set_xcr0() and set_msr_xss() use cached value to avoid setting the register to the same value over and over. But suspend/resume implicitly reset the registers and since percpu areas are not deallocated on suspend anymore, the cache gets stale. Reset the cache on resume, to ensure the next write will really hit the hardware. Choose value 0, as it will never be a legitimate write to those registers - and so, will force write (and cache update).
Note the cache is used io get_xcr0() and get_msr_xss() too, but: - set_xcr0() is called few lines below in xstate_init(), so it will update the cache with appropriate value - get_msr_xss() is not used anywhere - and thus not before any set_msr_xss() that will fill the cache Fixes: aca2a985a55a "xen: don't free percpu areas during suspend" Signed-off-by: Marek Marczykowski-Górecki <[email protected]> --- xen/arch/x86/xstate.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c index 6aaf9a2f1546..28726d8fbf2b 100644 --- a/xen/arch/x86/xstate.c +++ b/xen/arch/x86/xstate.c @@ -642,6 +642,13 @@ void xstate_init(struct cpuinfo_x86 *c) return; } + /* + * Clear the cached value to make set_xcr0() and set_msr_xss() really + * write it. + */ + this_cpu(xcr0) = 0; + this_cpu(xss) = 0; + cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx); feature_mask = (((u64)edx << 32) | eax) & XCNTXT_MASK; BUG_ON(!valid_xcr0(feature_mask)); -- 2.31.1
