2018年2月14日 19:10于 Andrew Cooper <andrew.coop...@citrix.com>写道： > > DO_OVERWRITE_RSB clobbers %rax, meaning in practice that that the > bti_ist_info > field gets zeroed. Older versions of this code had the DO_OVERWRITE_RSB > register selectable, so reintroduce this ability and use it to cause the > INTR_IST path to use %rdx instead. > > The use of %dl for the %cs.rpl check means that when an IST interrupt hits > Xen, we try to load 1 into the high 32 bits of MSR_SPEC_CTRL, suffering a #GP > fault instead. > > Also, drop an unused label which was a copy/paste mistake. > > Reported-by: Boris Ostrovsky <boris.ostrov...@oracle.com> > Reported-by: Zhenzhong Duan <zhenzhong.d...@oracle.com> > Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com> > --- > CC: Jan Beulich <jbeul...@suse.com> > CC: Zhenzhong Duan <zhenzhong.d...@oracle.com> > CC: Boris Ostrovsky <boris.ostrov...@oracle.com> > CC: Wei Liu <wei.l...@citrix.com> > CC: Roger Pau Monné <roger....@citrix.com> > --- > xen/include/asm-x86/spec_ctrl_asm.h | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/xen/include/asm-x86/spec_ctrl_asm.h > b/xen/include/asm-x86/spec_ctrl_asm.h > index 814f53d..1f78599 100644 > --- a/xen/include/asm-x86/spec_ctrl_asm.h > +++ b/xen/include/asm-x86/spec_ctrl_asm.h > @@ -79,10 +79,10 @@ > * - SPEC_CTRL_EXIT_TO_GUEST > */ > > -.macro DO_OVERWRITE_RSB > +.macro DO_OVERWRITE_RSB tmp=%rax > /* > * Requires nothing > - * Clobbers %rax, %rcx > + * Clobbers \tmp (%rax by default), %rcx > * > * Requires 256 bytes of stack space, but %rsp has no net change. Based on > * Google's performance numbers, the loop is unrolled to 16 iterations and > two > @@ -97,7 +97,7 @@ > * optimised with mov-elimination in modern cores. > */ > mov $16, %ecx /* 16 iterations, two calls per loop */ > - mov %rsp, %rax /* Store the current %rsp */ > + mov %rsp, \tmp /* Store the current %rsp */ > > .L\@_fill_rsb_loop: > > @@ -114,7 +114,7 @@ > > sub $1, %ecx > jnz .L\@_fill_rsb_loop > - mov %rax, %rsp /* Restore old %rsp */ > + mov \tmp, %rsp /* Restore old %rsp */ > .endm > > .macro DO_SPEC_CTRL_ENTRY_FROM_VMEXIT ibrs_val:req > @@ -274,7 +274,7 @@ > testb $BTI_IST_RSB, %al > jz .L\@_skip_rsb > > - DO_OVERWRITE_RSB > + DO_OVERWRITE_RSB tmp=%rdx /* Clobbers %ecx/%rdx */ > > .L\@_skip_rsb: > > @@ -286,13 +286,13 @@ > setz %dl > and %dl, STACK_CPUINFO_FIELD(use_shadow_spec_ctrl)(%r14) Is it safe to remove the 'xor %edx, %edx' above? setz set whole byte 1 or 0. --- thanks zduan
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