KVM: x86: Play nice with protected guests in complete_hypercall_exit()

sean-jc · gregkh · commit 7ed4db315094 · 2024-12-27T13:52:59.000+01:00
commit 9b42d1e upstream. Use is_64_bit_hypercall() instead of is_64_bit_mode() to detect a 64-bit hypercall when completing said hypercall. For guests with protected state, e.g. SEV-ES and SEV-SNP, KVM must assume the hypercall was made in 64-bit mode as the vCPU state needed to detect 64-bit mode is unavailable. Hacking the sev_smoke_test selftest to generate a KVM_HC_MAP_GPA_RANGE hypercall via VMGEXIT trips the WARN: ------------[ cut here ]------------ WARNING: CPU: 273 PID: 326626 at arch/x86/kvm/x86.h:180 complete_hypercall_exit+0x44/0xe0 [kvm] Modules linked in: kvm_amd kvm ... [last unloaded: kvm] CPU: 273 UID: 0 PID: 326626 Comm: sev_smoke_test Not tainted 6.12.0-smp--392e932fa0f3-feat torvalds#470 Hardware name: Google Astoria/astoria, BIOS 0.20240617.0-0 06/17/2024 RIP: 0010:complete_hypercall_exit+0x44/0xe0 [kvm] Call Trace: <TASK> kvm_arch_vcpu_ioctl_run+0x2400/0x2720 [kvm] kvm_vcpu_ioctl+0x54f/0x630 [kvm] __se_sys_ioctl+0x6b/0xc0 do_syscall_64+0x83/0x160 entry_SYSCALL_64_after_hwframe+0x76/0x7e </TASK> ---[ end trace 0000000000000000 ]--- Fixes: b5aead0 ("KVM: x86: Assume a 64-bit hypercall for guests with protected state") Cc: stable@vger.kernel.org Cc: Tom Lendacky <thomas.lendacky@amd.com> Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com> Reviewed-by: Nikunj A Dadhania <nikunj@amd.com> Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com> Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com> Reviewed-by: Kai Huang <kai.huang@intel.com> Link: https://lore.kernel.org/r/20241128004344.4072099-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
@@ -9712,7 +9712,7 @@ static int complete_hypercall_exit(struct kvm_vcpu *vcpu)
 {
 	u64 ret = vcpu->run->hypercall.ret;
 
-	if (!is_64_bit_mode(vcpu))
+	if (!is_64_bit_hypercall(vcpu))
 		ret = (u32)ret;
 	kvm_rax_write(vcpu, ret);
 	++vcpu->stat.hypercalls;

Original file line number	Diff line number	Diff line change
`@@ -9712,7 +9712,7 @@ static int complete_hypercall_exit(struct kvm_vcpu *vcpu)`
`9712`	`9712`	`{`
`9713`	`9713`	`u64 ret = vcpu->run->hypercall.ret;`
`9714`	`9714`
`9715`		`- if (!is_64_bit_mode(vcpu))`
	`9715`	`+ if (!is_64_bit_hypercall(vcpu))`
`9716`	`9716`	`ret = (u32)ret;`
`9717`	`9717`	`kvm_rax_write(vcpu, ret);`
`9718`	`9718`	`++vcpu->stat.hypercalls;`