Commit 7445b2dc authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'for-linus-5.17' of git://git.kernel.org/pub/scm/virt/kvm/kvm 

Pull kvm fix from Paolo Bonzini:
 "Fix for the SLS mitigation, which makes a 'SETcc/RET' pair grow
  to 'SETcc/RET/INT3'.

  This doesn't fit in 4 bytes any more, so the alignment has to
  change to 8 for this case"

* tag 'for-linus-5.17' of git://git.kernel.org/pub/scm/virt/kvm/kvm:
  kvm/emulate: Fix SETcc emulation function offsets with SLS
parents 1e0e7a6a fe83f5ea

arch/x86/kvm/emulate.c

+17 −2
Original line number Diff line number Diff line
@@ -429,8 +429,23 @@ static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop); 
	FOP_END



/* Special case for SETcc - 1 instruction per cc */



/*

 * Depending on .config the SETcc functions look like:

 *

 * SETcc %al   [3 bytes]

 * RET         [1 byte]

 * INT3        [1 byte; CONFIG_SLS]

 *

 * Which gives possible sizes 4 or 5.  When rounded up to the

 * next power-of-two alignment they become 4 or 8.

 */

#define SETCC_LENGTH	(4 + IS_ENABLED(CONFIG_SLS))

#define SETCC_ALIGN	(4 << IS_ENABLED(CONFIG_SLS))

static_assert(SETCC_LENGTH <= SETCC_ALIGN);



#define FOP_SETCC(op) \

	".align 4 \n\t" \

	".align " __stringify(SETCC_ALIGN) " \n\t" \

	".type " #op ", @function \n\t" \

	#op ": \n\t" \

	#op " %al \n\t" \
@@ -1047,7 +1062,7 @@ static int em_bsr_c(struct x86_emulate_ctxt *ctxt) 
static __always_inline u8 test_cc(unsigned int condition, unsigned long flags)

{

	u8 rc;

	void (*fop)(void) = (void *)em_setcc + 4 * (condition & 0xf);

	void (*fop)(void) = (void *)em_setcc + SETCC_ALIGN * (condition & 0xf);



	flags = (flags & EFLAGS_MASK) | X86_EFLAGS_IF;

	asm("push %[flags]; popf; " CALL_NOSPEC