On 11/20/22 4:26 PM, Kai Huang wrote: > The MMIO/xAPIC interface has some problems, most notably the APIC LEAK "some problems" looks more generic. May be we can be specific here. Like it has security issues? > [1]. This bug allows an attacker to use the APIC MMIO interface to > extract data from the SGX enclave. > > TDX is not immune from this either. Early check X2APIC and disable TDX > if X2APIC is not enabled, and make INTEL_TDX_HOST depend on X86_X2APIC. > > [1]: https://aepicleak.com/aepicleak.pdf > > Link: https://lore.kernel.org/lkml/d6ffb489-7024-ff74-bd2f-d1e06573bb82@xxxxxxxxx/ > Link: https://lore.kernel.org/lkml/ba80b303-31bf-d44a-b05d-5c0f83038798@xxxxxxxxx/ > Signed-off-by: Kai Huang <kai.huang@xxxxxxxxx> > --- > > v6 -> v7: > - Changed to use "Link" for the two lore links to get rid of checkpatch > warning. > > --- > arch/x86/Kconfig | 1 + > arch/x86/virt/vmx/tdx/tdx.c | 11 +++++++++++ > 2 files changed, 12 insertions(+) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index cced4ef3bfb2..dd333b46fafb 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -1958,6 +1958,7 @@ config INTEL_TDX_HOST > depends on CPU_SUP_INTEL > depends on X86_64 > depends on KVM_INTEL > + depends on X86_X2APIC > help > Intel Trust Domain Extensions (TDX) protects guest VMs from malicious > host and certain physical attacks. This option enables necessary TDX > diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c > index 982d9c453b6b..8d943bdc8335 100644 > --- a/arch/x86/virt/vmx/tdx/tdx.c > +++ b/arch/x86/virt/vmx/tdx/tdx.c > @@ -12,6 +12,7 @@ > #include <linux/printk.h> > #include <asm/msr-index.h> > #include <asm/msr.h> > +#include <asm/apic.h> > #include <asm/tdx.h> > #include "tdx.h" > > @@ -81,6 +82,16 @@ static int __init tdx_init(void) > goto no_tdx; > } > > + /* > + * TDX requires X2APIC being enabled to prevent potential data > + * leak via APIC MMIO registers. Just disable TDX if not using > + * X2APIC. Remove the double space. > + */ > + if (!x2apic_enabled()) { > + pr_info("Disable TDX as X2APIC is not enabled.\n"); pr_warn()? > + goto no_tdx; > + } > + > return 0; > no_tdx: > clear_tdx(); -- Sathyanarayanan Kuppuswamy Linux Kernel Developer
