Merge branch 'svm' of https://github.com/kvm-x86/linux into HEAD

Clean up SVM's enter/exit assembly code so that it can be compiled without OBJECT_FILES_NON_STANDARD. The "standard" __svm_vcpu_run() can't be made 100% bulletproof, as RBP isn't restored on #VMEXIT, but that's also the case for __vmx_vcpu_run(), and getting "close enough" is better than not even trying. As for SEV-ES, after yet another refresher on swap types, I realized KVM can simply let the hardware restore registers after #VMEXIT, all that's missing is storing the current values to the host save area (they are swap type B). This should provide 100% accuracy when using stack frames for unwinding, and requires less assembly. In between, build the SEV-ES code iff CONFIG_KVM_AMD_SEV=y, and yank out "support" for 32-bit kernels in __svm_sev_es_vcpu_run, which was unnecessarily polluting the code for a configuration that is disabled at build time. Signed-off-by: Paolo Bonzini <[email protected]>
sirdarckcat · Apr 17, 2024 · 44ecfa3 · 44ecfa3
2 parents 1c3bed8 + 27ca867
commit 44ecfa3
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diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
@@ -3,11 +3,6 @@
 ccflags-y += -I $(srctree)/arch/x86/kvm
 ccflags-$(CONFIG_KVM_WERROR) += -Werror
 
-ifeq ($(CONFIG_FRAME_POINTER),y)
-OBJECT_FILES_NON_STANDARD_vmx/vmenter.o := y
-OBJECT_FILES_NON_STANDARD_svm/vmenter.o := y
-endif
-
 include $(srctree)/virt/kvm/Makefile.kvm
 
 kvm-y			+= x86.o emulate.o i8259.o irq.o lapic.o \

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
@@ -434,7 +434,7 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,
 	/* Avoid using vmalloc for smaller buffers. */
 	size = npages * sizeof(struct page *);
 	if (size > PAGE_SIZE)
-		pages = __vmalloc(size, GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+		pages = __vmalloc(size, GFP_KERNEL_ACCOUNT);
 	else
 		pages = kmalloc(size, GFP_KERNEL_ACCOUNT);
 

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
@@ -1503,6 +1503,11 @@ static void svm_vcpu_free(struct kvm_vcpu *vcpu)
 	__free_pages(virt_to_page(svm->msrpm), get_order(MSRPM_SIZE));
 }
 
+static struct sev_es_save_area *sev_es_host_save_area(struct svm_cpu_data *sd)
+{
+	return page_address(sd->save_area) + 0x400;
+}
+
 static void svm_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
@@ -1519,12 +1524,8 @@ static void svm_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
 	 * or subsequent vmload of host 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);
-
-		sev_es_prepare_switch_to_guest(hostsa);
-	}
+	if (sev_es_guest(vcpu->kvm))
+		sev_es_prepare_switch_to_guest(sev_es_host_save_area(sd));
 
 	if (tsc_scaling)
 		__svm_write_tsc_multiplier(vcpu->arch.tsc_scaling_ratio);
@@ -4101,14 +4102,16 @@ static fastpath_t svm_exit_handlers_fastpath(struct kvm_vcpu *vcpu)
 
 static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu, bool spec_ctrl_intercepted)
 {
+	struct svm_cpu_data *sd = per_cpu_ptr(&svm_data, vcpu->cpu);
 	struct vcpu_svm *svm = to_svm(vcpu);
 
 	guest_state_enter_irqoff();
 
 	amd_clear_divider();
 
 	if (sev_es_guest(vcpu->kvm))
-		__svm_sev_es_vcpu_run(svm, spec_ctrl_intercepted);
+		__svm_sev_es_vcpu_run(svm, spec_ctrl_intercepted,
+				      sev_es_host_save_area(sd));
 	else
 		__svm_vcpu_run(svm, spec_ctrl_intercepted);
 

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
@@ -698,7 +698,8 @@ struct page *snp_safe_alloc_page(struct kvm_vcpu *vcpu);
 
