From daaf007eb3467f900a2e20fadbc4c6f3bfcaa356 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Mon, 30 Aug 2021 15:19:31 +0200 Subject: [PATCH] libxenguest/x86: ensure CPUID[1].EBX[32:16] is non-zero for HVM We unconditionally set HTT, so merely doubling the value read from hardware isn't going to be correct if that value is zero. Reported-by: Julien Grall Signed-off-by: Jan Beulich Tested-by: Julien Grall Acked-by: Andrew Cooper --- tools/libs/guest/xg_cpuid_x86.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/tools/libs/guest/xg_cpuid_x86.c b/tools/libs/guest/xg_cpuid_x86.c index 0c9c4fefc1..198892ebdf 100644 --- a/tools/libs/guest/xg_cpuid_x86.c +++ b/tools/libs/guest/xg_cpuid_x86.c @@ -594,7 +594,9 @@ int xc_cpuid_apply_policy(xc_interface *xch, uint32_t domid, bool restore, * Update to reflect vLAPIC_ID = vCPU_ID * 2, but make sure to avoid * overflow. */ - if ( !(p->basic.lppp & 0x80) ) + if ( !p->basic.lppp ) + p->basic.lppp = 2; + else if ( !(p->basic.lppp & 0x80) ) p->basic.lppp *= 2; switch ( p->x86_vendor ) -- 2.30.2