On 11/21/22 1:44 AM, Huang, Kai wrote: > On Sun, 2022-11-20 at 19:51 -0800, Sathyanarayanan Kuppuswamy wrote: >> >> 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? > > It was quoted from below upstream commit id (I only kept the one that I quoted > to save space): Ok. > > commit b8d1d163604bd1e600b062fb00de5dc42baa355f (tag: x86_apic_for_v6.1_rc1, > tip/x86/apic) > Author: Daniel Sneddon <daniel.sneddon@xxxxxxxxxxxxxxx> > Date: Tue Aug 16 16:19:42 2022 -0700 > > x86/apic: Don't disable x2APIC if locked > > .... > > The MMIO/xAPIC interface has some problems, most notably the APIC LEAK > [1]. This bug allows an attacker to use the APIC MMIO interface to > extract data from the SGX enclave. > > .... > > [1]: https://aepicleak.com/aepicleak.pdf > > Signed-off-by: Daniel Sneddon <daniel.sneddon@xxxxxxxxxxxxxxx> > Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > Acked-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> > Tested-by: Neelima Krishnan <neelima.krishnan@xxxxxxxxx> > Link: > https://lkml.kernel.org/r/20220816231943.1152579-1-daniel.sneddon@xxxxxxxxxxxxxxx > > >> >>> [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. > > Sorry which "double space"? Before Just disable. It looked like double space. Is it not? > >> >>> + */ >>> + if (!x2apic_enabled()) { >>> + pr_info("Disable TDX as X2APIC is not enabled.\n"); >> >> pr_warn()? > > Why? Since it is a failure case, I thought pr_warn would be better. It is up to you. > -- Sathyanarayanan Kuppuswamy Linux Kernel Developer
