* [PATCH v2 1/5] objtool: KVM: x86: Check kvm_rebooting in kvm_spurious_fault()
2019-07-19 20:41 [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling Sean Christopherson
@ 2019-07-19 20:41 ` Sean Christopherson
2019-07-19 20:41 ` [PATCH v2 2/5] KVM: VMX: Optimize VMX instruction error and fault handling Sean Christopherson
` (5 subsequent siblings)
6 siblings, 0 replies; 11+ messages in thread
From: Sean Christopherson @ 2019-07-19 20:41 UTC (permalink / raw)
To: Paolo Bonzini, Radim Krčmář,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
Josh Poimboeuf, Peter Zijlstra
Cc: H. Peter Anvin, kvm, linux-kernel
Explicitly check kvm_reboot in kvm_spurious_fault() prior to invoking
BUG(), as opposed to assuming the caller has already done so. Letting
kvm_spurious_fault() be called "directly" will allow VMX to better
optimize its low level assembly flows.
As a happy side effect, kvm_spurious_fault() no longer needs to be
marked as a dead end since it doesn't unconditionally BUG().
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/include/asm/kvm_host.h | 2 +-
arch/x86/kvm/x86.c | 3 ++-
tools/objtool/check.c | 1 -
3 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 8282b8d41209..9739ed615faf 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1496,7 +1496,7 @@ enum {
#define kvm_arch_vcpu_memslots_id(vcpu) ((vcpu)->arch.hflags & HF_SMM_MASK ? 1 : 0)
#define kvm_memslots_for_spte_role(kvm, role) __kvm_memslots(kvm, (role).smm)
-asmlinkage void __noreturn kvm_spurious_fault(void);
+asmlinkage void kvm_spurious_fault(void);
/*
* Hardware virtualization extension instructions may fault if a
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4a0b74ecd1de..6bc012afb86a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -356,7 +356,8 @@ EXPORT_SYMBOL_GPL(kvm_set_apic_base);
asmlinkage __visible void kvm_spurious_fault(void)
{
/* Fault while not rebooting. We want the trace. */
- BUG();
+ if (!kvm_rebooting)
+ BUG();
}
EXPORT_SYMBOL_GPL(kvm_spurious_fault);
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 5f26620f13f5..688a9af8124d 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -138,7 +138,6 @@ static bool __dead_end_function(struct objtool_file *file, struct symbol *func,
"do_task_dead",
"__module_put_and_exit",
"complete_and_exit",
- "kvm_spurious_fault",
"__reiserfs_panic",
"lbug_with_loc",
"fortify_panic",
--
2.22.0
^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH v2 2/5] KVM: VMX: Optimize VMX instruction error and fault handling
2019-07-19 20:41 [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling Sean Christopherson
2019-07-19 20:41 ` [PATCH v2 1/5] objtool: KVM: x86: Check kvm_rebooting in kvm_spurious_fault() Sean Christopherson
@ 2019-07-19 20:41 ` Sean Christopherson
2019-07-19 20:41 ` [PATCH v2 3/5] KVM: VMX: Add error handling to VMREAD helper Sean Christopherson
` (4 subsequent siblings)
6 siblings, 0 replies; 11+ messages in thread
From: Sean Christopherson @ 2019-07-19 20:41 UTC (permalink / raw)
To: Paolo Bonzini, Radim Krčmář,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
Josh Poimboeuf, Peter Zijlstra
Cc: H. Peter Anvin, kvm, linux-kernel
Rework the VMX instruction helpers using asm-goto to branch directly
to error/fault "handlers" in lieu of using __ex(), i.e. the generic
____kvm_handle_fault_on_reboot(). Branching directly to fault handling
code during fixup avoids the extra JMP that is inserted after every VMX
instruction when using the generic "fault on reboot" (see commit
3901336ed9887, "x86/kvm: Don't call kvm_spurious_fault() from .fixup").
Opportunistically clean up the helpers so that they all have consistent
error handling and messages.
Leave the usage of ____kvm_handle_fault_on_reboot() (via __ex()) in
kvm_cpu_vmxoff() and nested_vmx_check_vmentry_hw() as is. The VMXOFF
case is not a fast path, i.e. the cleanliness of __ex() is worth the
JMP, and the extra JMP in nested_vmx_check_vmentry_hw() is unavoidable.
