[COMMIT osv master] Partial fix for syscall instruction

[Commit Bot]

From: Nadav Har'El <n...@scylladb.com>
Committer: Pekka Enberg <penb...@scylladb.com>
Branch: master
Partial fix for syscall instruction

We need to set up the LSTAR MSR and friends on each processor - it is not
enough to do it on processor 0. Otherwise, a system call instruction will
always fails if happens to run on any vcpu other than the first one.

With this patch, tst-syscall now passes on my machine with the release
compilation, on both single vcpu (run.py -c1) and many (-c4).
With debug build, the patch still fails - I have other fixes to make it
work.

Refs #791.

Signed-off-by: Nadav Har'El <n...@scylladb.com>
Message-Id: <1472464153-3523-1-git-send-email-...@scylladb.com>
Signed-off-by: Pekka Enberg <penb...@scylladb.com>

---
diff --git a/arch/x64/arch-cpu.hh b/arch/x64/arch-cpu.hh
--- a/arch/x64/arch-cpu.hh
+++ b/arch/x64/arch-cpu.hh
@@ -174,6 +174,8 @@ inline void arch_cpu::init_on_cpu()
     // We can't trust the FPU and the MXCSR to be always initialized to  
default values.
     // In at least one particular version of Xen it is not, leading to  
SIMD exceptions.
     processor::init_fpu();
+
+    processor::init_syscall();
 }

 struct exception_guard {
diff --git a/arch/x64/arch-setup.cc b/arch/x64/arch-setup.cc
--- a/arch/x64/arch-setup.cc
+++ b/arch/x64/arch-setup.cc
@@ -224,8 +224,8 @@ static const int CS_SELECTOR_SHIFT = 3;
 // syscall shift
 static const int IA_32_STAR_SYSCALL_SHIFT = 32;

-static void setup_syscall()
-{
+namespace processor {
+void init_syscall() {
     unsigned long cs = gdt_cs;
     processor::wrmsr(msr::IA32_STAR,  (cs << CS_SELECTOR_SHIFT) <<  
IA_32_STAR_SYSCALL_SHIFT);
     // lstar is where syscall set rip so we set it to syscall_entry
@@ -236,6 +236,7 @@ static void setup_syscall()
     processor::wrmsr(msr::IA32_FMASK, 0);
     processor::wrmsr(msr::IA32_EFER,  processor::rdmsr(msr::IA32_EFER) |  
IA32_EFER_SCE);
 }
+}

 void arch_init_premain()
 {
@@ -244,7 +245,6 @@ void arch_init_premain()
 	debug_early_u64("Error reading disk (real mode): ",  
static_cast<u64>(omb.disk_err));

     disable_pic();
-    setup_syscall();
 }

 #include "drivers/driver.hh"
diff --git a/arch/x64/processor.hh b/arch/x64/processor.hh
--- a/arch/x64/processor.hh
+++ b/arch/x64/processor.hh
@@ -394,6 +394,8 @@ inline void init_fpu()
     asm volatile ("ldmxcsr %0" : : "m" (csr));
 }

+void init_syscall();
+
 inline void lfence()
 {
     asm volatile("lfence");

--
You received this message because you are subscribed to the Google Groups "OSv 
Development" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to osv-dev+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.