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x86/fsgsbase: Fix Xen PV support 

On Xen PV, SWAPGS doesn't work.  Teach __rdfsbase_inactive() and
__wrgsbase_inactive() to use rdmsrl()/wrmsrl() on Xen PV.  The Xen
pvop code will understand this and issue the correct hypercalls.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/f07c08f178fe9711915862b656722a207cd52c28.1593192140.git.luto@kernel.org
This commit is contained in:
Andy Lutomirski 2020-06-26 10:24:30 -07:00 committed by Thomas Gleixner
parent 40c45904f8
commit d029bff60a
1 changed files with 18 additions and 6 deletions
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24
arch/x86/kernel/process_64.c
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@ -163,9 +163,15 @@ static noinstr unsigned long __rdgsbase_inactive(void)
lockdep_assert_irqs_disabled();
native_swapgs();
gsbase = rdgsbase();
native_swapgs();
if (!static_cpu_has(X86_FEATURE_XENPV)) {
native_swapgs();
gsbase = rdgsbase();
native_swapgs();
} else {
instrumentation_begin();
rdmsrl(MSR_KERNEL_GS_BASE, gsbase);
instrumentation_end();
}
return gsbase;
}
@ -182,9 +188,15 @@ static noinstr void __wrgsbase_inactive(unsigned long gsbase)
{
lockdep_assert_irqs_disabled();
native_swapgs();
wrgsbase(gsbase);
native_swapgs();
if (!static_cpu_has(X86_FEATURE_XENPV)) {
native_swapgs();
wrgsbase(gsbase);
native_swapgs();
} else {
instrumentation_begin();
wrmsrl(MSR_KERNEL_GS_BASE, gsbase);
instrumentation_end();
}
}
/*