Note, VMREAD cannot get the asm-goto treatment as output operands aren't
compatible with GCC's asm-goto due to internal compiler restrictions.
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/vmx/ops.h | 72 +++++++++++++++++++++++-------------------
arch/x86/kvm/vmx/vmx.c | 34 ++++++++++++++++++++
2 files changed, 74 insertions(+), 32 deletions(-)
diff --git a/arch/x86/kvm/vmx/ops.h b/arch/x86/kvm/vmx/ops.h
index 2200fb698dd0..79e25d49d4d9 100644
--- a/arch/x86/kvm/vmx/ops.h
+++ b/arch/x86/kvm/vmx/ops.h
@@ -14,6 +14,12 @@
#define __ex_clear(x, reg) \
____kvm_handle_fault_on_reboot(x, "xor " reg ", " reg)
+void vmwrite_error(unsigned long field, unsigned long value);
+void vmclear_error(struct vmcs *vmcs, u64 phys_addr);
+void vmptrld_error(struct vmcs *vmcs, u64 phys_addr);
+void invvpid_error(unsigned long ext, u16 vpid, gva_t gva);
+void invept_error(unsigned long ext, u64 eptp, gpa_t gpa);
+
static __always_inline void vmcs_check16(unsigned long field)
{
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2000,
@@ -103,21 +109,39 @@ static __always_inline unsigned long vmcs_readl(unsigned long field)
return __vmcs_readl(field);
}
-static noinline void vmwrite_error(unsigned long field, unsigned long value)
-{
- printk(KERN_ERR "vmwrite error: reg %lx value %lx (err %d)\n",
- field, value, vmcs_read32(VM_INSTRUCTION_ERROR));
- dump_stack();
-}
+#define vmx_asm1(insn, op1, error_args...) \
+do { \
+ asm_volatile_goto("1: " __stringify(insn) " %0\n\t" \
+ ".byte 0x2e\n\t" /* branch not taken hint */ \
+ "jna %l[error]\n\t" \
+ _ASM_EXTABLE(1b, %l[fault]) \
+ : : op1 : "cc" : error, fault); \
+ return; \
+error: \
+ insn##_error(error_args); \
+ return; \
+fault: \
+ kvm_spurious_fault(); \
+} while (0)
+
+#define vmx_asm2(insn, op1, op2, error_args...) \
+do { \
+ asm_volatile_goto("1: " __stringify(insn) " %1, %0\n\t" \
+ ".byte 0x2e\n\t" /* branch not taken hint */ \
+ "jna %l[error]\n\t" \
+ _ASM_EXTABLE(1b, %l[fault]) \
+ : : op1, op2 : "cc" : error, fault); \
+ return; \
+error: \
+ insn##_error(error_args); \
+ return; \
+fault: \
+ kvm_spurious_fault(); \
+} while (0)
static __always_inline void __vmcs_writel(unsigned long field, unsigned long value)
{
- bool error;
-
- asm volatile (__ex("vmwrite %2, %1") CC_SET(na)
- : CC_OUT(na) (error) : "r"(field), "rm"(value));
- if (unlikely(error))
- vmwrite_error(field, value);
+ vmx_asm2(vmwrite, "r"(field), "rm"(value), field, value);
}
static __always_inline void vmcs_write16(unsigned long field, u16 value)
@@ -182,28 +206,18 @@ static __always_inline void vmcs_set_bits(unsigned long field, u32 mask)
static inline void vmcs_clear(struct vmcs *vmcs)
{
u64 phys_addr = __pa(vmcs);
- bool error;
- asm volatile (__ex("vmclear %1") CC_SET(na)
- : CC_OUT(na) (error) : "m"(phys_addr));
- if (unlikely(error))
- printk(KERN_ERR "kvm: vmclear fail: %p/%llx\n",
- vmcs, phys_addr);
+ vmx_asm1(vmclear, "m"(phys_addr), vmcs, phys_addr);
}
static inline void vmcs_load(struct vmcs *vmcs)
{
u64 phys_addr = __pa(vmcs);
- bool error;
if (static_branch_unlikely(&enable_evmcs))
return evmcs_load(phys_addr);
- asm volatile (__ex("vmptrld %1") CC_SET(na)
- : CC_OUT(na) (error) : "m"(phys_addr));
- if (unlikely(error))
- printk(KERN_ERR "kvm: vmptrld %p/%llx failed\n",
- vmcs, phys_addr);
+ vmx_asm1(vmptrld, "m"(phys_addr), vmcs, phys_addr);
}
