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Message-Id: <20221109145156.84714-10-pbonzini@redhat.com>
Date: Wed, 9 Nov 2022 09:51:54 -0500
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc: thomas.lendacky@....com, jmattson@...gle.com, seanjc@...gle.com,
stable@...r.kernel.org, Nathan Chancellor <nathan@...nel.org>,
Andrew Cooper <andrew.cooper3@...rix.com>
Subject: [PATCH 09/11] KVM: SVM: restore host save area from assembly
Allow access to the percpu area via the GS segment base, which is
needed in order to access the saved host spec_ctrl value. In linux-next
FILL_RETURN_BUFFER also needs to access percpu data.
For simplicity, the physical address of the save area is added to struct
svm_cpu_data.
Cc: stable@...r.kernel.org
Fixes: a149180fbcf3 ("x86: Add magic AMD return-thunk")
Reported-by: Nathan Chancellor <nathan@...nel.org>
Analyzed-by: Andrew Cooper <andrew.cooper3@...rix.com>
Tested-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
arch/x86/kvm/kvm-asm-offsets.c | 1 +
arch/x86/kvm/svm/svm.c | 14 ++++++--------
arch/x86/kvm/svm/svm.h | 2 ++
arch/x86/kvm/svm/svm_ops.h | 5 -----
arch/x86/kvm/svm/vmenter.S | 17 +++++++++++++++++
5 files changed, 26 insertions(+), 13 deletions(-)
diff --git a/arch/x86/kvm/kvm-asm-offsets.c b/arch/x86/kvm/kvm-asm-offsets.c
index f83e88b85bf2..1b805cd24d66 100644
--- a/arch/x86/kvm/kvm-asm-offsets.c
+++ b/arch/x86/kvm/kvm-asm-offsets.c
@@ -18,6 +18,7 @@ static void __used common(void)
OFFSET(SVM_current_vmcb, vcpu_svm, current_vmcb);
OFFSET(SVM_vmcb01, vcpu_svm, vmcb01);
OFFSET(KVM_VMCB_pa, kvm_vmcb_info, pa);
+ OFFSET(SD_save_area_pa, svm_cpu_data, save_area_pa);
}
if (IS_ENABLED(CONFIG_KVM_INTEL)) {
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 4e3a47eb5002..469c1b5617af 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -592,7 +592,7 @@ static int svm_hardware_enable(void)
wrmsrl(MSR_EFER, efer | EFER_SVME);
- wrmsrl(MSR_VM_HSAVE_PA, __sme_page_pa(sd->save_area));
+ wrmsrl(MSR_VM_HSAVE_PA, sd->save_area_pa);
if (static_cpu_has(X86_FEATURE_TSCRATEMSR)) {
/*
@@ -648,6 +648,7 @@ static void svm_cpu_uninit(int cpu)
kfree(sd->sev_vmcbs);
__free_page(sd->save_area);
+ sd->save_area_pa = 0;
sd->save_area = NULL;
}
@@ -665,6 +666,7 @@ static int svm_cpu_init(int cpu)
if (ret)
goto free_save_area;
+ sd->save_area_pa = __sme_page_pa(sd->save_area);
return 0;
free_save_area:
@@ -1450,7 +1452,7 @@ static void svm_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
* Save additional host state that will be restored on VMEXIT (sev-es)
* or subsequent vmload of host save area.
*/
- vmsave(__sme_page_pa(sd->save_area));
+ vmsave(sd->save_area_pa);
if (sev_es_guest(vcpu->kvm)) {
struct sev_es_save_area *hostsa;
hostsa = (struct sev_es_save_area *)(page_address(sd->save_area) + 0x400);
@@ -3905,14 +3907,10 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu)
guest_state_enter_irqoff();
- if (sev_es_guest(vcpu->kvm)) {
+ if (sev_es_guest(vcpu->kvm))
__svm_sev_es_vcpu_run(svm);
- } else {
- struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, vcpu->cpu);
-
+ else
__svm_vcpu_run(svm);
- vmload(__sme_page_pa(sd->save_area));
- }
guest_state_exit_irqoff();
}
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 2af6a71126c1..83955a4e520e 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -287,6 +287,8 @@ struct svm_cpu_data {
struct kvm_ldttss_desc *tss_desc;
struct page *save_area;
+ unsigned long save_area_pa;
+
struct vmcb *current_vmcb;
/* index = sev_asid, value = vmcb pointer */
diff --git a/arch/x86/kvm/svm/svm_ops.h b/arch/x86/kvm/svm/svm_ops.h
index 9430d6437c9f..36c8af87a707 100644
--- a/arch/x86/kvm/svm/svm_ops.h
+++ b/arch/x86/kvm/svm/svm_ops.h
@@ -61,9 +61,4 @@ static __always_inline void vmsave(unsigned long pa)
svm_asm1(vmsave, "a" (pa), "memory");
}
-static __always_inline void vmload(unsigned long pa)
-{
- svm_asm1(vmload, "a" (pa), "memory");
-}
-
#endif /* __KVM_X86_SVM_OPS_H */
diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S
index 5bc2ed7d79c0..57440acfc73e 100644
--- a/arch/x86/kvm/svm/vmenter.S
+++ b/arch/x86/kvm/svm/vmenter.S
@@ -49,6 +49,14 @@ SYM_FUNC_START(__svm_vcpu_run)
#endif
push %_ASM_BX
+ /*
+ * Save variables needed after vmexit on the stack, in inverse
+ * order compared to when they are needed.
+ */
+
+ /* Needed to restore access to percpu variables. */
+ __ASM_SIZE(push) PER_CPU_VAR(svm_data + SD_save_area_pa)
+
/* Save @svm. */
push %_ASM_ARG1
@@ -124,6 +132,11 @@ SYM_FUNC_START(__svm_vcpu_run)
5: vmsave %_ASM_AX
6:
+ /* Restores GSBASE among other things, allowing access to percpu data. */
+ pop %_ASM_AX
+7: vmload %_ASM_AX
+8:
+
#ifdef CONFIG_RETPOLINE
/* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */
FILL_RETURN_BUFFER %_ASM_AX, RSB_CLEAR_LOOPS, X86_FEATURE_RETPOLINE
@@ -187,10 +200,14 @@ SYM_FUNC_START(__svm_vcpu_run)
50: cmpb $0, kvm_rebooting
jne 6b
ud2
+70: cmpb $0, kvm_rebooting
+ jne 8b
+ ud2
_ASM_EXTABLE(1b, 10b)
_ASM_EXTABLE(3b, 30b)
_ASM_EXTABLE(5b, 50b)
+ _ASM_EXTABLE(7b, 70b)
SYM_FUNC_END(__svm_vcpu_run)
--
2.31.1
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