linux/arch/x86/kvm/vmx/vmx_ops.h
Linus Torvalds 4356e9f841 work around gcc bugs with 'asm goto' with outputs
We've had issues with gcc and 'asm goto' before, and we created a
'asm_volatile_goto()' macro for that in the past: see commits
3f0116c323 ("compiler/gcc4: Add quirk for 'asm goto' miscompilation
bug") and a9f180345f ("compiler/gcc4: Make quirk for
asm_volatile_goto() unconditional").

Then, much later, we ended up removing the workaround in commit
43c249ea0b ("compiler-gcc.h: remove ancient workaround for gcc PR
58670") because we no longer supported building the kernel with the
affected gcc versions, but we left the macro uses around.

Now, Sean Christopherson reports a new version of a very similar
problem, which is fixed by re-applying that ancient workaround.  But the
problem in question is limited to only the 'asm goto with outputs'
cases, so instead of re-introducing the old workaround as-is, let's
rename and limit the workaround to just that much less common case.

It looks like there are at least two separate issues that all hit in
this area:

 (a) some versions of gcc don't mark the asm goto as 'volatile' when it
     has outputs:

        https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98619
        https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110420

     which is easy to work around by just adding the 'volatile' by hand.

 (b) Internal compiler errors:

        https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110422

     which are worked around by adding the extra empty 'asm' as a
     barrier, as in the original workaround.

but the problem Sean sees may be a third thing since it involves bad
code generation (not an ICE) even with the manually added 'volatile'.

but the same old workaround works for this case, even if this feels a
bit like voodoo programming and may only be hiding the issue.

Reported-and-tested-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/all/20240208220604.140859-1-seanjc@google.com/
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: Jakub Jelinek <jakub@redhat.com>
Cc: Andrew Pinski <quic_apinski@quicinc.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2024-02-09 15:57:48 -08:00