static inline void __invvpid(unsigned long ext, u16 vpid, gva_t gva)
@@ -213,11 +227,8 @@ static inline void __invvpid(unsigned long ext, u16 vpid, gva_t gva)
u64 rsvd : 48;
u64 gva;
} operand = { vpid, 0, gva };
- bool error;
- asm volatile (__ex("invvpid %2, %1") CC_SET(na)
- : CC_OUT(na) (error) : "r"(ext), "m"(operand));
- BUG_ON(error);
+ vmx_asm2(invvpid, "r"(ext), "m"(operand), ext, vpid, gva);
}
static inline void __invept(unsigned long ext, u64 eptp, gpa_t gpa)
@@ -225,11 +236,8 @@ static inline void __invept(unsigned long ext, u64 eptp, gpa_t gpa)
struct {
u64 eptp, gpa;
} operand = {eptp, gpa};
- bool error;
- asm volatile (__ex("invept %2, %1") CC_SET(na)
- : CC_OUT(na) (error) : "r"(ext), "m"(operand));
- BUG_ON(error);
+ vmx_asm2(invept, "r"(ext), "m"(operand), ext, eptp, gpa);
}
static inline bool vpid_sync_vcpu_addr(int vpid, gva_t addr)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 69536553446d..46689019ebf7 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -343,6 +343,40 @@ static __always_inline void vmx_disable_intercept_for_msr(unsigned long *msr_bit
void vmx_vmexit(void);
+#define vmx_insn_failed(fmt...) \
+do { \
+ WARN_ONCE(1, fmt); \
+ pr_warn_ratelimited(fmt); \
+} while (0)
+
+noinline void vmwrite_error(unsigned long field, unsigned long value)
+{
+ vmx_insn_failed("kvm: vmwrite failed: field=%lx val=%lx err=%d\n",
+ field, value, vmcs_read32(VM_INSTRUCTION_ERROR));
+}
+
+noinline void vmclear_error(struct vmcs *vmcs, u64 phys_addr)
+{
+ vmx_insn_failed("kvm: vmclear failed: %p/%llx\n", vmcs, phys_addr);
+}
+
+noinline void vmptrld_error(struct vmcs *vmcs, u64 phys_addr)
+{
+ vmx_insn_failed("kvm: vmptrld failed: %p/%llx\n", vmcs, phys_addr);
+}
+
+noinline void invvpid_error(unsigned long ext, u16 vpid, gva_t gva)
+{
+ vmx_insn_failed("kvm: invvpid failed: ext=0x%lx vpid=%u gva=0x%lx\n",
+ ext, vpid, gva);
+}
+
+noinline void invept_error(unsigned long ext, u64 eptp, gpa_t gpa)
+{
+ vmx_insn_failed("kvm: invept failed: ext=0x%lx eptp=%llx gpa=0x%llx\n",
+ ext, eptp, gpa);
+}
+
static DEFINE_PER_CPU(struct vmcs *, vmxarea);
DEFINE_PER_CPU(struct vmcs *, current_vmcs);
/*
--
2.22.0
^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH v2 3/5] KVM: VMX: Add error handling to VMREAD helper
2019-07-19 20:41 [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling Sean Christopherson
2019-07-19 20:41 ` [PATCH v2 1/5] objtool: KVM: x86: Check kvm_rebooting in kvm_spurious_fault() Sean Christopherson
2019-07-19 20:41 ` [PATCH v2 2/5] KVM: VMX: Optimize VMX instruction error and fault handling Sean Christopherson
@ 2019-07-19 20:41 ` Sean Christopherson
2019-07-28 19:36 ` Josh Poimboeuf
2019-07-19 20:41 ` [PATCH v2 4/5] KVM: x86: Drop ____kvm_handle_fault_on_reboot() Sean Christopherson
` (3 subsequent siblings)
6 siblings, 1 reply; 11+ messages in thread
From: Sean Christopherson @ 2019-07-19 20:41 UTC (permalink / raw)
To: Paolo Bonzini, Radim Krčmář,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
Josh Poimboeuf, Peter Zijlstra
Cc: H. Peter Anvin, kvm, linux-kernel
Now that VMREAD flows require a taken branch, courtesy of commit
3901336ed9887 ("x86/kvm: Don't call kvm_spurious_fault() from .fixup")
bite the bullet and add full error handling to VMREAD, i.e. replace the
JMP added by __ex()/____kvm_handle_fault_on_reboot() with a hinted Jcc.
