On Wed, Apr 23, 2025, Manali Shukla wrote:
On 4/16/2025 11:30 AM, Xiaoyao Li wrote:
+ if (cpu_feature_enabled(X86_FEATURE_BUS_LOCK_THRESHOLD)) { + pr_info("Bus Lock Threshold supported\n");
It will be printed every time kvm-amd.ko module gets loaded.
I think it's for your development and debug purpose. Comparing to the existing features in svm_set_cpu_caps(), nothing makes it special for BUS_LOCK_THRESHOLD to require a kernel message. So I think we can just remove it.
I didn't add this for development and debug purpose. I added this pr_info() to make it easy to find whether BUS Lock threshold is supported or not from dmesg. I can remove it if you think it is not required.
Please remove it. The user typically doesn't care.
+ kvm_caps.has_bus_lock_exit = true;
Besides, this patch doesn't ensure the bisectability. It allows userspace to enable KVM_BUS_LOCK_DETECTION_EXIT and set intercept of INTERCEPT_BUSLOCK but without providing the handler.
So either move next patch before it or just merge them.
Oh.., my bad, I will move the next patch before this one in v5.
No, do exactly as I suggested in v3.
: I vote to split this into two patches: one to add the architectural collateral, : with the above as the changelog, and a second to actually implement support in : KVM. Having the above background is useful, but it makes it quite hard to find : information on the KVM design and implementation.
I want this (and any other arch collateral I'm missing) in a separate patch so that the background on what the hardware feature does is captured. But I see no reason to split KVM's implementation into multiple patches.
diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h index 2b59b9951c90..d1819c564b1c 100644 --- a/arch/x86/include/asm/svm.h +++ b/arch/x86/include/asm/svm.h @@ -116,6 +116,7 @@ enum { INTERCEPT_INVPCID, INTERCEPT_MCOMMIT, INTERCEPT_TLBSYNC, + INTERCEPT_BUSLOCK, };
@@ -158,7 +159,9 @@ struct __attribute__ ((__packed__)) vmcb_control_area { u64 avic_physical_id; /* Offset 0xf8 */ u8 reserved_7[8]; u64 vmsa_pa; /* Used for an SEV-ES guest */ - u8 reserved_8[720]; + u8 reserved_8[16]; + u16 bus_lock_counter; /* Offset 0x120 */ + u8 reserved_9[702]; /* * Offset 0x3e0, 32 bytes reserved * for use by hypervisor/software. diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h index 1814b413fd57..abf6aed88cee 100644 --- a/arch/x86/include/uapi/asm/svm.h +++ b/arch/x86/include/uapi/asm/svm.h @@ -95,6 +95,7 @@ #define SVM_EXIT_CR14_WRITE_TRAP 0x09e #define SVM_EXIT_CR15_WRITE_TRAP 0x09f #define SVM_EXIT_INVPCID 0x0a2 +#define SVM_EXIT_BUS_LOCK 0x0a5 #define SVM_EXIT_NPF 0x400 #define SVM_EXIT_AVIC_INCOMPLETE_IPI 0x401 #define SVM_EXIT_AVIC_UNACCELERATED_ACCESS 0x402 @@ -224,6 +225,7 @@ { SVM_EXIT_CR4_WRITE_TRAP, "write_cr4_trap" }, \ { SVM_EXIT_CR8_WRITE_TRAP, "write_cr8_trap" }, \ { SVM_EXIT_INVPCID, "invpcid" }, \ + { SVM_EXIT_BUS_LOCK, "buslock" }, \ { SVM_EXIT_NPF, "npf" }, \ { SVM_EXIT_AVIC_INCOMPLETE_IPI, "avic_incomplete_ipi" }, \ { SVM_EXIT_AVIC_UNACCELERATED_ACCESS, "avic_unaccelerated_access" }, \