 /* vmenter.S */
 
-void __svm_sev_es_vcpu_run(struct vcpu_svm *svm, bool spec_ctrl_intercepted);
+void __svm_sev_es_vcpu_run(struct vcpu_svm *svm, bool spec_ctrl_intercepted,
+			   struct sev_es_save_area *hostsa);
 void __svm_vcpu_run(struct vcpu_svm *svm, bool spec_ctrl_intercepted);
 
 #define DEFINE_KVM_GHCB_ACCESSORS(field)						\

diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S
@@ -3,6 +3,7 @@
 #include <asm/asm.h>
 #include <asm/asm-offsets.h>
 #include <asm/bitsperlong.h>
+#include <asm/frame.h>
 #include <asm/kvm_vcpu_regs.h>
 #include <asm/nospec-branch.h>
 #include "kvm-asm-offsets.h"
@@ -67,7 +68,7 @@
 		"", X86_FEATURE_V_SPEC_CTRL
 901:
 .endm
-.macro RESTORE_HOST_SPEC_CTRL_BODY
+.macro RESTORE_HOST_SPEC_CTRL_BODY spec_ctrl_intercepted:req
 900:
 	/* Same for after vmexit.  */
 	mov $MSR_IA32_SPEC_CTRL, %ecx
@@ -76,7 +77,7 @@
 	 * Load the value that the guest had written into MSR_IA32_SPEC_CTRL,
 	 * if it was not intercepted during guest execution.
 	 */
-	cmpb $0, (%_ASM_SP)
+	cmpb $0, \spec_ctrl_intercepted
 	jnz 998f
 	rdmsr
 	movl %eax, SVM_spec_ctrl(%_ASM_DI)
@@ -99,6 +100,7 @@
  */
 SYM_FUNC_START(__svm_vcpu_run)
 	push %_ASM_BP
+	mov  %_ASM_SP, %_ASM_BP
 #ifdef CONFIG_X86_64
 	push %r15
 	push %r14
@@ -268,7 +270,7 @@ SYM_FUNC_START(__svm_vcpu_run)
 	RET
 
 	RESTORE_GUEST_SPEC_CTRL_BODY
-	RESTORE_HOST_SPEC_CTRL_BODY
+	RESTORE_HOST_SPEC_CTRL_BODY (%_ASM_SP)
 
 10:	cmpb $0, _ASM_RIP(kvm_rebooting)
 	jne 2b
@@ -290,66 +292,68 @@ SYM_FUNC_START(__svm_vcpu_run)
 
 SYM_FUNC_END(__svm_vcpu_run)
 
+#ifdef CONFIG_KVM_AMD_SEV
+
+
+#ifdef CONFIG_X86_64
+#define SEV_ES_GPRS_BASE 0x300
+#define SEV_ES_RBX	(SEV_ES_GPRS_BASE + __VCPU_REGS_RBX * WORD_SIZE)
+#define SEV_ES_RBP	(SEV_ES_GPRS_BASE + __VCPU_REGS_RBP * WORD_SIZE)
+#define SEV_ES_RSI	(SEV_ES_GPRS_BASE + __VCPU_REGS_RSI * WORD_SIZE)
+#define SEV_ES_RDI	(SEV_ES_GPRS_BASE + __VCPU_REGS_RDI * WORD_SIZE)
+#define SEV_ES_R12	(SEV_ES_GPRS_BASE + __VCPU_REGS_R12 * WORD_SIZE)
+#define SEV_ES_R13	(SEV_ES_GPRS_BASE + __VCPU_REGS_R13 * WORD_SIZE)
+#define SEV_ES_R14	(SEV_ES_GPRS_BASE + __VCPU_REGS_R14 * WORD_SIZE)
+#define SEV_ES_R15	(SEV_ES_GPRS_BASE + __VCPU_REGS_R15 * WORD_SIZE)
+#endif
+
 /**
  * __svm_sev_es_vcpu_run - Run a SEV-ES vCPU via a transition to SVM guest mode
  * @svm:	struct vcpu_svm *
  * @spec_ctrl_intercepted: bool
  */
 SYM_FUNC_START(__svm_sev_es_vcpu_run)
-	push %_ASM_BP
-#ifdef CONFIG_X86_64
-	push %r15
-	push %r14
-	push %r13
-	push %r12
-#else
-	push %edi
-	push %esi
-#endif
-	push %_ASM_BX
+	FRAME_BEGIN
 