To minimize the code footprint, add a helper function, vmread_error(),
to handle both faults and failures so that the inline flow has a single
CALL.
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/vmx/ops.h | 21 +++++++++++++++++----
arch/x86/kvm/vmx/vmx.c | 8 ++++++++
2 files changed, 25 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/vmx/ops.h b/arch/x86/kvm/vmx/ops.h
index 79e25d49d4d9..45eaedee2ac0 100644
--- a/arch/x86/kvm/vmx/ops.h
+++ b/arch/x86/kvm/vmx/ops.h
@@ -11,9 +11,8 @@
#include "vmcs.h"
#define __ex(x) __kvm_handle_fault_on_reboot(x)
-#define __ex_clear(x, reg) \
- ____kvm_handle_fault_on_reboot(x, "xor " reg ", " reg)
+asmlinkage void vmread_error(unsigned long field, bool fault);
void vmwrite_error(unsigned long field, unsigned long value);
void vmclear_error(struct vmcs *vmcs, u64 phys_addr);
void vmptrld_error(struct vmcs *vmcs, u64 phys_addr);
@@ -68,8 +67,22 @@ static __always_inline unsigned long __vmcs_readl(unsigned long field)
{
unsigned long value;
- asm volatile (__ex_clear("vmread %1, %0", "%k0")
- : "=r"(value) : "r"(field));
+ asm volatile("1: vmread %2, %1\n\t"
+ ".byte 0x3e\n\t" /* branch taken hint */
+ "ja 3f\n\t"
+ "mov %2, %%" _ASM_ARG1 "\n\t"
+ "xor %%" _ASM_ARG2 ", %%" _ASM_ARG2 "\n\t"
+ "2: call vmread_error\n\t"
+ "xor %k1, %k1\n\t"
+ "3:\n\t"
+
+ ".pushsection .fixup, \"ax\"\n\t"
+ "4: mov %2, %%" _ASM_ARG1 "\n\t"
+ "mov $1, %%" _ASM_ARG2 "\n\t"
+ "jmp 2b\n\t"
+ ".popsection\n\t"
+ _ASM_EXTABLE(1b, 4b)
+ : ASM_CALL_CONSTRAINT, "=r"(value) : "r"(field) : "cc");
return value;
}
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 46689019ebf7..9acf3d6395d3 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -349,6 +349,14 @@ do { \
pr_warn_ratelimited(fmt); \
} while (0)
+asmlinkage void vmread_error(unsigned long field, bool fault)
+{
+ if (fault)
+ kvm_spurious_fault();
+ else
+ vmx_insn_failed("kvm: vmread failed: field=%lx\n", field);
+}
+
noinline void vmwrite_error(unsigned long field, unsigned long value)
{
vmx_insn_failed("kvm: vmwrite failed: field=%lx val=%lx err=%d\n",
--
2.22.0
^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH v2 3/5] KVM: VMX: Add error handling to VMREAD helper
2019-07-19 20:41 ` [PATCH v2 3/5] KVM: VMX: Add error handling to VMREAD helper Sean Christopherson
@ 2019-07-28 19:36 ` Josh Poimboeuf
2019-07-29 9:20 ` Paolo Bonzini
0 siblings, 1 reply; 11+ messages in thread
From: Josh Poimboeuf @ 2019-07-28 19:36 UTC (permalink / raw)
To: Sean Christopherson
Cc: Paolo Bonzini, Radim Krčmář,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
Peter Zijlstra, H. Peter Anvin, kvm, linux-kernel
On Fri, Jul 19, 2019 at 01:41:08PM -0700, Sean Christopherson wrote:
> @@ -68,8 +67,22 @@ static __always_inline unsigned long __vmcs_readl(unsigned long field)
> {
> unsigned long value;
>
> - asm volatile (__ex_clear("vmread %1, %0", "%k0")
> - : "=r"(value) : "r"(field));
> + asm volatile("1: vmread %2, %1\n\t"
> + ".byte 0x3e\n\t" /* branch taken hint */
> + "ja 3f\n\t"
> + "mov %2, %%" _ASM_ARG1 "\n\t"
> + "xor %%" _ASM_ARG2 ", %%" _ASM_ARG2 "\n\t"
> + "2: call vmread_error\n\t"
> + "xor %k1, %k1\n\t"
> + "3:\n\t"
> +
> + ".pushsection .fixup, \"ax\"\n\t"
> + "4: mov %2, %%" _ASM_ARG1 "\n\t"
> + "mov $1, %%" _ASM_ARG2 "\n\t"
> + "jmp 2b\n\t"
> + ".popsection\n\t"
> + _ASM_EXTABLE(1b, 4b)
> + : ASM_CALL_CONSTRAINT, "=r"(value) : "r"(field) : "cc");
Was there a reason you didn't do the asm goto thing here like you did
for the previous patch? That seemed cleaner, and needs less asm.
