Re: [PATCH v5 07/12] x86/traps: Add #VE support for TDX guest
From: Kuppuswamy, Sathyanarayanan
Date: Tue Aug 24 2021 - 13:43:11 EST
On 8/24/21 3:17 AM, Borislav Petkov wrote:
On Wed, Aug 04, 2021 at 11:13:24AM -0700, Kuppuswamy Sathyanarayanan wrote:
If a guest kernel action which would normally cause a #VE occurs in the
interrupt-disabled region before TDGETVEINFO, a #DF is delivered to the
guest which will result in an oops (and should eventually be a panic, as
we would like to set panic_on_oops to 1 for TDX guests).
Who's "we"?
Please use passive voice in your commit message and comments: no "we"
or "I", etc. Personal pronouns are ambiguous in text, especially with
so many parties/companies/etc developing the kernel so let's avoid them.
Audit all your patchsets pls.
Sorry. I will fix this in next version.
Add basic infrastructure to handle any #VE which occurs in the kernel or
userspace. Later patches will add handling for specific #VE scenarios.
Convert unhandled #VE's (everything, until later in this series) so that
they appear just like a #GP by calling ve_raise_fault() directly.
ve_raise_fault() is similar to #GP handler and is responsible for
sending SIGSEGV to userspace and cpu die and notifying debuggers and
In all your text:
s/cpu/CPU/g
Audit all your patchsets pls.
Yes. I will fix this in next version.
@@ -53,6 +67,11 @@ u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
u64 __tdx_hypercall(u64 type, u64 fn, u64 r12, u64 r13, u64 r14,
u64 r15, struct tdx_hypercall_output *out);
+unsigned long tdg_get_ve_info(struct ve_info *ve);
+
+int tdg_handle_virtualization_exception(struct pt_regs *regs,
There's that "tdg" prefix again. Please fix all your patchsets.
Mainly chose it avoid future name conflicts with KVM (tdx) calls. But
if you don't like "tdg", I can change it back to "tdx" and resolve the
naming issues when it occurs.
static struct {
unsigned int gpa_width;
@@ -75,6 +76,41 @@ static void tdg_get_info(void)
td_info.attributes = out.rdx;
}
+unsigned long tdg_get_ve_info(struct ve_info *ve)
+{
+ u64 ret;
+ struct tdx_module_output out = {0};
The tip-tree preferred ordering of variable declarations at the
beginning of a function is reverse fir tree order::
struct long_struct_name *descriptive_name;
unsigned long foo, bar;
unsigned int tmp;
int ret;
The above is faster to parse than the reverse ordering::
int ret;
unsigned int tmp;
unsigned long foo, bar;
struct long_struct_name *descriptive_name;
And even more so than random ordering::
unsigned long foo, bar;
int ret;
struct long_struct_name *descriptive_name;
unsigned int tmp;
Yes. I will fix this in next version.
+int tdg_handle_virtualization_exception(struct pt_regs *regs,
+ struct ve_info *ve)
+{
+ /*
+ * TODO: Add handler support for various #VE exit
+ * reasons. It will be added by other patches in
+ * the series.
+ */
That comment needs to go.
Ok. I will remove it.
+#ifdef CONFIG_INTEL_TDX_GUEST
+#define VEFSTR "VE fault"
+static void ve_raise_fault(struct pt_regs *regs, long error_code)
+{
+ struct task_struct *tsk = current;
+
+ if (user_mode(regs)) {
+ tsk->thread.error_code = error_code;
+ tsk->thread.trap_nr = X86_TRAP_VE;
+
+ /*
+ * Not fixing up VDSO exceptions similar to #GP handler
+ * because we don't expect the VDSO to trigger #VE.
+ */
+ show_signal(tsk, SIGSEGV, "", VEFSTR, regs, error_code);
+ force_sig(SIGSEGV);
+ return;
+ }
+
+ if (fixup_exception(regs, X86_TRAP_VE, error_code, 0))
There are exception table entries which can trigger a #VE?
It is required to handle #VE exceptions raised by unhandled MSR
read/writes.
+ return;
+
+ tsk->thread.error_code = error_code;
+ tsk->thread.trap_nr = X86_TRAP_VE;
+
+ /*
+ * To be potentially processing a kprobe fault and to trust the result
+ * from kprobe_running(), we have to be non-preemptible.
+ */
+ if (!preemptible() &&
+ kprobe_running() &&
+ kprobe_fault_handler(regs, X86_TRAP_VE))
+ return;
+
+ notify_die(DIE_GPF, VEFSTR, regs, error_code, X86_TRAP_VE, SIGSEGV);
Other handlers check that retval.
Ok. I can check it. But there is only one statement after this call. So it
may not be very helpful.
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer