linux-kernel - [PATCH v2 7/9] x86: Use current USER_CS to setup correct context on vmx entry

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Date:   Thu,  1 Oct 2020 16:58:17 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     luto@...nel.org, tglx@...utronix.de
Cc:     hch@....de, hpa@...or.com, bp@...en8.de, rric@...nel.org,
        peterz@...radead.org, mingo@...hat.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, dave.hansen@...ux.intel.com,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel@...labora.com
Subject: [PATCH v2 7/9] x86: Use current USER_CS to setup correct context on vmx entry

vmx_prepare_switch_to_guest shouldn't use is_64bit_mm, which has a
very specific use in uprobes.  Use the user_64bit_mode helper instead.
This reduces the usage of is_64bit_mm, which is awkward, since it relies
on the personality at load time, which is fine for uprobes, but doesn't
seem fine here.

I tested this by running VMs with 64 and 32 bits payloads from 64/32
programs.

Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
---
 arch/x86/kvm/vmx/vmx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 7b2a068f08c1..b5aafd9e5f5d 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -1172,7 +1172,7 @@ void vmx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
 	savesegment(es, host_state->es_sel);
 
 	gs_base = cpu_kernelmode_gs_base(cpu);
-	if (likely(is_64bit_mm(current->mm))) {
+	if (likely(user_64bit_mode(current_pt_regs()))) {
 		current_save_fsgs();
 		fs_sel = current->thread.fsindex;
 		gs_sel = current->thread.gsindex;
-- 
2.28.0