I think the branch hints aren't needed -- they're ignored on modern
processors. Ditto for the previous patch.
Also please use named asm operands whereever you can, like "%[field]"
instead of "%2". It helps a lot with readability.
--
Josh
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v2 3/5] KVM: VMX: Add error handling to VMREAD helper
2019-07-28 19:36 ` Josh Poimboeuf
@ 2019-07-29 9:20 ` Paolo Bonzini
0 siblings, 0 replies; 11+ messages in thread
From: Paolo Bonzini @ 2019-07-29 9:20 UTC (permalink / raw)
To: Josh Poimboeuf, Sean Christopherson
Cc: Radim Krčmář,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
Peter Zijlstra, H. Peter Anvin, kvm, linux-kernel
On 28/07/19 21:36, Josh Poimboeuf wrote:
> On Fri, Jul 19, 2019 at 01:41:08PM -0700, Sean Christopherson wrote:
>> @@ -68,8 +67,22 @@ static __always_inline unsigned long __vmcs_readl(unsigned long field)
>> {
>> unsigned long value;
>>
>> - asm volatile (__ex_clear("vmread %1, %0", "%k0")
>> - : "=r"(value) : "r"(field));
>> + asm volatile("1: vmread %2, %1\n\t"
>> + ".byte 0x3e\n\t" /* branch taken hint */
>> + "ja 3f\n\t"
>> + "mov %2, %%" _ASM_ARG1 "\n\t"
>> + "xor %%" _ASM_ARG2 ", %%" _ASM_ARG2 "\n\t"
>> + "2: call vmread_error\n\t"
>> + "xor %k1, %k1\n\t"
>> + "3:\n\t"
>> +
>> + ".pushsection .fixup, \"ax\"\n\t"
>> + "4: mov %2, %%" _ASM_ARG1 "\n\t"
>> + "mov $1, %%" _ASM_ARG2 "\n\t"
>> + "jmp 2b\n\t"
>> + ".popsection\n\t"
>> + _ASM_EXTABLE(1b, 4b)
>> + : ASM_CALL_CONSTRAINT, "=r"(value) : "r"(field) : "cc");
>
> Was there a reason you didn't do the asm goto thing here like you did
> for the previous patch? That seemed cleaner, and needs less asm.
It's because asm goto doesn't support outputs.
Paolo
> I think the branch hints aren't needed -- they're ignored on modern
> processors. Ditto for the previous patch.
>
> Also please use named asm operands whereever you can, like "%[field]"
> instead of "%2". It helps a lot with readability.
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* [PATCH v2 4/5] KVM: x86: Drop ____kvm_handle_fault_on_reboot()
2019-07-19 20:41 [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling Sean Christopherson
` (2 preceding siblings ...)
2019-07-19 20:41 ` [PATCH v2 3/5] KVM: VMX: Add error handling to VMREAD helper Sean Christopherson
@ 2019-07-19 20:41 ` Sean Christopherson
2019-07-19 20:41 ` [PATCH v2 5/5] KVM: x86: Don't check kvm_rebooting in __kvm_handle_fault_on_reboot() Sean Christopherson
` (2 subsequent siblings)
6 siblings, 0 replies; 11+ messages in thread
From: Sean Christopherson @ 2019-07-19 20:41 UTC (permalink / raw)
To: Paolo Bonzini, Radim Krčmář,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
Josh Poimboeuf, Peter Zijlstra
Cc: H. Peter Anvin, kvm, linux-kernel
Remove the variation of __kvm_handle_fault_on_reboot() that accepts a
post-fault cleanup instruction now that its sole user (VMREAD) uses
a different method for handling faults.
