[PATCH 1/2] KVM: VMX: Explicitly reference RCX as the vmx_vcpu pointer in asm blobs
Sultan Alsawaf
sultan.alsawaf at canonical.com
Thu May 28 19:56:02 UTC 2020
From: Sean Christopherson <sean.j.christopherson at intel.com>
BugLink: https://bugs.launchpad.net/bugs/1881072
commit 051a2d3e59e51ae49fd56aef34e472832897ce46 upstream.
Use '%% " _ASM_CX"' instead of '%0' to dereference RCX, i.e. the
'struct vcpu_vmx' pointer, in the VM-Enter asm blobs of vmx_vcpu_run()
and nested_vmx_check_vmentry_hw(). Using the symbolic name means that
adding/removing an output parameter(s) requires "rewriting" almost all
of the asm blob, which makes it nearly impossible to understand what's
being changed in even the most minor patches.
Opportunistically improve the code comments.
Signed-off-by: Sean Christopherson <sean.j.christopherson at intel.com>
Reviewed-by: Andi Kleen <ak at linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
(cherry picked from commit 0590bcdea7955384a1e8187c6898c31aa213b105)
Signed-off-by: Sultan Alsawaf <sultan.alsawaf at canonical.com>
---
arch/x86/kvm/vmx.c | 86 +++++++++++++++++++++++++---------------------
1 file changed, 47 insertions(+), 39 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 6875c8d13052..6542cdd4ff64 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -9783,38 +9783,39 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
"push %%" _ASM_DX "; push %%" _ASM_BP ";"
"push %%" _ASM_CX " \n\t" /* placeholder for guest rcx */
"push %%" _ASM_CX " \n\t"
- "cmp %%" _ASM_SP ", %c[host_rsp](%0) \n\t"
+ "cmp %%" _ASM_SP ", %c[host_rsp](%%" _ASM_CX ") \n\t"
"je 1f \n\t"
- "mov %%" _ASM_SP ", %c[host_rsp](%0) \n\t"
+ "mov %%" _ASM_SP ", %c[host_rsp](%%" _ASM_CX ") \n\t"
__ex(ASM_VMX_VMWRITE_RSP_RDX) "\n\t"
"1: \n\t"
/* Reload cr2 if changed */
- "mov %c[cr2](%0), %%" _ASM_AX " \n\t"
+ "mov %c[cr2](%%" _ASM_CX "), %%" _ASM_AX " \n\t"
"mov %%cr2, %%" _ASM_DX " \n\t"
"cmp %%" _ASM_AX ", %%" _ASM_DX " \n\t"
"je 2f \n\t"
"mov %%" _ASM_AX", %%cr2 \n\t"
"2: \n\t"
/* Check if vmlaunch of vmresume is needed */
- "cmpb $0, %c[launched](%0) \n\t"
+ "cmpb $0, %c[launched](%%" _ASM_CX ") \n\t"
/* Load guest registers. Don't clobber flags. */
- "mov %c[rax](%0), %%" _ASM_AX " \n\t"
- "mov %c[rbx](%0), %%" _ASM_BX " \n\t"
- "mov %c[rdx](%0), %%" _ASM_DX " \n\t"
- "mov %c[rsi](%0), %%" _ASM_SI " \n\t"
- "mov %c[rdi](%0), %%" _ASM_DI " \n\t"
- "mov %c[rbp](%0), %%" _ASM_BP " \n\t"
+ "mov %c[rax](%%" _ASM_CX "), %%" _ASM_AX " \n\t"
+ "mov %c[rbx](%%" _ASM_CX "), %%" _ASM_BX " \n\t"
+ "mov %c[rdx](%%" _ASM_CX "), %%" _ASM_DX " \n\t"
+ "mov %c[rsi](%%" _ASM_CX "), %%" _ASM_SI " \n\t"
+ "mov %c[rdi](%%" _ASM_CX "), %%" _ASM_DI " \n\t"
+ "mov %c[rbp](%%" _ASM_CX "), %%" _ASM_BP " \n\t"
#ifdef CONFIG_X86_64
- "mov %c[r8](%0), %%r8 \n\t"
- "mov %c[r9](%0), %%r9 \n\t"
- "mov %c[r10](%0), %%r10 \n\t"
- "mov %c[r11](%0), %%r11 \n\t"
- "mov %c[r12](%0), %%r12 \n\t"
- "mov %c[r13](%0), %%r13 \n\t"
