures from a special memory region that has supervisor access but it is mapped into userspace. The plan is to implement a mechanism similar to LDT.
Seriously?
Signed-off-by: Jacob Pan jacob.jun.pan@linux.intel.com Signed-off-by: Sohil Mehta sohil.mehta@intel.com
This SOB chain is invalid. Ditto in several other patches.
+config X86_USER_INTERRUPTS
- bool "User Interrupts (UINTR)"
- depends on X86_LOCAL_APIC && X86_64
X86_64 does not work w/o LOCAL_APIC so this dependency is pointless.
- depends on CPU_SUP_INTEL
- help
User Interrupts are events that can be delivered directly touserspace without a transition through the kernel. The interruptscould be generated by another userspace application, kernel or adevice.Refer, Documentation/x86/user-interrupts.rst for details.
"Refer, Documentation..." is not a sentence.
+/* User Interrupt interface */ +#define MSR_IA32_UINTR_RR 0x985 +#define MSR_IA32_UINTR_HANDLER 0x986 +#define MSR_IA32_UINTR_STACKADJUST 0x987 +#define MSR_IA32_UINTR_MISC 0x988 /* 39:32-UINV, 31:0-UITTSZ */
Bah, these tail comments are crap. Please define proper masks/shift constants for this instead of using magic numbers in the code.
+static __always_inline void setup_uintr(struct cpuinfo_x86 *c)
This has to be always inline because it's performance critical or what?
+{
- /* check the boot processor, plus compile options for UINTR. */
Sentences start with uppercase letters.
- if (!cpu_feature_enabled(X86_FEATURE_UINTR))
goto disable_uintr;- /* checks the current processor's cpuid bits: */
- if (!cpu_has(c, X86_FEATURE_UINTR))
goto disable_uintr;- /*
* User Interrupts currently doesn't support PTI. For processors that* support User interrupts PTI in auto mode will default to off. Need* this check only for users who have force enabled PTI.*/- if (boot_cpu_has(X86_FEATURE_PTI)) {
pr_info_once("x86: User Interrupts (UINTR) not enabled. Please disable PTI using 'nopti' kernel parameter\n");
That message does not make sense. The admin has explicitly added 'pti' to the kernel command line on a CPU which is not affected. So why would he now have to add 'nopti' ?
Thanks,
tglx