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/include/asm/kvm_host.h | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 9739ed615faf..92c59cd923b6 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1504,7 +1504,7 @@ asmlinkage void kvm_spurious_fault(void);
* Usually after catching the fault we just panic; during reboot
* instead the instruction is ignored.
*/
-#define ____kvm_handle_fault_on_reboot(insn, cleanup_insn) \
+#define __kvm_handle_fault_on_reboot(insn) \
"666: \n\t" \
insn "\n\t" \
"jmp 668f \n\t" \
@@ -1513,16 +1513,12 @@ asmlinkage void kvm_spurious_fault(void);
"668: \n\t" \
".pushsection .fixup, \"ax\" \n\t" \
"700: \n\t" \
- cleanup_insn "\n\t" \
"cmpb $0, kvm_rebooting\n\t" \
"je 667b \n\t" \
"jmp 668b \n\t" \
".popsection \n\t" \
_ASM_EXTABLE(666b, 700b)
-#define __kvm_handle_fault_on_reboot(insn) \
- ____kvm_handle_fault_on_reboot(insn, "")
-
#define KVM_ARCH_WANT_MMU_NOTIFIER
int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end);
int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end);
--
2.22.0
^ permalink raw reply related [flat|nested] 11+ messages in thread
* [PATCH v2 5/5] KVM: x86: Don't check kvm_rebooting in __kvm_handle_fault_on_reboot()
2019-07-19 20:41 [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling Sean Christopherson
` (3 preceding siblings ...)
2019-07-19 20:41 ` [PATCH v2 4/5] KVM: x86: Drop ____kvm_handle_fault_on_reboot() Sean Christopherson
@ 2019-07-19 20:41 ` Sean Christopherson
2019-07-19 21:41 ` Paolo Bonzini
2019-09-24 21:03 ` [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling Sean Christopherson
2019-09-25 13:30 ` Paolo Bonzini
6 siblings, 1 reply; 11+ messages in thread
From: Sean Christopherson @ 2019-07-19 20:41 UTC (permalink / raw)
To: Paolo Bonzini, Radim Krčmář,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
Josh Poimboeuf, Peter Zijlstra
Cc: H. Peter Anvin, kvm, linux-kernel
Remove the kvm_rebooting check from VMX/SVM instruction exception fixup
now that kvm_spurious_fault() conditions its BUG() on !kvm_rebooting.
Because the 'cleanup_insn' functionally is also gone, deferring to
kvm_spurious_fault() means __kvm_handle_fault_on_reboot() can eliminate
its .fixup code entirely and have its exception table entry branch
directly to the call to kvm_spurious_fault().
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/include/asm/kvm_host.h | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 92c59cd923b6..a5ae5562ce0a 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1511,13 +1511,7 @@ asmlinkage void kvm_spurious_fault(void);
"667: \n\t" \
"call kvm_spurious_fault \n\t" \
"668: \n\t" \
- ".pushsection .fixup, \"ax\" \n\t" \
- "700: \n\t" \
- "cmpb $0, kvm_rebooting\n\t" \
- "je 667b \n\t" \
- "jmp 668b \n\t" \
- ".popsection \n\t" \
- _ASM_EXTABLE(666b, 700b)
+ _ASM_EXTABLE(666b, 667b)
#define KVM_ARCH_WANT_MMU_NOTIFIER
int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end);
--
2.22.0
^ permalink raw reply related [flat|nested] 11+ messages in thread
* Re: [PATCH v2 5/5] KVM: x86: Don't check kvm_rebooting in __kvm_handle_fault_on_reboot()
2019-07-19 20:41 ` [PATCH v2 5/5] KVM: x86: Don't check kvm_rebooting in __kvm_handle_fault_on_reboot() Sean Christopherson
@ 2019-07-19 21:41 ` Paolo Bonzini
0 siblings, 0 replies; 11+ messages in thread
From: Paolo Bonzini @ 2019-07-19 21:41 UTC (permalink / raw)
To: Sean Christopherson, Radim Krčmář,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
Josh Poimboeuf, Peter Zijlstra
Cc: H. Peter Anvin, kvm, linux-kernel
On 19/07/19 22:41, Sean Christopherson wrote:
> Remove the kvm_rebooting check from VMX/SVM instruction exception fixup
> now that kvm_spurious_fault() conditions its BUG() on !kvm_rebooting.
