From: Sean Christopherson <seanjc@google.com>
To: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
Tom Lendacky <thomas.lendacky@amd.com>,
Michael Roth <michael.roth@amd.com>,
Alexey Kardashevskiy <aik@amd.com>
Subject: [PATCH 6/8] KVM: SVM: Save/restore args across SEV-ES VMRUN via host save area
Date: Fri, 23 Feb 2024 12:42:31 -0800 [thread overview]
Message-ID: <20240223204233.3337324-7-seanjc@google.com> (raw)
In-Reply-To: <20240223204233.3337324-1-seanjc@google.com>
Use the host save area to preserve volatile registers that are used in
__svm_sev_es_vcpu_run() to access function parameters after #VMEXIT.
Like saving/restoring non-volatile registers, there's no reason not to
take advantage of hardware restoring registers on #VMEXIT, as doing so
shaves a few instructions and the save area is going to be accessed no
matter what.
Converting all register save/restore code to use the host save area also
make it easier to follow the SEV-ES VMRUN flow in its entirety, as
opposed to having a mix of stack-based versus host save area save/restore.
Add a parameter to RESTORE_HOST_SPEC_CTRL_BODY so that the SEV-ES path
doesn't need to write @spec_ctrl_intercepted to memory just to play nice
with the common macro.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/svm/vmenter.S | 29 +++++++++++++----------------
1 file changed, 13 insertions(+), 16 deletions(-)
diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S
index e92953427100..48cdba47622c 100644
--- a/arch/x86/kvm/svm/vmenter.S
+++ b/arch/x86/kvm/svm/vmenter.S
@@ -67,7 +67,7 @@
"", 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 +76,7 @@
* 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)
@@ -269,7 +269,7 @@ 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
@@ -298,6 +298,8 @@ SYM_FUNC_END(__svm_vcpu_run)
#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)
@@ -322,11 +324,12 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run)
mov %r12, SEV_ES_R12 (%rdx)
mov %rbx, SEV_ES_RBX (%rdx)
- /* Accessed directly from the stack in RESTORE_HOST_SPEC_CTRL. */
- push %rsi
-
- /* Save @svm. */
- push %rdi
+ /*
+ * Save volatile registers that hold arguments that are needed after
+ * #VMEXIT (RDI=@svm and RSI=@spec_ctrl_intercepted).
+ */
+ mov %rdi, SEV_ES_RDI (%rdx)
+ mov %rsi, SEV_ES_RSI (%rdx)
/* Clobbers RAX, RCX, RDX (@hostsa). */
RESTORE_GUEST_SPEC_CTRL
@@ -342,15 +345,12 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run)
2: cli
- /* Pop @svm to RDI, guest registers have been saved already. */
- pop %rdi
-
#ifdef CONFIG_RETPOLINE
/* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */
FILL_RETURN_BUFFER %rax, RSB_CLEAR_LOOPS, X86_FEATURE_RETPOLINE
#endif
- /* Clobbers RAX, RCX, RDX, consumes RDI (@svm). */
+ /* Clobbers RAX, RCX, RDX, consumes RDI (@svm) and RSI (@spec_ctrl_intercepted). */
RESTORE_HOST_SPEC_CTRL
/*
@@ -362,13 +362,10 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run)
*/
UNTRAIN_RET_VM
- /* "Pop" and discard @spec_ctrl_intercepted. */
- pop %rax
-
RET
RESTORE_GUEST_SPEC_CTRL_BODY
- RESTORE_HOST_SPEC_CTRL_BODY
+ RESTORE_HOST_SPEC_CTRL_BODY %sil
3: cmpb $0, kvm_rebooting(%rip)
jne 2b
--
2.44.0.rc0.258.g7320e95886-goog
next prev parent reply other threads:[~2024-02-23 20:42 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-23 20:42 [PATCH 0/8] KVM: SVM: Clean up VMRUN=>#VMEXIT assembly Sean Christopherson
2024-02-23 20:42 ` [PATCH 1/8] KVM: SVM: Create a stack frame in __svm_vcpu_run() for unwinding Sean Christopherson
2024-02-23 20:42 ` [PATCH 2/8] KVM: SVM: Wrap __svm_sev_es_vcpu_run() with #ifdef CONFIG_KVM_AMD_SEV Sean Christopherson
2024-02-23 20:42 ` [PATCH 3/8] KVM: SVM: Drop 32-bit "support" from __svm_sev_es_vcpu_run() Sean Christopherson
2024-02-23 20:42 ` [PATCH 4/8] KVM: SVM: Clobber RAX instead of RBX when discarding spec_ctrl_intercepted Sean Christopherson
2024-02-23 20:42 ` [PATCH 5/8] KVM: SVM: Save/restore non-volatile GPRs in SEV-ES VMRUN via host save area Sean Christopherson
2024-02-23 20:42 ` Sean Christopherson [this message]
2024-02-23 20:42 ` [PATCH 7/8] KVM: SVM: Create a stack frame in __svm_sev_es_vcpu_run() Sean Christopherson
2024-02-23 20:42 ` [PATCH 8/8] KVM: x86: Stop compiling vmenter.S with OBJECT_FILES_NON_STANDARD Sean Christopherson
2024-02-26 20:02 ` [PATCH 0/8] KVM: SVM: Clean up VMRUN=>#VMEXIT assembly Tom Lendacky
2024-04-10 0:19 ` Sean Christopherson
2024-04-17 12:58 ` Paolo Bonzini
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