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Message-ID: <20241121201448.36170-7-adrian.hunter@intel.com>
Date: Thu, 21 Nov 2024 22:14:45 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: pbonzini@...hat.com,
seanjc@...gle.com,
kvm@...r.kernel.org,
dave.hansen@...ux.intel.com
Cc: rick.p.edgecombe@...el.com,
kai.huang@...el.com,
adrian.hunter@...el.com,
reinette.chatre@...el.com,
xiaoyao.li@...el.com,
tony.lindgren@...ux.intel.com,
binbin.wu@...ux.intel.com,
dmatlack@...gle.com,
isaku.yamahata@...el.com,
nik.borisov@...e.com,
linux-kernel@...r.kernel.org,
x86@...nel.org,
yan.y.zhao@...el.com,
chao.gao@...el.com,
weijiang.yang@...el.com
Subject: [PATCH 6/7] KVM: TDX: restore user ret MSRs
From: Isaku Yamahata <isaku.yamahata@...el.com>
Several user ret MSRs are clobbered on TD exit. Restore those values on
TD exit and before returning to ring 3. Because TSX_CTRL requires special
treatment, this patch doesn't address it.
Co-developed-by: Tony Lindgren <tony.lindgren@...ux.intel.com>
Signed-off-by: Tony Lindgren <tony.lindgren@...ux.intel.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
---
TD vcpu enter/exit v1:
- Rename tdx_user_return_update_cache() ->
tdx_user_return_msr_update_cache() (extrapolated from Binbin)
- Adjust to rename in previous patches (Binbin)
- Simplify comment (Tony)
- Move code change in tdx_hardware_setup() to __tdx_bringup().
---
arch/x86/kvm/vmx/tdx.c | 42 +++++++++++++++++++++++++++++++++++++++++-
1 file changed, 41 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 00fdd2932205..4a33ca54c8ba 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -2,7 +2,6 @@
#include <linux/cleanup.h>
#include <linux/cpu.h>
#include <linux/mmu_context.h>
-
#include <asm/fpu/xcr.h>
#include <asm/tdx.h>
#include "capabilities.h"
@@ -711,6 +710,28 @@ void tdx_vcpu_free(struct kvm_vcpu *vcpu)
}
+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_restore_host_xsave_state(struct kvm_vcpu *vcpu)
{
struct kvm_tdx *kvm_tdx = to_kvm_tdx(vcpu->kvm);
@@ -796,6 +817,7 @@ fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
tdx_vcpu_enter_exit(vcpu);
+ tdx_user_return_msr_update_cache();
tdx_restore_host_xsave_state(vcpu);
tdx->host_state_need_restore = true;
@@ -2233,6 +2255,24 @@ static int __init __tdx_bringup(void)
for_each_possible_cpu(i)
INIT_LIST_HEAD(&per_cpu(associated_tdvcpus, 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,
* as making SEAMCALLs requires CPU being in post-VMXON state.
--
2.43.0
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