diff options
| -rw-r--r-- | pkg/ring0/kernel_amd64.go | 22 |
1 files changed, 5 insertions, 17 deletions
diff --git a/pkg/ring0/kernel_amd64.go b/pkg/ring0/kernel_amd64.go index 41dfd0bf9..f63af8b76 100644 --- a/pkg/ring0/kernel_amd64.go +++ b/pkg/ring0/kernel_amd64.go @@ -254,6 +254,8 @@ func (c *CPU) SwitchToUser(switchOpts SwitchOpts) (vector Vector) { return } +var sentryXCR0 = xgetbv(0) + // start is the CPU entrypoint. // // This is called from the Start asm stub (see entry_amd64.go); on return the @@ -265,24 +267,10 @@ func start(c *CPU) { WriteGS(kernelAddr(c.kernelEntry)) WriteFS(uintptr(c.registers.Fs_base)) - // Initialize floating point. - // - // Note that on skylake, the valid XCR0 mask reported seems to be 0xff. - // This breaks down as: - // - // bit0 - x87 - // bit1 - SSE - // bit2 - AVX - // bit3-4 - MPX - // bit5-7 - AVX512 - // - // For some reason, enabled MPX & AVX512 on platforms that report them - // seems to be cause a general protection fault. (Maybe there are some - // virtualization issues and these aren't exported to the guest cpuid.) - // This needs further investigation, but we can limit the floating - // point operations to x87, SSE & AVX for now. fninit() - xsetbv(0, validXCR0Mask&0x7) + // Need to sync XCR0 with the host, because xsave and xrstor can be + // called from different contexts. + xsetbv(0, sentryXCR0) // Set the syscall target. wrmsr(_MSR_LSTAR, kernelFunc(sysenter)) |