> Because the 'cleanup_insn' functionally is also gone, deferring to
> kvm_spurious_fault() means __kvm_handle_fault_on_reboot() can eliminate
> its .fixup code entirely and have its exception table entry branch
> directly to the call to kvm_spurious_fault().
>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Josh Poimboeuf <jpoimboe@redhat.com>
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
> arch/x86/include/asm/kvm_host.h | 8 +-------
> 1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 92c59cd923b6..a5ae5562ce0a 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1511,13 +1511,7 @@ asmlinkage void kvm_spurious_fault(void);
> "667: \n\t" \
> "call kvm_spurious_fault \n\t" \
> "668: \n\t" \
> - ".pushsection .fixup, \"ax\" \n\t" \
> - "700: \n\t" \
> - "cmpb $0, kvm_rebooting\n\t" \
> - "je 667b \n\t" \
> - "jmp 668b \n\t" \
> - ".popsection \n\t" \
> - _ASM_EXTABLE(666b, 700b)
> + _ASM_EXTABLE(666b, 667b)
>
> #define KVM_ARCH_WANT_MMU_NOTIFIER
> int kvm_unmap_hva_range(struct kvm *kvm, unsigned long start, unsigned long end);
>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling
2019-07-19 20:41 [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling Sean Christopherson
` (4 preceding siblings ...)
2019-07-19 20:41 ` [PATCH v2 5/5] KVM: x86: Don't check kvm_rebooting in __kvm_handle_fault_on_reboot() Sean Christopherson
@ 2019-09-24 21:03 ` Sean Christopherson
2019-09-25 13:30 ` Paolo Bonzini
6 siblings, 0 replies; 11+ messages in thread
From: Sean Christopherson @ 2019-09-24 21:03 UTC (permalink / raw)
To: Paolo Bonzini, Radim Krčmář,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
Josh Poimboeuf, Peter Zijlstra
Cc: H. Peter Anvin, kvm, linux-kernel
Paolo,
Any chance this can be picked up for 5.4? Josh's kvm_spurious_fault()
changes went into 5.3, so this can be taken through the KVM tree, which
probably makes the most sense since the non-KVM change is a one line
deletion.
On Fri, Jul 19, 2019 at 01:41:05PM -0700, Sean Christopherson wrote:
> A recent commit reworked __kvm_handle_fault_on_reboot() to play nice with
> objtool. An unfortunate side effect is that JMP is now inserted after
> most VMX instructions so that the reboot macro can use an actual CALL to
> kvm_spurious_fault() instead of a funky PUSH+JMP facsimile in .fixup.
>
> Rework the low level VMX instruction helpers to handle unexpected faults
> manually instead of relying on the "fault on reboot" macro. By using
> asm-goto, most helpers can branch directly to an in-function call to
> kvm_spurious_fault(), which can then be optimized by compilers to reside
> out-of-line at the end of the function instead of inline as done by
> "fault on reboot".
>
> The net impact relative to the current code base is more or less a nop
> when building with a compiler that supports __GCC_ASM_FLAG_OUTPUTS__.
> A bunch of code that was previously in .fixup gets moved into the slow
> paths of functions, but the fast paths are more basically unchanged.
>
> Without __GCC_ASM_FLAG_OUTPUTS__, manually coding the Jcc is a net
> positive as CC_SET() without compiler support almost always generates a
> SETcc+CMP+Jcc sequence, which is now replaced with a single Jcc.
>
> A small bonus is that the Jcc instrs are hinted to predict that the VMX
> instr will be successful.
>
> v2:
> - Rebased to x86/master, commit eceffd88ca20 ("Merge branch 'x86/urgent'")
> - Reworded changelogs to reference the commit instead lkml link for
> the recent changes to __kvm_handle_fault_on_reboot().
> - Added Paolo's acks for patch 1-4
> - Added patch 5 to do more cleanup, which was made possible by rebasing
> on top of the __kvm_handle_fault_on_reboot() changes.
