Re: [RFC PATCH v3 02/59] x86/mtrr: mask out keyid bits from variable mtrr mask register

Re: [RFC PATCH v3 02/59] x86/mtrr: mask out keyid bits from variable mtrr mask register

[Thomas Gleixner]

On Thu, Nov 25 2021 at 09:36, Thomas Gleixner wrote:
>>  
>> +			if (boot_cpu_has(X86_FEATURE_TME)) {

cpu_feature_enabled() as Borislav pointed out several times already.

>> +				u64 tme_activate;
>> +
>> +				rdmsrl(MSR_IA32_TME_ACTIVATE, tme_activate);
>> +				if (TME_ACTIVATE_LOCKED(tme_activate) &&
>> +				    TME_ACTIVATE_ENABLED(tme_activate)) {
>> +					phys_addr -= TME_ACTIVATE_KEYID_BITS(tme_activate);
>> +				}
>> +			}
>>  			size_or_mask = SIZE_OR_MASK_BITS(phys_addr);
>>  			size_and_mask = ~size_or_mask & 0xfffff00000ULL;
>>  		} else if (boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR &&

[RFC PATCH v3 02/59] x86/mtrr: mask out keyid bits from variable mtrr mask register

[isaku.yamahata]

From: Isaku Yamahata <isaku.yamahata@intel.com>

This is a preparation for TDX support. TDX repurposes high bits of physcial
address to private key ID similarly to MKTME.
IA32_TME_ACTIVATE.MK_TME_KEYID_BITS has same meaning for both TDX
disabled/enable for compatibility.

MTRR calculates mask based on available physical address bits.  MKTME
repurpose high bit of physical address to key id for key id.  CPUID MAX_PA
remains same and the bits stolen for key id is controlled IA32_TME_ACTIVATE
MSR bit 35:32.  Because Key ID bits shouldn't affects memory cachability,
MTRR mask should exclude bits repourposed for Key ID.  It's OS
responsibility to maintain cache coherency.  detect_tme @
arch/x86/kernel/cpu/intel.c detects tme and destract it from total usable
physical bits. This patch adds same logic needed for MTRR.

Co-developed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
---
 arch/x86/kernel/cpu/mtrr/mtrr.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.c b/arch/x86/kernel/cpu/mtrr/mtrr.c
index 2746cac9d8a9..79eaf6ed20a6 100644
--- a/arch/x86/kernel/cpu/mtrr/mtrr.c
+++ b/arch/x86/kernel/cpu/mtrr/mtrr.c
@@ -713,6 +713,15 @@ void __init mtrr_bp_init(void)
 			     boot_cpu_data.x86_stepping == 0x4))
 				phys_addr = 36;
 
+			if (boot_cpu_has(X86_FEATURE_TME)) {
+				u64 tme_activate;
+
+				rdmsrl(MSR_IA32_TME_ACTIVATE, tme_activate);
+				if (TME_ACTIVATE_LOCKED(tme_activate) &&
+				    TME_ACTIVATE_ENABLED(tme_activate)) {
+					phys_addr -= TME_ACTIVATE_KEYID_BITS(tme_activate);
+				}
+			}
 			size_or_mask = SIZE_OR_MASK_BITS(phys_addr);
 			size_and_mask = ~size_or_mask & 0xfffff00000ULL;
 		} else if (boot_cpu_data.x86_vendor == X86_VENDOR_CENTAUR &&
-- 
2.25.1