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KVM: TDX: restore user ret MSRs

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Several MSRs are clobbered on TD exit that are not used by Linux while
in ring 0.  Ensure the cached value of the MSR is updated on vcpu_put,
and the MSRs themselves before returning to ring 3.

Co-developed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Signed-off-by: Tony Lindgren <tony.lindgren@linux.intel.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20250129095902.16391-10-adrian.hunter@intel.com>
Reviewed-by: Xiayao Li <xiaoyao.li@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Isaku Yamahata
2025-01-29 11:58:58 +02:00
committed by Paolo Bonzini
parent d3a6b6cfb8
commit e0b4f31a3c
2 changed files with 51 additions and 1 deletions
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51
arch/x86/kvm/vmx/tdx.c
View File

@@ -651,9 +651,32 @@ void tdx_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
vt->guest_state_loaded = true;
}
struct tdx_uret_msr {
u32 msr;
unsigned int slot;
u64 defval;
};
static struct tdx_uret_msr tdx_uret_msrs[] = {
{.msr = MSR_SYSCALL_MASK, .defval = 0x20200 },
{.msr = MSR_STAR,},
{.msr = MSR_LSTAR,},
{.msr = MSR_TSC_AUX,},
};
static void tdx_user_return_msr_update_cache(void)
{
int i;
for (i = 0; i < ARRAY_SIZE(tdx_uret_msrs); i++)
kvm_user_return_msr_update_cache(tdx_uret_msrs[i].slot,
tdx_uret_msrs[i].defval);
}
static void tdx_prepare_switch_to_host(struct kvm_vcpu *vcpu)
{
struct vcpu_vt *vt = to_vt(vcpu);
struct vcpu_tdx *tdx = to_tdx(vcpu);
if (!vt->guest_state_loaded)
return;
@@ -661,6 +684,11 @@ static void tdx_prepare_switch_to_host(struct kvm_vcpu *vcpu)
++vcpu->stat.host_state_reload;
wrmsrl(MSR_KERNEL_GS_BASE, vt->msr_host_kernel_gs_base);
if (tdx->guest_entered) {
tdx_user_return_msr_update_cache();
tdx->guest_entered = false;
}
vt->guest_state_loaded = false;
}
@@ -767,6 +795,8 @@ EXPORT_SYMBOL_GPL(kvm_load_host_xsave_state);
fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
{
struct vcpu_tdx *tdx = to_tdx(vcpu);
/*
* force_immediate_exit requires vCPU entering for events injection with
* an immediately exit followed. But The TDX module doesn't guarantee
@@ -782,6 +812,7 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
tdx_vcpu_enter_exit(vcpu);
tdx_load_host_xsave_state(vcpu);
tdx->guest_entered = true;
vcpu->arch.regs_avail &= TDX_REGS_AVAIL_SET;
@@ -2242,7 +2273,25 @@ static int __init __do_tdx_bringup(void)
static int __init __tdx_bringup(void)
{
const struct tdx_sys_info_td_conf *td_conf;
int r;
int r, i;
for (i = 0; i < ARRAY_SIZE(tdx_uret_msrs); i++) {
/*
* Check if MSRs (tdx_uret_msrs) can be saved/restored
* before returning to user space.
*
* this_cpu_ptr(user_return_msrs)->registered isn't checked
* because the registration is done at vcpu runtime by
* tdx_user_return_msr_update_cache().
*/
tdx_uret_msrs[i].slot = kvm_find_user_return_msr(tdx_uret_msrs[i].msr);
if (tdx_uret_msrs[i].slot == -1) {
/* If any MSR isn't supported, it is a KVM bug */
pr_err("MSR %x isn't included by kvm_find_user_return_msr\n",
tdx_uret_msrs[i].msr);
return -EIO;
}
}
/*
* Enabling TDX requires enabling hardware virtualization first,

1
arch/x86/kvm/vmx/tdx.h
View File

@@ -57,6 +57,7 @@ struct vcpu_tdx {
u64 vp_enter_ret;
enum vcpu_tdx_state state;
bool guest_entered;
};
void tdh_vp_rd_failed(struct vcpu_tdx *tdx, char *uclass, u32 field, u64 err);