>
> Sean Christopherson (5):
> objtool: KVM: x86: Check kvm_rebooting in kvm_spurious_fault()
> KVM: VMX: Optimize VMX instruction error and fault handling
> KVM: VMX: Add error handling to VMREAD helper
> KVM: x86: Drop ____kvm_handle_fault_on_reboot()
> KVM: x86: Don't check kvm_rebooting in __kvm_handle_fault_on_reboot()
>
> arch/x86/include/asm/kvm_host.h | 16 ++----
> arch/x86/kvm/vmx/ops.h | 93 ++++++++++++++++++++-------------
> arch/x86/kvm/vmx/vmx.c | 42 +++++++++++++++
> arch/x86/kvm/x86.c | 3 +-
> tools/objtool/check.c | 1 -
> 5 files changed, 104 insertions(+), 51 deletions(-)
>
> --
> 2.22.0
>
^ permalink raw reply [flat|nested] 11+ messages in thread
* Re: [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling
2019-07-19 20:41 [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling Sean Christopherson
` (5 preceding siblings ...)
2019-09-24 21:03 ` [PATCH v2 0/5] KVM: VMX: Optimize VMX instrs error/fault handling Sean Christopherson
@ 2019-09-25 13:30 ` Paolo Bonzini
6 siblings, 0 replies; 11+ messages in thread
From: Paolo Bonzini @ 2019-09-25 13:30 UTC (permalink / raw)
To: Sean Christopherson, Radim Krčmář,
Thomas Gleixner, Ingo Molnar, Borislav Petkov, x86,
Josh Poimboeuf, Peter Zijlstra
Cc: H. Peter Anvin, kvm, linux-kernel
On 19/07/19 22:41, Sean Christopherson wrote:
> A recent commit reworked __kvm_handle_fault_on_reboot() to play nice with
> objtool. An unfortunate side effect is that JMP is now inserted after
> most VMX instructions so that the reboot macro can use an actual CALL to
> kvm_spurious_fault() instead of a funky PUSH+JMP facsimile in .fixup.
>
> Rework the low level VMX instruction helpers to handle unexpected faults
> manually instead of relying on the "fault on reboot" macro. By using
> asm-goto, most helpers can branch directly to an in-function call to
> kvm_spurious_fault(), which can then be optimized by compilers to reside
> out-of-line at the end of the function instead of inline as done by
> "fault on reboot".
>
> The net impact relative to the current code base is more or less a nop
> when building with a compiler that supports __GCC_ASM_FLAG_OUTPUTS__.
> A bunch of code that was previously in .fixup gets moved into the slow
> paths of functions, but the fast paths are more basically unchanged.
>
> Without __GCC_ASM_FLAG_OUTPUTS__, manually coding the Jcc is a net
> positive as CC_SET() without compiler support almost always generates a
> SETcc+CMP+Jcc sequence, which is now replaced with a single Jcc.
>
> A small bonus is that the Jcc instrs are hinted to predict that the VMX
> instr will be successful.
>
> v2:
> - Rebased to x86/master, commit eceffd88ca20 ("Merge branch 'x86/urgent'")
> - Reworded changelogs to reference the commit instead lkml link for
> the recent changes to __kvm_handle_fault_on_reboot().
> - Added Paolo's acks for patch 1-4
> - Added patch 5 to do more cleanup, which was made possible by rebasing
> on top of the __kvm_handle_fault_on_reboot() changes.
>
> Sean Christopherson (5):
> objtool: KVM: x86: Check kvm_rebooting in kvm_spurious_fault()
> KVM: VMX: Optimize VMX instruction error and fault handling
> KVM: VMX: Add error handling to VMREAD helper
> KVM: x86: Drop ____kvm_handle_fault_on_reboot()
> KVM: x86: Don't check kvm_rebooting in __kvm_handle_fault_on_reboot()
>
> arch/x86/include/asm/kvm_host.h | 16 ++----
> arch/x86/kvm/vmx/ops.h | 93 ++++++++++++++++++++-------------
> arch/x86/kvm/vmx/vmx.c | 42 +++++++++++++++
> arch/x86/kvm/x86.c | 3 +-
> tools/objtool/check.c | 1 -
> 5 files changed, 104 insertions(+), 51 deletions(-)
>
Queued, thanks.
Paolo
^ permalink raw reply [flat|nested] 11+ messages in thread