2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------ commit c8770e7ba63bb5dd8fe5f9d251275a8fa717fb78 upstream. We now use load_gs_index() to load gs safely; unfortunately this also changes MSR_KERNEL_GS_BASE, which we managed separately. This resulted in confusion and breakage running 32-bit host userspace on a 64-bit kernel. Fix by - saving guest MSR_KERNEL_GS_BASE before we we reload the host's gs - doing the host save/load unconditionally, instead of only when in guest long mode Things can be cleaned up further, but this is the minmal fix for now. Signed-off-by: Avi Kivity <[email protected]> Signed-off-by: Marcelo Tosatti <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> Signed-off-by: Andi Kleen <[email protected]> --- arch/x86/kvm/vmx.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) Index: linux-2.6.35.y/arch/x86/kvm/vmx.c =================================================================== --- linux-2.6.35.y.orig/arch/x86/kvm/vmx.c 2011-03-29 23:53:15.698136001 -0700 +++ linux-2.6.35.y/arch/x86/kvm/vmx.c 2011-03-29 23:53:23.475936985 -0700 @@ -771,10 +771,9 @@ #endif #ifdef CONFIG_X86_64 - if (is_long_mode(&vmx->vcpu)) { - rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base); + rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base); + if (is_long_mode(&vmx->vcpu)) wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base); - } #endif for (i = 0; i < vmx->save_nmsrs; ++i) kvm_set_shared_msr(vmx->guest_msrs[i].index, @@ -789,11 +788,14 @@ ++vmx->vcpu.stat.host_state_reload; vmx->host_state.loaded = 0; +#ifdef CONFIG_X86_64 + if (is_long_mode(&vmx->vcpu)) + rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base); +#endif if (vmx->host_state.gs_ldt_reload_needed) { kvm_load_ldt(vmx->host_state.ldt_sel); #ifdef CONFIG_X86_64 load_gs_index(vmx->host_state.gs_sel); - wrmsrl(MSR_KERNEL_GS_BASE, current->thread.gs); #else loadsegment(gs, vmx->host_state.gs_sel); #endif @@ -802,10 +804,7 @@ loadsegment(fs, vmx->host_state.fs_sel); reload_tss(); #ifdef CONFIG_X86_64 - if (is_long_mode(&vmx->vcpu)) { - rdmsrl(MSR_KERNEL_GS_BASE, vmx->msr_guest_kernel_gs_base); - wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base); - } + wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base); #endif load_gdt(&__get_cpu_var(host_gdt)); } _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