370 lines
10 KiB
C

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __KVM_X86_VMX_INSN_H
#define __KVM_X86_VMX_INSN_H
#include <linux/nospec.h>
#include <asm/vmx.h>
#include "vmx_onhyperv.h"
#include "vmcs.h"
#include "../x86.h"
void vmread_error(unsigned long field);
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);
#ifndef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
/*
* The VMREAD error trampoline _always_ uses the stack to pass parameters, even
* for 64-bit targets. Preserving all registers allows the VMREAD inline asm
* blob to avoid clobbering GPRs, which in turn allows the compiler to better
* optimize sequences of VMREADs.
*
* Declare the trampoline as an opaque label as it's not safe to call from C
* code; there is no way to tell the compiler to pass params on the stack for
* 64-bit targets.
*
* void vmread_error_trampoline(unsigned long field, bool fault);
*/
extern unsigned long vmread_error_trampoline;
/*
* The second VMREAD error trampoline, called from the assembly trampoline,
* exists primarily to enable instrumentation for the VM-Fail path.
*/
void vmread_error_trampoline2(unsigned long field, bool fault);
#endif
static __always_inline void vmcs_check16(unsigned long field)
{
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2000,
"16-bit accessor invalid for 64-bit field");
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2001,
"16-bit accessor invalid for 64-bit high field");
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x4000,
"16-bit accessor invalid for 32-bit high field");
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x6000,
"16-bit accessor invalid for natural width field");
}
static __always_inline void vmcs_check32(unsigned long field)
{
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0,
"32-bit accessor invalid for 16-bit field");
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2000,
"32-bit accessor invalid for 64-bit field");
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2001,
"32-bit accessor invalid for 64-bit high field");
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x6000,
"32-bit accessor invalid for natural width field");
}
static __always_inline void vmcs_check64(unsigned long field)
{
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0,
"64-bit accessor invalid for 16-bit field");
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2001,
"64-bit accessor invalid for 64-bit high field");
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x4000,
"64-bit accessor invalid for 32-bit field");
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x6000,
"64-bit accessor invalid for natural width field");
}
static __always_inline void vmcs_checkl(unsigned long field)
{
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0,
"Natural width accessor invalid for 16-bit field");
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2000,
"Natural width accessor invalid for 64-bit field");
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6001) == 0x2001,
"Natural width accessor invalid for 64-bit high field");
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x4000,
"Natural width accessor invalid for 32-bit field");
}
static __always_inline unsigned long __vmcs_readl(unsigned long field)
{
unsigned long value;
#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
asm_goto_output("1: vmread %[field], %[output]\n\t"
"jna %l[do_fail]\n\t"
_ASM_EXTABLE(1b, %l[do_exception])
: [output] "=r" (value)
: [field] "r" (field)
: "cc"
: do_fail, do_exception);
return value;
do_fail:
instrumentation_begin();
vmread_error(field);
instrumentation_end();
return 0;
do_exception:
kvm_spurious_fault();
return 0;
#else /* !CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
asm volatile("1: vmread %2, %1\n\t"
".byte 0x3e\n\t" /* branch taken hint */
"ja 3f\n\t"
/*
* VMREAD failed. Push '0' for @fault, push the failing
* @field, and bounce through the trampoline to preserve
* volatile registers.
*/
"xorl %k1, %k1\n\t"
"2:\n\t"
"push %1\n\t"
"push %2\n\t"
"call vmread_error_trampoline\n\t"
/*
* Unwind the stack. Note, the trampoline zeros out the
* memory for @fault so that the result is '0' on error.
*/
"pop %2\n\t"
"pop %1\n\t"
"3:\n\t"
/* VMREAD faulted. As above, except push '1' for @fault. */
_ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_ONE_REG, %1)
: ASM_CALL_CONSTRAINT, "=&r"(value) : "r"(field) : "cc");
return value;
#endif /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
}
static __always_inline u16 vmcs_read16(unsigned long field)
{
vmcs_check16(field);
if (kvm_is_using_evmcs())
return evmcs_read16(field);
return __vmcs_readl(field);
}
static __always_inline u32 vmcs_read32(unsigned long field)
{
vmcs_check32(field);
if (kvm_is_using_evmcs())
return evmcs_read32(field);
return __vmcs_readl(field);
}
static __always_inline u64 vmcs_read64(unsigned long field)
{
vmcs_check64(field);
if (kvm_is_using_evmcs())
return evmcs_read64(field);
#ifdef CONFIG_X86_64
return __vmcs_readl(field);
#else
return __vmcs_readl(field) | ((u64)__vmcs_readl(field+1) << 32);
#endif
}
static __always_inline unsigned long vmcs_readl(unsigned long field)
{
vmcs_checkl(field);
if (kvm_is_using_evmcs())
return evmcs_read64(field);
return __vmcs_readl(field);
}
#define vmx_asm1(insn, op1, error_args...) \
do { \
asm 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: \
instrumentation_begin(); \
insn##_error(error_args); \
instrumentation_end(); \
return; \
fault: \
kvm_spurious_fault(); \
} while (0)
#define vmx_asm2(insn, op1, op2, error_args...) \
do { \
asm 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: \
instrumentation_begin(); \
insn##_error(error_args); \
instrumentation_end(); \
return; \
fault: \
kvm_spurious_fault(); \
} while (0)
static __always_inline void __vmcs_writel(unsigned long field, unsigned long value)
{
vmx_asm2(vmwrite, "r"(field), "rm"(value), field, value);
}
static __always_inline void vmcs_write16(unsigned long field, u16 value)
{
vmcs_check16(field);
if (kvm_is_using_evmcs())
return evmcs_write16(field, value);
__vmcs_writel(field, value);
}
static __always_inline void vmcs_write32(unsigned long field, u32 value)
{
vmcs_check32(field);
if (kvm_is_using_evmcs())
return evmcs_write32(field, value);
__vmcs_writel(field, value);
}
static __always_inline void vmcs_write64(unsigned long field, u64 value)
{
vmcs_check64(field);
if (kvm_is_using_evmcs())
return evmcs_write64(field, value);
__vmcs_writel(field, value);
#ifndef CONFIG_X86_64
__vmcs_writel(field+1, value >> 32);
#endif
}
static __always_inline void vmcs_writel(unsigned long field, unsigned long value)
{
vmcs_checkl(field);
if (kvm_is_using_evmcs())
return evmcs_write64(field, value);
__vmcs_writel(field, value);
}
static __always_inline void vmcs_clear_bits(unsigned long field, u32 mask)
{
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x2000,
"vmcs_clear_bits does not support 64-bit fields");
if (kvm_is_using_evmcs())
return evmcs_write32(field, evmcs_read32(field) & ~mask);
__vmcs_writel(field, __vmcs_readl(field) & ~mask);
}
static __always_inline void vmcs_set_bits(unsigned long field, u32 mask)
{
BUILD_BUG_ON_MSG(__builtin_constant_p(field) && ((field) & 0x6000) == 0x2000,
"vmcs_set_bits does not support 64-bit fields");
if (kvm_is_using_evmcs())
return evmcs_write32(field, evmcs_read32(field) | mask);
__vmcs_writel(field, __vmcs_readl(field) | mask);
}
static inline void vmcs_clear(struct vmcs *vmcs)
{
u64 phys_addr = __pa(vmcs);
vmx_asm1(vmclear, "m"(phys_addr), vmcs, phys_addr);
}
static inline void vmcs_load(struct vmcs *vmcs)
{
u64 phys_addr = __pa(vmcs);
if (kvm_is_using_evmcs())
return evmcs_load(phys_addr);
vmx_asm1(vmptrld, "m"(phys_addr), vmcs, phys_addr);
}
static inline void __invvpid(unsigned long ext, u16 vpid, gva_t gva)
{
struct {
u64 vpid : 16;
u64 rsvd : 48;
u64 gva;
} operand = { vpid, 0, gva };
vmx_asm2(invvpid, "r"(ext), "m"(operand), ext, vpid, gva);
}
static inline void __invept(unsigned long ext, u64 eptp, gpa_t gpa)
{
struct {
u64 eptp, gpa;
} operand = {eptp, gpa};
vmx_asm2(invept, "r"(ext), "m"(operand), ext, eptp, gpa);
}
static inline void vpid_sync_vcpu_single(int vpid)
{
if (vpid == 0)
return;
__invvpid(VMX_VPID_EXTENT_SINGLE_CONTEXT, vpid, 0);
}
static inline void vpid_sync_vcpu_global(void)
{
__invvpid(VMX_VPID_EXTENT_ALL_CONTEXT, 0, 0);
}
static inline void vpid_sync_context(int vpid)
{
if (cpu_has_vmx_invvpid_single())
vpid_sync_vcpu_single(vpid);
else if (vpid != 0)
vpid_sync_vcpu_global();
}
static inline void vpid_sync_vcpu_addr(int vpid, gva_t addr)
{
if (vpid == 0)
return;
if (cpu_has_vmx_invvpid_individual_addr())
__invvpid(VMX_VPID_EXTENT_INDIVIDUAL_ADDR, vpid, addr);
else
vpid_sync_context(vpid);
}
static inline void ept_sync_global(void)
{
__invept(VMX_EPT_EXTENT_GLOBAL, 0, 0);
}
static inline void ept_sync_context(u64 eptp)
{
if (cpu_has_vmx_invept_context())
__invept(VMX_EPT_EXTENT_CONTEXT, eptp, 0);
else
ept_sync_global();
}
#endif /* __KVM_X86_VMX_INSN_H */