- "mov %c[r14](%0), %%r14 \n\t"
- "mov %c[r15](%0), %%r15 \n\t"
+ "mov %c[r8](%%" _ASM_CX "), %%r8 \n\t"
+ "mov %c[r9](%%" _ASM_CX "), %%r9 \n\t"
+ "mov %c[r10](%%" _ASM_CX "), %%r10 \n\t"
+ "mov %c[r11](%%" _ASM_CX "), %%r11 \n\t"
+ "mov %c[r12](%%" _ASM_CX "), %%r12 \n\t"
+ "mov %c[r13](%%" _ASM_CX "), %%r13 \n\t"
+ "mov %c[r14](%%" _ASM_CX "), %%r14 \n\t"
+ "mov %c[r15](%%" _ASM_CX "), %%r15 \n\t"
#endif
- "mov %c[rcx](%0), %%" _ASM_CX " \n\t" /* kills %0 (ecx) */
+ /* Load guest RCX. This kills the vmx_vcpu pointer! */
+ "mov %c[rcx](%%" _ASM_CX "), %%" _ASM_CX " \n\t"
/* Enter guest mode */
"jne 1f \n\t"
@@ -9822,26 +9823,33 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
"jmp 2f \n\t"
"1: " __ex(ASM_VMX_VMRESUME) "\n\t"
"2: "
- /* Save guest registers, load host registers, keep flags */
- "mov %0, %c[wordsize](%%" _ASM_SP ") \n\t"
- "pop %0 \n\t"
- "setbe %c[fail](%0)\n\t"
- "mov %%" _ASM_AX ", %c[rax](%0) \n\t"
- "mov %%" _ASM_BX ", %c[rbx](%0) \n\t"
- __ASM_SIZE(pop) " %c[rcx](%0) \n\t"
- "mov %%" _ASM_DX ", %c[rdx](%0) \n\t"
- "mov %%" _ASM_SI ", %c[rsi](%0) \n\t"
- "mov %%" _ASM_DI ", %c[rdi](%0) \n\t"
- "mov %%" _ASM_BP ", %c[rbp](%0) \n\t"
+
+ /* Save guest's RCX to the stack placeholder (see above) */
+ "mov %%" _ASM_CX ", %c[wordsize](%%" _ASM_SP ") \n\t"
+
+ /* Load host's RCX, i.e. the vmx_vcpu pointer */
+ "pop %%" _ASM_CX " \n\t"
+
+ /* Set vmx->fail based on EFLAGS.{CF,ZF} */
+ "setbe %c[fail](%%" _ASM_CX ")\n\t"
+
+ /* Save all guest registers, including RCX from the stack */
+ "mov %%" _ASM_AX ", %c[rax](%%" _ASM_CX ") \n\t"
+ "mov %%" _ASM_BX ", %c[rbx](%%" _ASM_CX ") \n\t"
+ __ASM_SIZE(pop) " %c[rcx](%%" _ASM_CX ") \n\t"
+ "mov %%" _ASM_DX ", %c[rdx](%%" _ASM_CX ") \n\t"
+ "mov %%" _ASM_SI ", %c[rsi](%%" _ASM_CX ") \n\t"
+ "mov %%" _ASM_DI ", %c[rdi](%%" _ASM_CX ") \n\t"
+ "mov %%" _ASM_BP ", %c[rbp](%%" _ASM_CX ") \n\t"
#ifdef CONFIG_X86_64
- "mov %%r8, %c[r8](%0) \n\t"
- "mov %%r9, %c[r9](%0) \n\t"
- "mov %%r10, %c[r10](%0) \n\t"
- "mov %%r11, %c[r11](%0) \n\t"
- "mov %%r12, %c[r12](%0) \n\t"
- "mov %%r13, %c[r13](%0) \n\t"
- "mov %%r14, %c[r14](%0) \n\t"
- "mov %%r15, %c[r15](%0) \n\t"
+ "mov %%r8, %c[r8](%%" _ASM_CX ") \n\t"
+ "mov %%r9, %c[r9](%%" _ASM_CX ") \n\t"
+ "mov %%r10, %c[r10](%%" _ASM_CX ") \n\t"
+ "mov %%r11, %c[r11](%%" _ASM_CX ") \n\t"
+ "mov %%r12, %c[r12](%%" _ASM_CX ") \n\t"
+ "mov %%r13, %c[r13](%%" _ASM_CX ") \n\t"
+ "mov %%r14, %c[r14](%%" _ASM_CX ") \n\t"
+ "mov %%r15, %c[r15](%%" _ASM_CX ") \n\t"
/*
* Clear all general purpose registers (except RSP, which is loaded by
@@ -9861,7 +9869,7 @@ static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
"xor %%r15d, %%r15d \n\t"
#endif
"mov %%cr2, %%" _ASM_AX " \n\t"
- "mov %%" _ASM_AX ", %c[cr2](%0) \n\t"
+ "mov %%" _ASM_AX ", %c[cr2](%%" _ASM_CX ") \n\t"
"xor %%eax, %%eax \n\t"
"xor %%ebx, %%ebx \n\t"
--
2.20.1
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