 	/*
-	 * Save variables needed after vmexit on the stack, in inverse
-	 * order compared to when they are needed.
+	 * Save non-volatile (callee-saved) registers to the host save area.
+	 * Except for RAX and RSP, all GPRs are restored on #VMEXIT, but not
+	 * saved on VMRUN.
 	 */
+	mov %rbp, SEV_ES_RBP (%rdx)
+	mov %r15, SEV_ES_R15 (%rdx)
+	mov %r14, SEV_ES_R14 (%rdx)
+	mov %r13, SEV_ES_R13 (%rdx)
+	mov %r12, SEV_ES_R12 (%rdx)
+	mov %rbx, SEV_ES_RBX (%rdx)
 
-	/* Accessed directly from the stack in RESTORE_HOST_SPEC_CTRL.  */
-	push %_ASM_ARG2
-
-	/* Save @svm. */
-	push %_ASM_ARG1
-
-.ifnc _ASM_ARG1, _ASM_DI
 	/*
-	 * Stash @svm in RDI early. On 32-bit, arguments are in RAX, RCX
-	 * and RDX which are clobbered by RESTORE_GUEST_SPEC_CTRL.
+	 * Save volatile registers that hold arguments that are needed after
+	 * #VMEXIT (RDI=@svm and RSI=@spec_ctrl_intercepted).
 	 */
-	mov %_ASM_ARG1, %_ASM_DI
-.endif
+	mov %rdi, SEV_ES_RDI (%rdx)
+	mov %rsi, SEV_ES_RSI (%rdx)
 
-	/* Clobbers RAX, RCX, RDX.  */
+	/* Clobbers RAX, RCX, RDX (@hostsa). */
 	RESTORE_GUEST_SPEC_CTRL
 
 	/* Get svm->current_vmcb->pa into RAX. */
-	mov SVM_current_vmcb(%_ASM_DI), %_ASM_AX
-	mov KVM_VMCB_pa(%_ASM_AX), %_ASM_AX
+	mov SVM_current_vmcb(%rdi), %rax
+	mov KVM_VMCB_pa(%rax), %rax
 
 	/* Enter guest mode */
 	sti
 
-1:	vmrun %_ASM_AX
+1:	vmrun %rax
 
 2:	cli
 
-	/* Pop @svm to RDI, guest registers have been saved already. */
-	pop %_ASM_DI
-
 #ifdef CONFIG_MITIGATION_RETPOLINE
 	/* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */
-	FILL_RETURN_BUFFER %_ASM_AX, RSB_CLEAR_LOOPS, X86_FEATURE_RETPOLINE
+	FILL_RETURN_BUFFER %rax, RSB_CLEAR_LOOPS, X86_FEATURE_RETPOLINE
 #endif
 
-	/* Clobbers RAX, RCX, RDX.  */
+	/* Clobbers RAX, RCX, RDX, consumes RDI (@svm) and RSI (@spec_ctrl_intercepted). */
 	RESTORE_HOST_SPEC_CTRL
 
 	/*
@@ -361,30 +365,17 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run)
 	 */
 	UNTRAIN_RET_VM
 
-	/* "Pop" @spec_ctrl_intercepted.  */
-	pop %_ASM_BX
-
-	pop %_ASM_BX
-
-#ifdef CONFIG_X86_64
-	pop %r12
-	pop %r13
-	pop %r14
-	pop %r15
-#else
-	pop %esi
-	pop %edi
-#endif
-	pop %_ASM_BP
+	FRAME_END
 	RET
 
 	RESTORE_GUEST_SPEC_CTRL_BODY
-	RESTORE_HOST_SPEC_CTRL_BODY
+	RESTORE_HOST_SPEC_CTRL_BODY %sil
 
-3:	cmpb $0, _ASM_RIP(kvm_rebooting)
+3:	cmpb $0, kvm_rebooting(%rip)
 	jne 2b
 	ud2
 
 	_ASM_EXTABLE(1b, 3b)
 
 SYM_FUNC_END(__svm_sev_es_vcpu_run)
+#endif /* CONFIG_KVM_AMD_SEV */