[PATCH for-4.7] x86/spec-ctrl: Fix backport of 1fdb25a614b

[PATCH for-4.7] x86/spec-ctrl: Fix backport of 1fdb25a614b

[Andrew Cooper]

Refreshing XenServer's patchqueue has shown that I missed this adjustment in
the upstream backports of the final version of the XSA-273 fixes.

The code does work in 4.7 and earlier, but only because the eventual value of
(opt_pv_l1tf & OPT_PV_L1TF_DOMx) is within range of a char.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
---
 xen/include/asm-x86/shadow.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/include/asm-x86/shadow.h b/xen/include/asm-x86/shadow.h
index de09e81..c720008 100644
--- a/xen/include/asm-x86/shadow.h
+++ b/xen/include/asm-x86/shadow.h
@@ -215,8 +215,8 @@ void pv_l1tf_tasklet(unsigned long data);
 static inline void pv_l1tf_domain_init(struct domain *d)
 {
     d->arch.pv_domain.check_l1tf =
-        opt_pv_l1tf & (is_hardware_domain(d)
-                       ? OPT_PV_L1TF_DOM0 : OPT_PV_L1TF_DOMU);
+        !!(opt_pv_l1tf & (is_hardware_domain(d)
+                          ? OPT_PV_L1TF_DOM0 : OPT_PV_L1TF_DOMU));
 
 #ifdef CONFIG_SHADOW_PAGING
     tasklet_init(&d->arch.paging.shadow.pv_l1tf_tasklet,
-- 
2.1.4


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Re: [PATCH for-4.7] x86/spec-ctrl: Fix backport of 1fdb25a614b

[Jan Beulich]

>>> On 30.08.18 at 20:37, <andrew.cooper3@citrix.com> wrote:
> Refreshing XenServer's patchqueue has shown that I missed this adjustment in
> the upstream backports of the final version of the XSA-273 fixes.
> 
> The code does work in 4.7 and earlier, but only because the eventual value of
> (opt_pv_l1tf & OPT_PV_L1TF_DOMx) is within range of a char.

And I had noticed this while pulling things into our trees, but decided
to leave it since it's working.

> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Acked-by: Jan Beulich <jbeulich@suse.com>

Jan



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Re: [PATCH for-4.7] x86/spec-ctrl: Fix backport of 1fdb25a614b

[Andrew Cooper]

On 31/08/18 08:24, Jan Beulich wrote:
>>>> On 30.08.18 at 20:37, <andrew.cooper3@citrix.com> wrote:
>> Refreshing XenServer's patchqueue has shown that I missed this adjustment in
>> the upstream backports of the final version of the XSA-273 fixes.
>>
>> The code does work in 4.7 and earlier, but only because the eventual value of
>> (opt_pv_l1tf & OPT_PV_L1TF_DOMx) is within range of a char.
> And I had noticed this while pulling things into our trees, but decided
> to leave it since it's working.
>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> Acked-by: Jan Beulich <jbeulich@suse.com>

I figured that, especially as you've got a patch proposing to change
these constants, that it would be safer to make it work now.

~Andrew

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