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authorLinus Torvalds <torvalds@linux-foundation.org>2022-03-20 09:46:52 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-20 09:46:52 -0700
commit7445b2dcd77ae8385bd08bb6c2db20ea0cfa6230 (patch)
tree8af8eb7d511f9f2aa44c69289e2e255b347eac5a
parent1e0e7a6a28f877312b93cd12a1448c8d53733b55 (diff)
parentfe83f5eae432ccc8e90082d6ed506d5233547473 (diff)
downloadlinux-7445b2dcd77ae8385bd08bb6c2db20ea0cfa6230.tar.gz
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
-rw-r--r--arch/x86/kvm/emulate.c19
1 files changed, 17 insertions, 2 deletions
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 5719d8cfdbd9..e86d610dc6b7 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -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